tag:blogger.com,1999:blog-286253842024-03-13T18:47:20.621-04:00Exploding Galaxies and other CatastrophysicsNotes about astrophysics (including superwinds, of course), and occasionally other science or science-politics I think is interesting.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.comBlogger379125tag:blogger.com,1999:blog-28625384.post-92155515250100754052024-02-25T09:29:00.004-05:002024-02-25T09:29:28.613-05:00More WIP AstroPhotographyAfter a long hiatus I've restarted effort on my own set of <a href="https://github.com/DaveStrickland/AstroPhotography" target="_blank">python tools for amateur astronomical data reduction</a>. Here is a work in progress output from combining the very short set of SN 2023ixf images provied as part of the iTelesop Plan-20 Premium image set.
Taken with iTelescope T24. 3x FITS images each of 300s Red, Green, Blue filter. iTelescope stock calibration, so there may be some residual bad pixels. Astrometric solution using Astromatic.net, and images realigned to North up, East to the left, with 0.62 arcseconds per pixel.
Net exposure 15 minutes in each filter.
RGB PNG generated by stiff, wavelet denoised in the gimp. Of course three images in each filter is much less data than needed for a serious product, but its ideal for testing my pipeline.
Click to embiggen: <a data-flickr-embed="true" href="https://www.flickr.com/photos/191916036@N05/53551272888/in/dateposted-public/" title="M101_Supernova_2023ixf_RedGreenBlue_4096x4096_resamp_median_gf10_cs20_b8"><img src="https://live.staticflickr.com/65535/53551272888_0be4dedcf0_b.jpg" width="1024" height="1010" alt="M101_Supernova_2023ixf_RedGreenBlue_4096x4096_resamp_median_gf10_cs20_b8"/></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-62813110554508129562021-08-29T14:24:00.002-04:002021-08-29T14:24:56.746-04:00Work In Progress Astrophotography<p>Here are a few new amateur astronomical images I've been working on. These are very much a work in progress, in particular with handling the sky background when building up large mosiac images. These were taken using the <a href="https://www.itelescope.net/" target="_blank">iTelescope</a> T05 (a 250mm Takahashi reflector) and T20 (a 106mm APO refractor) telescopes in New Mexico over a series of nights this year, and processed using various <a href="https://github.com/DaveStrickland/AstroPhotography" target="_blank">python tools I wrote for the purpose</a>.</p>
<p>A 5x5 degrees SII, H-alpha and OIII mosaics of the Cygnus Loop supernova remnant, taken with T20.
<a data-flickr-embed="true" href="https://www.flickr.com/photos/191916036@N05/51410911588/in/dateposted-public/" title="CygnusLoop_SIIHaOIII_5000x5000_resamp_wgtavg_gf10_cs15_b8"><img src="https://live.staticflickr.com/65535/51410911588_49ab016d0a_b.jpg" width="1024" height="1024" alt="CygnusLoop_SIIHaOIII_5000x5000_resamp_wgtavg_gf10_cs15_b8"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>
The struggle with the images were taken when the Moon was up, even though the were taken over several days. Weather has been crummy at the NM site this summer, so you make do with what you get. But the sky backgrounds need some additional work.</p>
<p>The other images are of the NGC 6888 (shown previously), and M82 and/or M81, each taken separately with T05, and mosaiced together in some versions. The depth of the different images and bands varies a lot, for example there are 25 5-minute H-alpha images of M82, but only 6 5-minute H-alpha images of M81. I also messed up by using the Johnson-Cousins B filter on M81 when I've used the Astrodon Blue on M82.
<a data-flickr-embed="true" href="https://www.flickr.com/photos/191916036@N05/albums/72157718172793858" title="Astrophotography"><img src="https://live.staticflickr.com/65535/50911732797_a4fa58055f_c.jpg" width="768" height="1024" alt="Astrophotography"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script></p>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-16578573738862988882021-02-02T08:13:00.000-05:002021-02-02T08:13:50.975-05:00The Wolf-Rayet bubble NGC 6888<p> As a bit of amateur astronomy I signed up with iTelescope in July 2020, and took some images of NGC 6888, a favorite object of mine. It took several months to accumulate the set of images I wanted, and another several months to write the tools to process the raw data in the way I wanted, but finally here they are:</p><p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-ud1E2Pp2Ehg/YBk_NzWDK2I/AAAAAAAAOyA/A74RAsy89cEoqyNUBDM0aSTW1HzttWBDwCLcBGAsYHQ/s1920/n6888_SIIHaOIII_1920x1080_resamp_median_gf12_cs15_b8.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="NGC 6888 SII, H-alpha, OIII" border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-ud1E2Pp2Ehg/YBk_NzWDK2I/AAAAAAAAOyA/A74RAsy89cEoqyNUBDM0aSTW1HzttWBDwCLcBGAsYHQ/w640-h360/n6888_SIIHaOIII_1920x1080_resamp_median_gf12_cs15_b8.png" title="NGC 6888 in SII, H-alpha, and OIII filters" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">NGC 6888 taken in SII (red), H-alpha (green) and OIII (blue) filters.<br /></td></tr></tbody></table><br /><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-NBohI7pG0Gw/YBk_Rh2X-1I/AAAAAAAAOyE/ztI2CW30S7IYFKmOWpkmI16xcQyFmD-EwCLcBGAsYHQ/s1920/n6888_RedGreenBlue_1920x1080_resamp_median_gf14_cs15_b8.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="NGC 6888 Red Green Blue filters" border="0" data-original-height="1080" data-original-width="1920" height="360" src="https://1.bp.blogspot.com/-NBohI7pG0Gw/YBk_Rh2X-1I/AAAAAAAAOyE/ztI2CW30S7IYFKmOWpkmI16xcQyFmD-EwCLcBGAsYHQ/w640-h360/n6888_RedGreenBlue_1920x1080_resamp_median_gf14_cs15_b8.png" title="NGC 6888 in Astrodon Red, Green and Blue filters" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">NGC 6888 using Astrodon Red, Green and Blue filters.<br /></td></tr></tbody></table> </p><p>NGC 6888 is the wind blown bubble surrounding Wolf Rayet 136, at a distance of around 2,000 parsecs (6,500 light years) from us. WR 136 is an evolved massive star with a strong stellar wind (velocity approximately 1,500 km/s) that is blowing into the slower and denser ejecta from the star's previous Red Supergiant phase, creating a bubble approximately 10 pc x 7 pc in size (34 x 23 light years). WR 136 is the bright star at the center of the image. Although only about mV ~ 7.5, its intrinsic luminosity is approximately 500,000 times that of the Sun, and its effective temperature is 70 to 80 thousand degrees Kelvin, </p><p>The nebula emission seen in these images is almost exclusively swept-up and compressed RSG wind material, that has been photo-ionized by the WR star. The WR wind material inflating the bubble is shock-heated to million degree temperatures, and hence is not visible in these images. There are of course X-ray images of this hot gas, although the Chandra and XMM-Newton images only partly cover the bubble (given those observatories small field of view), and absorption from intervening interstellar gas and dust severely attenuates the soft X-ray emission. (I did a <a href="https://ui.adsabs.harvard.edu/abs/1998MNRAS.297..747S/abstract" target="_blank">theoretical paper that modeled NGC 6888</a> as part of my PhD thesis work at the University of Birmingham back in the mid 1990's.)</p><p>The bubble itself is relatively young, at least compared to million-year-old main-sequence massive star wind bubbles and superbubbles: with an expansion velocity of approximately 80 km/s its dynamical age is only about 50,000 years. The relatively short lifespan of the RSG/WR wind interaction probably explains why WR bubbles are only clearly seen around a small fraction of galactic WR stars.<br /></p><p>The hydro-dynamical instabilities caused by the interaction of the fast tenuous WR wind and the slow dense RSG wind are also the source of the beautiful substructure in the nebula, first demonstrated (I think) in some excellent papers by García-Segura and Mac Low in the mid 1990's [e.g. <a href="http://adsabs.harvard.edu/full/1995ApJ...455..160G" target="_blank">this paper</a>]. They are even more apparent in the <a href="https://hubblesite.org/contents/news-releases/2000/news-2000-23.html" target="_blank">Hubble Space Telescope images of a small region of the rim of the bubble</a>.<br /></p>Telescope and image information:<ul style="text-align: left;"><li>iTelescope T05 at New Mexico site (MPC H06)</li><li>Takahashi Epsilon 250 with Paramount PME mount and SBIG ST-10XME CCD.</li><li>Images taken on 2020-07-16, 2020-08-10, 2020-08-12, 2020-09-17 and 2020-10-16. <br /></li><li>Resampled images have 1.8 arcsecond square pixels aligned North at the top, East at the left, and cover a 0.96 degree x 0.54 degree FOV.</li><li>Net exposure time:</li><ul><li>SII/H-alpha/OIII image: 113 minutes<br /></li><li>Red/Green/Blue image: 18 minutes<br /></li></ul><li>Individual raw frames:</li><ul><li>SII/H-alpha/OIII image: SII 2x240s, 8x300s; H-alpha 9x180s; OIII 2x240s, 6x300s.<br /></li><li>Red/Green/Blue image: Red 6x60s; Green 6x60s; Blue 6x60s.<br /></li></ul><li>Measured effective Point Spread Function FWHM = 5.8 arcseconds, which on paper sounds pretty poor. </li><li>Processed from raw FITS images using my AstroPhotography python code (which uses astropy, photutils, ccdproc and Astrometry.net), some additional bash scripts, and Astromatic swarp (for resampling and co-addition) and stiff (for color image generation). No additional photoshop/gimp manipulation!<br /></li></ul><p><br /></p>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-50392589739893220472020-07-11T12:55:00.000-04:002020-07-11T12:55:36.088-04:00Comet 2020 F3 (NEOWISE)The long period comet C/2020 F3 (aka NEOWISE, named after the satellite that first detected it) is one of the most impressive comets in the last few decades.<br />
<br />
Although my attempts to see it personally have so far been frustrated by cloud and lack of clear sight lines to the north-east, I have been following the images of it that have appeared in <a href="https://apod.nasa.gov/apod/astropix.html" target="_blank">Astronomy Picture Of The Day (APOD)</a>. Most if not all of the images posted so far, or presented in pop sci articles online fail to tell you any quantitative details about what you're looking at, so I decided to work out some rough distances and sizes based on the <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=C%2F2020%20F3;old=0;orb=0;cov=0;log=0;cad=0" target="_blank">JPL Small Body Database info on NEOWISE</a>, and the image taken from the ISS on July 5th 2020, and the <a href="https://edu.kde.org/kstars/" target="_blank">kstars</a> desktop planetarium software.<br />
<br />
This image is a cropped, resized and annotated version of the <a href="https://apod.nasa.gov/apod/ap200710.html" target="_blank">ISS image posted at APOD</a> on July 10, 2020. I've labelled some of the prominent stars, although to a ground-based amateur observer the star Capella, which is hidden behind parts of the ISS off the top left of the image, would be the most most prominent star visible.<br />
<br />
From the JPL SBDB we can find that NEOWISE was about 0.3 AU from the Sun on 7/5/2020, and about 1.1 AU (approx 165 million km) from Earth. At a distance of 1.1 AU an angular distance of 1 degree is about 3 million km. <br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-d_FFu6NoGSQ/XwnuGa3g2mI/AAAAAAAAOaM/sFnZCcftXHISdmZfdyNtAeCeH6axPEbZACLcBGAsYHQ/s1600/ISS_CometNEOWISE_July2020_annotated.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="Comet C/2020 F3 (NEOWISE) as seen from the ISS on 7/5/2020" border="0" data-original-height="576" data-original-width="1024" height="360" src="https://1.bp.blogspot.com/-d_FFu6NoGSQ/XwnuGa3g2mI/AAAAAAAAOaM/sFnZCcftXHISdmZfdyNtAeCeH6axPEbZACLcBGAsYHQ/s640/ISS_CometNEOWISE_July2020_annotated.jpg" title="" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">My annotated version of APOD from 07/10/2020, <b>Image Credit: </b>
<a href="https://www.nasa.gov/">NASA</a>,
<a href="https://www.flickr.com/photos/nasa2explore/albums/72157713159009527/page1">ISS Expedition 63</a></td></tr>
</tbody></table>
<br />
The angular distance between <a href="https://en.wikipedia.org/wiki/Theta_Aurigae" target="_blank">Theta Aurigae</a> and <a href="https://en.wikipedia.org/wiki/Beta_Tauri" target="_blank">Elnath</a> is approximately 10.54 degrees, and the angular distance between Elnath and <a href="https://en.wikipedia.org/wiki/Iota_Aurigae" target="_blank">Kabdhiliinan</a> (Iota Aurigae) is approximately 7.76 degrees based on using a measuring tool in kstars. If we assume the ISS image is not significantly distorted then we can measure the number of pixels between the stars on the image and compare that to the length of the tail in the image to work out its angular size. In fact the image does seem to be be slightly distorted, but taking an average I get that the visible tail in this image is about 1.7 degrees long, so the visible tail is about 5 million km long. Its not every day you can go out and see something 5 million km in size!Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-30371317853043572832020-02-09T06:53:00.002-05:002020-02-09T06:53:19.001-05:00NASA Astrophoto Challenge for Winter 2019 is M82Noted with approval: the NASA Astrophoto challenge for Winter 2019 is my old friend Messier 82. See if you can create a press-release worthy image of M82 using either existing NASA images for different orbiting observatories and/or <a href="https://mo-www.cfa.harvard.edu/OWN/index.html" target="_blank">ground-based optical images taken at your request by Harvard's MicroObservatory service</a>.<br />
<br />
<iframe frameborder="0" height="400" src="https://mo-www.cfa.harvard.edu/OWN/astrophoto/" width="100%"></iframe>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-67863203409343509552019-08-22T18:55:00.002-04:002019-08-22T18:57:56.735-04:00Mauna KeaLooking toward the summit of Mauna Kea, from the small hill near the base of the access road. Taken in 2005.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-GFDMyxvs6RQ/XV8cnPk9gnI/AAAAAAAAKxI/z1PGJr4FPVETXX4E9PA8Zj_LwKaEOdJqACLcBGAs/s1600/2005_03_16_20_41_56_dave.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://1.bp.blogspot.com/-GFDMyxvs6RQ/XV8cnPk9gnI/AAAAAAAAKxI/z1PGJr4FPVETXX4E9PA8Zj_LwKaEOdJqACLcBGAs/s640/2005_03_16_20_41_56_dave.jpg" width="640" /></a></div>
A view from the summit, looking toward the Keck telescopes. Taken in 2005.<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://2.bp.blogspot.com/-qNm85EH9q3s/XV8cxEEoRII/AAAAAAAAKxM/LaDQR2fuXsE9zUgynENXNb01S9o_BujTQCLcBGAs/s1600/2005_03_16_22_47_18_dave.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://2.bp.blogspot.com/-qNm85EH9q3s/XV8cxEEoRII/AAAAAAAAKxM/LaDQR2fuXsE9zUgynENXNb01S9o_BujTQCLcBGAs/s640/2005_03_16_22_47_18_dave.jpg" width="640" /></a></div>
<br />Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-45676764263592230202018-07-07T07:53:00.000-04:002018-07-07T07:53:13.687-04:00Colorful binary star systems for small telescopes: Part 2I previously discussed my ongoing attempt to develop an automated method of getting the physical properties of binary/multiple star systems visible to amateur astronomers. In <a href="http://superwinds.blogspot.com/2018/03/colorful-binary-star-systems-for-small.html" target="_blank">Part 1</a> I got as far as getting basic observables and IDs for the Primary stars in Bob King's article,<a href="http://www.skyandtelescope.com/observing/colored-double-stars-real-and-imagined/" target="_blank">"Colored Double Stars, Real and Imagined" by Bob King (Sky & Telescope, December 14 2016</a>).<br />
<br />
The next step, described here, is to use the the <a href="http://ad.usno.navy.mil/wds/" target="_blank">Washington Double Star Catalog</a> to identify and list the probably companions of each Primary. The WDS is an ongoing project that summarizes observations of bright visual double or multiple stars. Their aim is to determine which, if any, are physically associated in a gravitationally bound stellar systems as opposed to being chance line of sight superpositions. As such the WDS project makes use of multiple historical observations, measured distances (by <a href="https://en.wikipedia.org/wiki/Stellar_parallax" target="_blank">parallax</a>) and <a href="https://en.wikipedia.org/wiki/Proper_motion" target="_blank">proper motions</a>, the results of which are summarized in their catalog.<br />
<br />
To cut a long story short I've written some bash and python scripts that download the latest WDS catalog from Vizier, then takes the outputs from the scripts described in Part 1 and combines that with the WDS catalog to come up with a list of Primary, Secondary, (Tertiary etc) stellar IDs based on some WDS-related selection criteria.<br />
<br />
I was surprised to find that even for many visually bright double stars their exact status, as genuine binary or multiple star systems or as chance line-of-sight superpositions, is not currently 100% known. In addition, for some "classic" doubles, the latest information suggests they are likely not genuine binaries. <br />
<br />
To illustrate this I'll continue to show examples based on Bob King's Colored Double Stars.<br />
<br />
Firstly, we'll select components where the WDS catalog notes that there is evidence consistent with them being members of the same physical stellar system.<br />
<br />
Then for purposes of comparison we'll separately select all WDS possible components but exclude those where there is evidence is against them being associated.<br />
<h3>
Filtering based on positive evidence for multiplicity</h3>
Here we are looking for double/multiple stellar systems where the available WDS info suggests they're real gravitationally bounds systems. To do this we select components with already determined actual orbits, or statistically similar parallax and/or proper motions (i.e. they're at close to the same distance and/or are moving in the sky in the same way). These correspond to the WDS 'Note' column entries 'C', 'O', 'T', 'V' or 'Z'.<br />
<br />
<pre>
python3 process_wds_ids.py king_processed.fits.gz king_wds_postv_ids.html \
--wds-detail=king_wds_postv_detail.html --filter=positive
[...output trimmed for blog...]
0 input targets with no WDS info: []
8 input targets where positive filtering removed all components: ['1 Ari',
'iota Tri = 6 Tri', 'eta Per', '32 Eri', 'rho Ori', 'iota Ori', 'gamma Lep',
'24 Com']
</pre>
<br />
This produced an HTML table of input star name and output component WDS IDs (king_wds_postv_ids.html), along with an optional separate table listing select information from the WDS catalog for each selected component (king_wds_postv_detail.html) which is shown below:<br />
<div class="horizontal">
<table class="darkTable">
<thead>
<tr>
<th>WDS</th>
<th>Comp</th>
<th>Obs2</th>
<th>pa2</th>
<th>sep2</th>
<th>mag1</th>
<th>mag2</th>
<th>SpType</th>
<th>Notes</th>
</tr>
</thead>
<tbody>
<tr>
<td>00491+5749</td>
<td>AB</td>
<td>2016</td>
<td>325</td>
<td>13.4</td>
<td>3.52</td>
<td>7.36</td>
<td>G1V+M</td>
<td>NO P</td>
</tr>
<tr>
<td>02039+4220</td>
<td>BC</td>
<td>2010</td>
<td>96</td>
<td>0.2</td>
<td>5.3</td>
<td>6.5</td>
<td>B8V+A0V</td>
<td>NO</td>
</tr>
<tr>
<td>05154+3241</td>
<td>Ca,Cb</td>
<td>1999</td>
<td>100</td>
<td>2.0</td>
<td>7.33</td>
<td>14.1</td>
<td>F2V+DA1.3</td>
<td>NV</td>
</tr>
<tr>
<td>07166-2319</td>
<td>BC</td>
<td>1999</td>
<td>165</td>
<td>999.9</td>
<td>5.84</td>
<td>6.76</td>
<td>A5m+F0</td>
<td>NV</td>
</tr>
<tr>
<td>08467+2846</td>
<td></td>
<td>2016</td>
<td>308</td>
<td>31.3</td>
<td>4.13</td>
<td>5.99</td>
<td>G7.5IIIa</td>
<td>NV</td>
</tr>
<tr>
<td>14514+1906</td>
<td>AB</td>
<td>2017</td>
<td>300</td>
<td>5.6</td>
<td>4.76</td>
<td>6.95</td>
<td>G8V+K5V</td>
<td>NO</td>
</tr>
<tr>
<td>17146+1423</td>
<td>AB</td>
<td>2017</td>
<td>104</td>
<td>4.8</td>
<td>3.48</td>
<td>5.4</td>
<td>M5Ib-II</td>
<td>NO</td>
</tr>
<tr>
<td>18015+2136</td>
<td></td>
<td>2017</td>
<td>256</td>
<td>6.5</td>
<td>4.85</td>
<td>5.2</td>
<td>A5IIIn</td>
<td>NV</td>
</tr>
<tr>
<td>18448+3736</td>
<td>AD</td>
<td>2017</td>
<td>150</td>
<td>43.8</td>
<td>4.34</td>
<td>5.62</td>
<td>F0IVv</td>
<td>NZ V</td>
</tr>
<tr>
<td>19307+2758</td>
<td>AB</td>
<td>2017</td>
<td>54</td>
<td>34.6</td>
<td>3.19</td>
<td>4.68</td>
<td>K3II+B9.5</td>
<td>NZ</td>
</tr>
<tr>
<td>19307+2758</td>
<td>Aa,Ac</td>
<td>2008</td>
<td>101</td>
<td>0.4</td>
<td>3.37</td>
<td>5.16</td>
<td>K3III+B0V</td>
<td>NO</td>
</tr>
<tr>
<td>20136+4644</td>
<td>Aa,Ab</td>
<td>1985</td>
<td>111</td>
<td>0.0</td>
<td>3.93</td>
<td>0.0</td>
<td>K4Ib+B3V</td>
<td>NO</td>
</tr>
<tr>
<td>20210-1447</td>
<td>AB</td>
<td>2012</td>
<td>267</td>
<td>205.4</td>
<td>3.15</td>
<td>6.08</td>
<td>F8V+A0</td>
<td>NV</td>
</tr>
<tr>
<td>20210-1447</td>
<td>Aa,Ab</td>
<td>2014</td>
<td>42</td>
<td>0.0</td>
<td>3.1</td>
<td>4.9</td>
<td>F8V+A0</td>
<td>NO</td>
</tr>
<tr>
<td>20210-1447</td>
<td>Ba,Bb</td>
<td>2015</td>
<td>59</td>
<td>0.5</td>
<td>6.16</td>
<td>9.14</td>
<td>A0III</td>
<td>NO</td>
</tr>
<tr>
<td>20467+1607</td>
<td>AB</td>
<td>2017</td>
<td>266</td>
<td>8.9</td>
<td>4.36</td>
<td>5.03</td>
<td>K1IV+F7V</td>
<td>NO Z</td>
</tr>
<tr>
<td>22292+5825</td>
<td>AC</td>
<td>2017</td>
<td>192</td>
<td>40.7</td>
<td>4.21</td>
<td>6.11</td>
<td>F5Iab+B7</td>
<td>NZ</td>
</tr>
</tbody></table>
</div>
<br />
In addition to the 8 cases where the script noted there were no doubles with information that made them 'likely' physical companions, a look at the king_wds_postv_detail.html table shows some of the remaining objects aren't great visual doubles systems either.<br />
<ul>
<li><b>gamma And:</b> For WDS 02039+4220, the likely double is components B & C, i.e. not including gamma And itself! The two B & C components are only separated by 0.2 arcseconds. As we don't all have the Hubble Space Telescope this is effectively a spectroscopic binary system and not useful visual double.</li>
<li><b>145 CMa:</b> The same problem arises for J07166-2319 (called h3945 CMa in Bob King's list), where again the likely system is components B & C, not including the bright "primary" itself.</li>
<li><b>14 Aur:</b> For WDS 05154+3241 the only likely physical system is a spectroscopic binary system of component C. So once again the "primary" is not part of a likely physical binary systsem with any of its visually close neighbors. The second component of the Ca,Cb pair is a white dwarf, which is interesting, but at 14th magnitude is far too faint to see with a small amateur scope.</li>
<li><b>31 Cyg:</b> A similar situation arises for WDS 20136+4644, where in this case it is only the primary itself that survives filtering because it too is a spectroscopic binary.</li>
</ul>
The final thing to note is the systems where the likely companion to the primary is not the closest companion: zeta Lyr A & D and delta Cep A & C.<br />
<br />
<h3>
Filtering based on negative evidence for multiplicity</h3>
In this case we accept all WDS components except those where the evidence suggests they're not related, i.e. not part of the same physical system. The script remove components with statistically different parallax and/or proper motions, or are otherwise noted in the WDS as being of dubious validity. These correspond to the WDS 'Note' column entries 'S', 'U', 'X', and 'Y'.<br />
<br />
<pre>python3 process_wds_ids.py king_processed.fits.gz king_wds_negtv_ids.html \
--wds-detail=king_wds_negtv_detail.html --filter=negative
Processing 22 targets from king_processed.fits.gz
[...output trimmed for blog...]
0 input targets with no WDS info: []
0 input targets where negative filtering removed all components: []
</pre>
<br />
This results in information overload, as too many candidate components that currently lack sufficient information to be rejected end up passing through the filter.
<br />
<div class="horizontal">
<table class="darkTable">
<thead>
<tr>
<th>WDS</th>
<th>Comp</th>
<th>Obs2</th>
<th>pa2</th>
<th>sep2</th>
<th>mag1</th>
<th>mag2</th>
<th>SpType</th>
<th>Notes</th>
</tr>
</thead>
<tbody>
<tr>
<td>00491+5749</td>
<td>AB</td>
<td>2016</td>
<td>325</td>
<td>13.4</td>
<td>3.52</td>
<td>7.36</td>
<td>G1V+M</td>
<td>NO P</td>
</tr>
<tr>
<td>00491+5749</td>
<td>BD</td>
<td>2000</td>
<td>1</td>
<td>172.2</td>
<td>7.36</td>
<td>12.8</td>
<td>K7V</td>
<td>N P</td>
</tr>
<tr>
<td>01501+2217</td>
<td></td>
<td>2016</td>
<td>165</td>
<td>2.9</td>
<td>6.33</td>
<td>7.21</td>
<td>G3III</td>
<td>N</td>
</tr>
<tr>
<td>02039+4220</td>
<td>A,BC</td>
<td>2016</td>
<td>63</td>
<td>9.4</td>
<td>2.31</td>
<td>5.02</td>
<td>K3IIb</td>
<td>N</td>
</tr>
<tr>
<td>02039+4220</td>
<td>BC</td>
<td>2010</td>
<td>96</td>
<td>0.2</td>
<td>5.3</td>
<td>6.5</td>
<td>B8V+A0V</td>
<td>NO</td>
</tr>
<tr>
<td>02124+3018</td>
<td></td>
<td>2016</td>
<td>69</td>
<td>3.7</td>
<td>5.26</td>
<td>6.67</td>
<td>G0III</td>
<td>N</td>
</tr>
<tr>
<td>02507+5554</td>
<td>AB</td>
<td>2012</td>
<td>295</td>
<td>31.4</td>
<td>3.76</td>
<td>8.5</td>
<td>M3Ib-IIa</td>
<td>N</td>
</tr>
<tr>
<td>02507+5554</td>
<td>AE</td>
<td>2012</td>
<td>297</td>
<td>242.9</td>
<td>3.76</td>
<td>9.24</td>
<td>M3Ib-IIa</td>
<td>N</td>
</tr>
<tr>
<td>02507+5554</td>
<td>CD</td>
<td>2012</td>
<td>116</td>
<td>5.1</td>
<td>11.61</td>
<td>12.7</td>
<td>OB-</td>
<td>N</td>
</tr>
<tr>
<td>02507+5554</td>
<td>CG</td>
<td>2012</td>
<td>230</td>
<td>15.3</td>
<td>11.61</td>
<td>14.0</td>
<td>OB-</td>
<td>N</td>
</tr>
<tr>
<td>03543-0257</td>
<td>AB</td>
<td>2017</td>
<td>349</td>
<td>6.9</td>
<td>4.8</td>
<td>5.89</td>
<td>G8III+A2V</td>
<td>N</td>
</tr>
<tr>
<td>03543-0257</td>
<td>AC</td>
<td>2003</td>
<td>5</td>
<td>165.9</td>
<td>4.8</td>
<td>10.5</td>
<td>G8III</td>
<td>N</td>
</tr>
<tr>
<td>05133+0252</td>
<td>AB</td>
<td>2015</td>
<td>62</td>
<td>6.9</td>
<td>4.62</td>
<td>8.5</td>
<td>K2II</td>
<td>N</td>
</tr>
<tr>
<td>05154+3241</td>
<td>AD</td>
<td>2010</td>
<td>322</td>
<td>179.7</td>
<td>5.03</td>
<td>10.75</td>
<td>A9IV</td>
<td>N</td>
</tr>
<tr>
<td>05154+3241</td>
<td>BC</td>
<td>2014</td>
<td>210</td>
<td>22.7</td>
<td>10.9</td>
<td>7.33</td>
<td>+F2V</td>
<td>N</td>
</tr>
<tr>
<td>05354-0555</td>
<td>AB</td>
<td>2012</td>
<td>141</td>
<td>11.6</td>
<td>2.77</td>
<td>7.73</td>
<td>O9III</td>
<td>N</td>
</tr>
<tr>
<td>05354-0555</td>
<td>BC</td>
<td>2014</td>
<td>94</td>
<td>40.3</td>
<td>7.73</td>
<td>9.81</td>
<td>B4</td>
<td>N</td>
</tr>
<tr>
<td>05445-2227</td>
<td>AB</td>
<td>2012</td>
<td>350</td>
<td>95.0</td>
<td>3.64</td>
<td>6.28</td>
<td>F6V+K2V</td>
<td>N</td>
</tr>
<tr>
<td>05445-2227</td>
<td>BC</td>
<td>1999</td>
<td>8</td>
<td>112.1</td>
<td>6.28</td>
<td>11.37</td>
<td>K2V</td>
<td>NL</td>
</tr>
<tr>
<td>07166-2319</td>
<td>BC</td>
<td>1999</td>
<td>165</td>
<td>999.9</td>
<td>5.84</td>
<td>6.76</td>
<td>A5m+F0</td>
<td>NV</td>
</tr>
<tr>
<td>08467+2846</td>
<td></td>
<td>2016</td>
<td>308</td>
<td>31.3</td>
<td>4.13</td>
<td>5.99</td>
<td>G7.5IIIa</td>
<td>NV</td>
</tr>
<tr>
<td>12351+1823</td>
<td></td>
<td>2016</td>
<td>272</td>
<td>20.4</td>
<td>5.11</td>
<td>6.33</td>
<td>K2III</td>
<td>N</td>
</tr>
<tr>
<td>14514+1906</td>
<td>AB</td>
<td>2017</td>
<td>300</td>
<td>5.6</td>
<td>4.76</td>
<td>6.95</td>
<td>G8V+K5V</td>
<td>NO</td>
</tr>
<tr>
<td>17146+1423</td>
<td>AB</td>
<td>2017</td>
<td>104</td>
<td>4.8</td>
<td>3.48</td>
<td>5.4</td>
<td>M5Ib-II</td>
<td>NO</td>
</tr>
<tr>
<td>18015+2136</td>
<td></td>
<td>2017</td>
<td>256</td>
<td>6.5</td>
<td>4.85</td>
<td>5.2</td>
<td>A5IIIn</td>
<td>NV</td>
</tr>
<tr>
<td>18448+3736</td>
<td>AD</td>
<td>2017</td>
<td>150</td>
<td>43.8</td>
<td>4.34</td>
<td>5.62</td>
<td>F0IVv</td>
<td>NZ V</td>
</tr>
<tr>
<td>19307+2758</td>
<td>AB</td>
<td>2017</td>
<td>54</td>
<td>34.6</td>
<td>3.19</td>
<td>4.68</td>
<td>K3II+B9.5</td>
<td>NZ</td>
</tr>
<tr>
<td>20136+4644</td>
<td>AC</td>
<td>2016</td>
<td>173</td>
<td>108.6</td>
<td>3.93</td>
<td>6.97</td>
<td>K2II</td>
<td>N</td>
</tr>
<tr>
<td>20136+4644</td>
<td>AD</td>
<td>2016</td>
<td>322</td>
<td>336.7</td>
<td>3.93</td>
<td>4.83</td>
<td>K2II</td>
<td>N</td>
</tr>
<tr>
<td>20136+4644</td>
<td>CH</td>
<td>2014</td>
<td>62</td>
<td>60.6</td>
<td>6.97</td>
<td>12.6</td>
<td>B5V</td>
<td>N</td>
</tr>
<tr>
<td>20136+4644</td>
<td>CI</td>
<td>2015</td>
<td>136</td>
<td>60.2</td>
<td>6.97</td>
<td>12.26</td>
<td>B5V</td>
<td>N</td>
</tr>
<tr>
<td>20136+4644</td>
<td>DC</td>
<td>2003</td>
<td>150</td>
<td>431.8</td>
<td>4.83</td>
<td>6.97</td>
<td>A5IIIn</td>
<td>N</td>
</tr>
<tr>
<td>20136+4644</td>
<td>FJ</td>
<td>2015</td>
<td>217</td>
<td>4.2</td>
<td>13.9</td>
<td>15.1</td>
<td></td>
<td>N R</td>
</tr>
<tr>
<td>20136+4644</td>
<td>HK</td>
<td>2015</td>
<td>262</td>
<td>8.9</td>
<td>11.74</td>
<td>10.87</td>
<td></td>
<td>N K</td>
</tr>
<tr>
<td>20210-1447</td>
<td>AB</td>
<td>2012</td>
<td>267</td>
<td>205.4</td>
<td>3.15</td>
<td>6.08</td>
<td>F8V+A0</td>
<td>NV</td>
</tr>
<tr>
<td>20210-1447</td>
<td>AC</td>
<td>2012</td>
<td>133</td>
<td>226.1</td>
<td>3.15</td>
<td>8.83</td>
<td>F8V+A0</td>
<td>N</td>
</tr>
<tr>
<td>20210-1447</td>
<td>BC</td>
<td>2000</td>
<td>111</td>
<td>396.7</td>
<td>6.08</td>
<td>8.83</td>
<td>A0III</td>
<td>N</td>
</tr>
<tr>
<td>20210-1447</td>
<td>DE</td>
<td>2000</td>
<td>321</td>
<td>3.9</td>
<td>13.7</td>
<td>14.4</td>
<td></td>
<td>N</td>
</tr>
<tr>
<td>20467+1607</td>
<td>AB</td>
<td>2017</td>
<td>266</td>
<td>8.9</td>
<td>4.36</td>
<td>5.03</td>
<td>K1IV+F7V</td>
<td>NO Z</td>
</tr>
<tr>
<td>22292+5825</td>
<td>AC</td>
<td>2017</td>
<td>192</td>
<td>40.7</td>
<td>4.21</td>
<td>6.11</td>
<td>F5Iab+B7</td>
<td>NZ</td>
</tr>
<tr>
<td>22292+5825</td>
<td>DE</td>
<td>2008</td>
<td>23</td>
<td>1.4</td>
<td>13.9</td>
<td>14.0</td>
<td></td>
<td>N</td>
</tr>
</tbody></table>
</div>
<br />
I've included the table for completeness, although I can't recommend using this form of filtering. A lot of faint components with large angular separations are listed, which simply aren't interesting from an amateur astronomical point-of-view.
<br />
<h3>
What next?</h3>
This post is already very long and much delayed, so I'll put off the next stage of the process until Part 3. In that post we'll take our improved list of stars that includes the primary and likely companion IDs ("king_wds_postv_ids.html" above) and run that through the script from Part 1 that queries Simbad to get the observable properties: positions, magnitudes, parallaxes, proper motions, effective temperatures and spectral types for the stars. Once we have the observables we'll finally be ready to calculate the derived properties we're interested in: distance, luminosity, radius, and rough stellar masses.
<br />
<h3>
Acknowledgements:</h3>
This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-19348428119094594612018-03-21T10:32:00.001-04:002018-04-29T17:19:38.743-04:00Colorful binary star systems for small telescopes: Part 1I recently got a small telescope (a <a href="https://www.celestron.com/products/nexstar-6se-computerized-telescope" target="_blank">Celestron NexStar 6SE</a>) in order to introduce the kids to the wonders of the sky, albeit somewhat dulled by suburban light pollution.<br />
<br />
While waiting for the weather to become warm enough to actually use it I've been pondering what interesting objects can actually be seen given the constraints of the hardware. Randomly looking at things without knowing what they are can only get you so far, especially with kids.<br />
<br />
One class of (non-Solar-system) object that can be visually impressive are visual double stars with a significant difference in color. Differences in color are easy for kids to understand as differences in temperature, which leads on to understanding there are different types of stars...<br />
<br />
That thought lead me to this nice article,<a href="http://www.skyandtelescope.com/observing/colored-double-stars-real-and-imagined/" target="_blank">"Colored Double Stars, Real and Imagined" by Bob King, Sky & Telescope, December 14 2016</a>. Its a good article, with images, information and even an HTML table of the objects, rough coordinates, magnitude and spectral types. I've reproduced the table below:<br />
<br />
<div class="horizontal">
<table class="darkTable">
<thead>
<tr>
<th>Star</th>
<th>R.A.</th>
<th>Dec.</th>
<th>Mag A</th>
<th>Mag B</th>
<th>Sep.</th>
<th>P.A.</th>
<th>Color difference</th>
<th>Spec. Class</th>
</tr>
</thead>
<tbody>
<tr>
<td>η Cas</td>
<td>00h 49m</td>
<td>+57° 49'</td>
<td>3.5</td>
<td>7.2</td>
<td>13"</td>
<td>317°</td>
<td>1.7</td>
<td>G0, K7</td>
</tr>
<tr>
<td>1 Ari</td>
<td>01h 50m</td>
<td>+22° 16'</td>
<td>5.9</td>
<td>7.2</td>
<td>2.9"</td>
<td>164°</td>
<td>3.5</td>
<td>K1, A6</td>
</tr>
<tr>
<td>γ And</td>
<td>02h 04m</td>
<td>+42° 20'</td>
<td>2.1</td>
<td>4.8</td>
<td>9.8"</td>
<td>64°</td>
<td>3.5</td>
<td>K3, B8</td>
</tr>
<tr>
<td>ι Tri = 6 Tri</td>
<td>02h 12m</td>
<td>+30° 18'</td>
<td>5.3</td>
<td>6.7</td>
<td>4"</td>
<td>69°</td>
<td>1.0</td>
<td>G5, F5</td>
</tr>
<tr>
<td>η Per</td>
<td>02h 51m</td>
<td>+55° 54'</td>
<td>3.8</td>
<td>8.5</td>
<td>28"</td>
<td>301°</td>
<td>3.0</td>
<td>K3, A3</td>
</tr>
<tr>
<td>32 Eri</td>
<td>03h 54m</td>
<td>–02° 57'</td>
<td>4.8</td>
<td>5.9</td>
<td>7"</td>
<td>254°</td>
<td>2.6</td>
<td>G8, A2</td>
</tr>
<tr>
<td>ρ Ori</td>
<td>05h 13m</td>
<td>+02° 52'</td>
<td>4.6</td>
<td>8.5</td>
<td>7"</td>
<td>64°</td>
<td>1.7</td>
<td>K3, F7</td>
</tr>
<tr>
<td>14 Aur</td>
<td>05h 15m</td>
<td>+32° 41'</td>
<td>5.0</td>
<td>7.4</td>
<td>15"</td>
<td>226°</td>
<td>0.4</td>
<td>A9, F3</td>
</tr>
<tr>
<td>ι Ori</td>
<td>05h 35m</td>
<td>+05° 57'</td>
<td>2.9</td>
<td>7.0</td>
<td>10.9"</td>
<td>142°</td>
<td>0.2</td>
<td>O9, B1</td>
</tr>
<tr>
<td>γ Lep</td>
<td>05h 44m</td>
<td>–22° 27'</td>
<td>3.6</td>
<td>6.3</td>
<td>97"</td>
<td>350°</td>
<td>1.6</td>
<td>F6, K2</td>
</tr>
<tr>
<td>h3945 CMa</td>
<td>07h 17m</td>
<td>–23° 19'</td>
<td>5.0</td>
<td>5.8</td>
<td>26.8"</td>
<td>52°</td>
<td>2.0</td>
<td>K0, F0</td>
</tr>
<tr>
<td>ι Cnc</td>
<td>08h 47m</td>
<td>+28° 46'</td>
<td>4.0</td>
<td>6.6</td>
<td>30.6"</td>
<td>307°</td>
<td>2.6</td>
<td>G8, A2</td>
</tr>
<tr>
<td>24 Com</td>
<td>12h 35m</td>
<td>+18° 23'</td>
<td>5.1</td>
<td>6.3</td>
<td>20"</td>
<td>270°</td>
<td>2.2</td>
<td>K0, A9</td>
</tr>
<tr>
<td>ξ Boo</td>
<td>14h 51m</td>
<td>+19° 06'</td>
<td>4.8</td>
<td>7.0</td>
<td>6"</td>
<td>343°</td>
<td>0.5</td>
<td>G8, K4</td>
</tr>
<tr>
<td>α Her</td>
<td>17h 15m</td>
<td>+14° 23'</td>
<td>3.1</td>
<td>5.4</td>
<td>5"</td>
<td>106°</td>
<td>1.7</td>
<td>M5, G8</td>
</tr>
<tr>
<td>95 Her</td>
<td>18h 02m</td>
<td>+21° 36'</td>
<td>4.9</td>
<td>5.2</td>
<td>6"</td>
<td>258°</td>
<td>2.3</td>
<td>A5, G8</td>
</tr>
<tr>
<td>ζ Lyr</td>
<td>18h 45m</td>
<td>+37° 36'</td>
<td>4.3</td>
<td>5.6</td>
<td>44"</td>
<td>150°</td>
<td>1.1</td>
<td>B7, A8</td>
</tr>
<tr>
<td>Albireo</td>
<td>19h 31m</td>
<td>+27° 57'</td>
<td>3.4</td>
<td>4.7</td>
<td>35"</td>
<td>54°</td>
<td>3.5</td>
<td>K3, B8</td>
</tr>
<tr>
<td>31 Cyg</td>
<td>20h 14m</td>
<td>+46° 44'</td>
<td>3.8</td>
<td>4.8</td>
<td>107"</td>
<td>325°</td>
<td>2.9</td>
<td>K2, B3</td>
</tr>
<tr>
<td>β Cap</td>
<td>20h 21m</td>
<td>–14° 47'</td>
<td>3.2</td>
<td>6.1</td>
<td>207"</td>
<td>267°</td>
<td>3.2</td>
<td>K0, B8</td>
</tr>
<tr>
<td>γ Del</td>
<td>20h 47m</td>
<td>+16° 07'</td>
<td>4.4</td>
<td>5.0</td>
<td>9"</td>
<td>267°</td>
<td>1.4</td>
<td>K1, F7</td>
</tr>
<tr>
<td>δ Cep</td>
<td>22h 29m</td>
<td>+58° 25'</td>
<td>4.1</td>
<td>6.3</td>
<td>40.9"</td>
<td>191°</td>
<td>2.5</td>
<td>G2, B7</td>
</tr>
</tbody></table>
</div>
<br />
But it and the article still leave me with many questions I'd like to know answers for *before* actually trying to observe these systems and show them to my kids:<br />
<ul>
<li>How far away are these stars?</li>
<li>What type of star are they? (main sequence dwarfs? Giants?)</li>
<li>What is their true luminosity, mass, radius, and temperature compared to the Sun?</li>
<li>How long do stars like these live?</li>
<li>How far apart physically are these stars?</li>
<li>Are they actually a binary (or multiple) star systems, or just chance alignments?</li>
</ul>
In addition to these questions, there are some issues with the list as presented that make it hard to use it.<br />
<ul>
<li>What are the names/identifiers of the companion stars? The names given above are presumably the Primary, i.e. visually brightest, member of the pair. But what are the other member or members of the system?</li>
<li>What are the true coordinates of the objects? The RA/Decs given above are rounded to the nearest minute and arc-minute. One minute in RA is 15 arcminutes, or half the angular diameter of the moon. The number of objects in a professional astronomical catalog within a 15 arcminute radius is likely pretty large.</li>
<li>The Celestron recognizes SAO star identifiers, so what are those for the objects given above?</li>
</ul>
<ul>
</ul>
As I used to be a professional astronomer I know answers to all these questions either already exist, or can be determined to some level of accuracy for such bright (and hence nearby) stars and accessed via <a href="http://simbad.u-strasbg.fr/simbad/" target="_blank">SIMBAD</a> (<a href="https://en.wikipedia.org/wiki/SIMBAD" target="_blank">wikipedia entry here</a>). Its just a matter of collating the right information from different astronomers and applying some scientific criteria to choose between multiple, quite possibly contradictory, sources of information. I started trying to collate that information, but after spending quite some time getting only the basic beginnings of what I needed I discovered I'd somehow missed a bunch of the stars listed in Bob King's table and hence wasn't even close to being finished. Argh!<br />
<br />
There had to be a better, more automated, way of getting the information. So I set out to write one, of which <a href="https://github.com/DaveStrickland/DoubleStars" target="_blank">the DoubleStars github project</a> is the first installment. The table shown below is one of the outputs of star_query.py after processing the HTML table from Bob King's article (above), more information than shown is written to an additional gzipped fits-format table.<br />
<br />
For each input target the table below shows the official SIMBAD identifier, along with additional identifiers recognized by Simbad. In particular the <a href="http://ad.usno.navy.mil/wds/" target="_blank">Washington Double Star</a> ID (to investigate the true status of the visual double as a binary system), the SAO ID (for controlling the NexStar), and the <a href="https://en.wikipedia.org/wiki/Hipparcos" target="_blank">Hipparcos</a> Output Catalog (HIP, for parallax and hence true distance). The <a href="https://en.wikipedia.org/wiki/Henry_Draper_Catalogue" target="_blank">Henry Draper (HD)</a> ID is useful when searching in Kstars (which can also be used to control the NexStar). In addition, more accurate RA and Dec, spectral types with luminosity class, and in some cases stellar effective temperature (in Kelvin) and metal abundance are given (presumably again for the Primary).<br />
<br />
<div class="horizontal">
<table class="darkTable">
<thead>
<tr>
<th>Star</th>
<th>SimbadID</th>
<th>WDS</th>
<th>SAO</th>
<th>HIP</th>
<th>NAME</th>
<th>HD</th>
<th>RA_icrs</th>
<th>DEC_icrs</th>
<th>magV</th>
<th>spec_type</th>
<th>Teff_(Fe_H)</th>
<th>[Fe/H]</th>
</tr>
</thead>
<tbody>
<tr>
<td>eta Cas</td>
<td>* eta Cas</td>
<td>J00491+5749AB</td>
<td>21732</td>
<td>3821</td>
<td>Achird</td>
<td>4614</td>
<td>0:49:06.3</td>
<td>57:48:54.7</td>
<td>3.44</td>
<td>F9V+M0-V</td>
<td>5899</td>
<td>-0.31</td>
</tr>
<tr>
<td>1 Ari</td>
<td>* 1 Ari</td>
<td>J01501+2217AB</td>
<td>74966</td>
<td>8544</td>
<td>None</td>
<td>None</td>
<td>1:50:08.6</td>
<td>22:16:31.2</td>
<td>5.86</td>
<td>G3III+A3IV</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>gamma And</td>
<td>* gam And</td>
<td>J02039+4220A,BC</td>
<td>None</td>
<td>9640</td>
<td>Almach</td>
<td>None</td>
<td>2:03:54.0</td>
<td>42:19:47.0</td>
<td>2.10</td>
<td>K3II+B9.5V+A0V</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>iota Tri = 6 Tri</td>
<td>* iot Tri</td>
<td>J02124+3018AB</td>
<td>55347</td>
<td>10280</td>
<td>None</td>
<td>13480</td>
<td>2:12:22.3</td>
<td>30:18:11.0</td>
<td>4.95</td>
<td>G0III+G5III</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>eta Per</td>
<td>* eta Per</td>
<td>J02507+5554A</td>
<td>23655</td>
<td>13268</td>
<td>Miram</td>
<td>17506</td>
<td>2:50:41.8</td>
<td>55:53:43.8</td>
<td>3.79</td>
<td>K3-Ib-IIa</td>
<td>3500</td>
<td>0.09</td>
</tr>
<tr>
<td>32 Eri</td>
<td>* 32 Eri</td>
<td>J03543-0257AB</td>
<td>None</td>
<td>18255</td>
<td>None</td>
<td>None</td>
<td>3:54:17.5</td>
<td>-2:57:17.0</td>
<td>4.45</td>
<td>G8III+A1V</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>rho Ori</td>
<td>* rho Ori</td>
<td>J05133+0252AB</td>
<td>112528</td>
<td>24331</td>
<td>None</td>
<td>33856</td>
<td>5:13:17.5</td>
<td>2:51:40.5</td>
<td>4.44</td>
<td>K1III</td>
<td>4599</td>
<td>0.22</td>
</tr>
<tr>
<td>14 Aur</td>
<td>* 14 Aur</td>
<td>J05154+3241A</td>
<td>57799</td>
<td>24504</td>
<td>None</td>
<td>33959</td>
<td>5:15:24.4</td>
<td>32:41:15.4</td>
<td>5.00</td>
<td>A9V</td>
<td>7670</td>
<td>0.00</td>
</tr>
<tr>
<td>iota Ori</td>
<td>* iot Ori</td>
<td>J05354-0555A</td>
<td>132323</td>
<td>26241</td>
<td>Hatysa</td>
<td>37043</td>
<td>5:35:26.0</td>
<td>-5:54:35.6</td>
<td>2.77</td>
<td>O9IIIvar</td>
<td>18000</td>
<td>0.10</td>
</tr>
<tr>
<td>gamma Lep</td>
<td>* gam Lep</td>
<td>J05445-2227A</td>
<td>170759</td>
<td>27072</td>
<td>None</td>
<td>38393</td>
<td>5:44:27.8</td>
<td>-22:26:54.2</td>
<td>3.60</td>
<td>F6V</td>
<td>6306</td>
<td>-0.12</td>
</tr>
<tr>
<td>h3945 CMa</td>
<td>* 145 CMa</td>
<td>J07166-2319A</td>
<td>173349</td>
<td>35210</td>
<td>None</td>
<td>56577</td>
<td>7:16:36.8</td>
<td>-23:18:56.1</td>
<td>4.79</td>
<td>K3Ib-</td>
<td>3970</td>
<td>0.03</td>
</tr>
<tr>
<td>iota Cnc</td>
<td>* iot Cnc</td>
<td>J08467+2846A</td>
<td>80416</td>
<td>43103</td>
<td>None</td>
<td>74739</td>
<td>8:46:41.8</td>
<td>28:45:35.6</td>
<td>4.02</td>
<td>G8IIIaBa0.2</td>
<td>4905</td>
<td>-0.06</td>
</tr>
<tr>
<td>24 Com</td>
<td>* 24 Com A</td>
<td>J12351+1823A</td>
<td>100160</td>
<td>61418</td>
<td>None</td>
<td>109511</td>
<td>12:35:07.8</td>
<td>18:22:37.4</td>
<td>5.02</td>
<td>K0II-III</td>
<td>0</td>
<td>-0.04</td>
</tr>
<tr>
<td>xi Boo</td>
<td>* ksi Boo</td>
<td>J14514+1906AB</td>
<td>101250</td>
<td>72659</td>
<td>None</td>
<td>131156</td>
<td>14:51:23.4</td>
<td>19:06:01.7</td>
<td>4.59</td>
<td>G7Ve+K5Ve</td>
<td>5410</td>
<td>-0.05</td>
</tr>
<tr>
<td>alpha Her</td>
<td>* alf Her</td>
<td>J17146+1423AB</td>
<td>None</td>
<td>84345</td>
<td>Rasalgethi</td>
<td>156014J</td>
<td>17:14:38.9</td>
<td>14:23:25.2</td>
<td>3.06</td>
<td>M5Ib-II+G5III+F2</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>95 Her</td>
<td>* 95 Her</td>
<td>J18015+2136AB</td>
<td>85648</td>
<td>88267</td>
<td>None</td>
<td>164669</td>
<td>18:01:30.4</td>
<td>21:35:44.8</td>
<td>0.00</td>
<td>A5IIIn</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>zeta Lyr</td>
<td>* zet01 Lyr</td>
<td>J18448+3736A</td>
<td>67321</td>
<td>91971</td>
<td>None</td>
<td>173648</td>
<td>18:44:46.4</td>
<td>37:36:18.4</td>
<td>4.36</td>
<td>Am</td>
<td>7914</td>
<td>0.38</td>
</tr>
<tr>
<td>Albireo</td>
<td>* bet Cyg A</td>
<td>J19307+2758A</td>
<td>87301</td>
<td>95947</td>
<td>Albereo</td>
<td>None</td>
<td>19:30:43.3</td>
<td>27:57:34.8</td>
<td>3.09</td>
<td>K3II+B9.5V</td>
<td>4270</td>
<td>-0.17</td>
</tr>
<tr>
<td>31 Cyg</td>
<td>* omi01 Cyg</td>
<td>J20136+4644Aa,Ab</td>
<td>49337</td>
<td>99675</td>
<td>None</td>
<td>192577</td>
<td>20:13:37.9</td>
<td>46:44:28.8</td>
<td>3.80</td>
<td>K3Ib+B2IV-V</td>
<td>4186</td>
<td>0.03</td>
</tr>
<tr>
<td>beta Cap</td>
<td>* bet Cap</td>
<td>J20210-1447AB</td>
<td>None</td>
<td>None</td>
<td>Dabih</td>
<td>None</td>
<td>20:21:00.7</td>
<td>-14:46:53.0</td>
<td>0.00</td>
<td></td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>gamma Del</td>
<td>* gam Del</td>
<td>J20467+1607AB</td>
<td>None</td>
<td>None</td>
<td>None</td>
<td>None</td>
<td>20:46:39.2</td>
<td>16:07:27.0</td>
<td>3.91</td>
<td>F7</td>
<td>0</td>
<td>0.00</td>
</tr>
<tr>
<td>delta Cep</td>
<td>* del Cep</td>
<td>J22292+5825A</td>
<td>34508</td>
<td>110991</td>
<td>None</td>
<td>213306</td>
<td>22:29:10.3</td>
<td>58:24:54.7</td>
<td>3.75</td>
<td>F5Iab:+B7-8</td>
<td>5695</td>
<td>7.62</td>
</tr>
</tbody></table>
</div>
<br />
That is a decent start, but it does have some deficiencies. In some cases the identifier is clearly associated with a pair of objects, as can be seen from the multiple spectral types, e.g. gamma And, iota Tri, 31 Cyg. That is not quite what we want, as the positions and other data aren't for a single star. Solving that is a topic for another post...Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-46858588888711158182018-02-04T14:51:00.000-05:002018-02-04T14:51:40.170-05:00Fixing Windows Update problemsI've been experiencing some Windows Update problems, in particular Windows update endlessly "Checking for updates". After much trial and error I found a <a href="https://www.howtogeek.com/247380/how-to-fix-windows-update-when-it-gets-stuck/">How-To Geek article by Walter Glenn</a> helpful. In particular, installing and using the <a href="http://download.wsusoffline.net/">WSUS Offline Update</a> was necessary before cleaning out the wuauserv cache.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-38084303852821109562018-02-01T21:41:00.000-05:002018-02-01T21:41:10.798-05:00Reading large JP2 files on FedoraI recently had to analyze some very large (>100 megapixel) JP2 files and ran into the following problem on my Fedora 27 machine:<br />
<style type="text/css">
pre.CICodeFormatter{
font-family:arial;
font-size:12px;
border:1px dashed #CCCCCC;
width:99%;
height:auto;
overflow:auto;
background:#f0f0f0;
line-height:20px;
padding:0px;
color:#000000;
text-align:left;
}
pre.CICodeFormatter code{
color:#000000;
word-wrap:normal;
}
</style>
<pre class="CICodeFormatter"><code class="CICodeFormatter"> jiv sat16_abi_fd6_l1b_CTfullimage_BA03_2018-030-204905.jp2
maximum number of samples exceeded (117679104 &gt; 67108864)
error: cannot decode code stream
error: cannot load image data
cannot load image
Segmentation fault (core dumped)
</code></pre>
<br />
I got the same error "maximum number of samples exceeded" message from octave's imread or using gimp, which lead me to this <a href="https://github.com/mdadams/jasper/issues/137">link pointing to a compiled in limit in libjasper</a>.<br />
<br />
The solution is to compile a custom version of libjasper with a larger limit. This is straightforward, but how to get it done cleanly in terms of RPMs?<br />
<style type="text/css">
pre.CICodeFormatter{
font-family:arial;
font-size:12px;
border:1px dashed #CCCCCC;
width:99%;
height:auto;
overflow:auto;
background:#f0f0f0;
line-height:20px;
padding:0px;
color:#000000;
text-align:left;
}
pre.CICodeFormatter code{
color:#000000;
word-wrap:normal;
}
</style>
<br />
<pre class="CICodeFormatter"><code class="CICodeFormatter">1: sudo dnf -y install rpm-build rpmdevtools
2: rpmdev-setuptree
3: rpm -ivh jasper-2.0.14-1.fc27.src.rpm
4: cd rpmbuild/BUILD
5: tar xzvf ../SOURCES/jasper-2.0.14.tar.gz
6: cp -R jasper-2.0.14 jasper-2.0.14p
7: geany ./jasper-2.0.14p/jasper-2.0.14/builder/src/libjasper/include/jasper/jas_config.h
8: diff -puNr jasper-2.0.14/ jasper-2.0.14p/ > ../SOURCES/jasper-2.0.14-largefile.patch
9: cd ../SPECS
10: geany jasper.spec
11: QA_RPATHS=$(( 0x0001|0x0010 )) rpmbuild -ba jasper.spec
12: ls ../RPMS/x86_64/
</code></pre>
<br />
For step #7 we're making a single line change to move from a 64 megapixel limit to something closer to what we want, in my case 512 megapixels. Here is the diff generated in step #8: <br />
<style type="text/css">
pre.CICodeFormatter{
font-family:arial;
font-size:12px;
border:1px dashed #CCCCCC;
width:99%;
height:auto;
overflow:auto;
background:#f0f0f0;
line-height:20px;
padding:0px;
color:#000000;
text-align:left;
}
pre.CICodeFormatter code{
color:#000000;
word-wrap:normal;
}
</style>
<br />
<pre class="CICodeFormatter"><code class="CICodeFormatter">1: diff -puNr jasper-2.0.14/src/libjasper/include/jasper/jas_config.h.in jasper-2.0.14p/src/libjasper/include/jasper/jas_config.h.in
2: --- jasper-2.0.14/src/libjasper/include/jasper/jas_config.h.in 2017-09-14 19:20:10.000000000 -0400
3: +++ jasper-2.0.14p/src/libjasper/include/jasper/jas_config.h.in 2018-02-01 11:27:13.784393051 -0500
4: @@ -61,7 +61,7 @@
5: #endif
6: #if !defined(JAS_DEC_DEFAULT_MAX_SAMPLES)
7: -#define JAS_DEC_DEFAULT_MAX_SAMPLES (64 * ((size_t) 1048576))
8: +#define JAS_DEC_DEFAULT_MAX_SAMPLES (512 * ((size_t) 1048576))
9: #endif
10: #if defined(__GNUC__) && !defined(__clang__)
</code></pre>
<br />
A number of changes need to be made to the spec file in step #10. I changed the release to something that lets me know I made this,
switched off debug builds (as they seem to cause trouble), and added the
patch.Only the added lines are shown below. <br />
<style type="text/css">
pre.CICodeFormatter{
font-family:arial;
font-size:12px;
border:1px dashed #CCCCCC;
width:99%;
height:auto;
overflow:auto;
background:#f0f0f0;
line-height:20px;
padding:0px;
color:#000000;
text-align:left;
}
pre.CICodeFormatter code{
color:#000000;
word-wrap:normal;
}
</style>
<br />
<pre class="CICodeFormatter"><code class="CICodeFormatter"> Release: 2dks%{?dist}
...
%global debug_package %{nil}
...
Patch102: jasper-2.0.14-largefile.patch
...
%if "%{_arch}" == "x86_64"
%patch102 -p1 -b .largefile
%endif
</code></pre>
<br />
Once the RPMs are built (step #11) as user you can install them as root. <br />
<style type="text/css">
pre.CICodeFormatter{
font-family:arial;
font-size:12px;
border:1px dashed #CCCCCC;
width:99%;
height:auto;
overflow:auto;
background:#f0f0f0;
line-height:20px;
background-image:URL(http://2.bp.blogspot.com/_z5ltvMQPaa8/SjJXr_U2YBI/AAAAAAAAAAM/46OqEP32CJ8/s320/codebg.gif);
padding:0px;
color:#000000;
text-align:left;
}
pre.CICodeFormatter code{
color:#000000;
word-wrap:normal;
}
</style>
<br />
<pre class="CICodeFormatter"><code class="CICodeFormatter">1: su - # enter password
2: cd ~<username>/rpmbuild/RPMS/x86_64/
3: dnf install `ls | grep -v debug | xargs`
4: # if you need to go back to the old system versions use
5: # dnf downgrade jasper jasper-devel jasper-libs jasper-utils
</code></pre>
<br />
Then check that you can load your large JP2 file without that error message. If not, its likely you made a mistake in modifying the .h file, creating the patch or the spec file. (I had to try this a few times before I got it right.)<br />
<br />
You can lock down these rpms so that dnf upgrades wont replace your hard work using <a href="https://www.perl.com/article/prevent-harmful-updates-with-versionlock/">dnf versionlock, see e.g., here</a>.<br />
<br />
Some useful links on dealing with source rpms on Fedora/Redhat systems:<br />
<ul>
<li><a href="https://ask.fedoraproject.org/en/question/87205/how-do-i-install-a-src-rpm-with-dnf/">How to install a source rpm with dnf</a>. </li>
<li><a href="http://bradthemad.org/tech/notes/patching_rpms.php">Patching rpms</a> on Brad the Mad's blog.</li>
</ul>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-16511817153218975042016-12-28T18:00:00.000-05:002016-12-28T18:00:25.012-05:00Cloning a VirtualBox VM to an external drive under Windows 7If you want to create a clone of a VirtualBox VM where the clone will be on an external drive, this can be done without performing any additional copying.<br />
<ol>
<li>Ensure the external drive you wish to use is mounted, you have enough disk space for the clone, and that you have an easy to find directory to store your clones(s) in. For example, I have W:\VirtualBoxVMs\</li>
<li>Shutdown the VM to be cloned.</li>
<li>In the VM VirtualBox Manager application, click File -> Preferences, and select the General tab.</li>
<li>Make a note of the current Default Machine Folder that your VMs are in, e.g. C:\Users\YourUserName\VirtualBox VMs\</li>
<li>Change the Default Machine Folder from the current one to the external directory you want the clone to be placed in. (In this example, W:\VirtualBoxVMs\).</li>
<li>Right click the VM you wish to clone and select "Clone"</li>
<li>When prompted for Clone Type select "Full clone" and click the Clone button</li>
<li> Cloning will take a while, so do something else...</li>
<li>When the cloning is finished, verify that the clone boots and runs correctly by starting it from the VirtaulBox VM Manager.</li>
<li>Shut down the clone.</li>
<li>Perform steps 3 and 5 again, setting the Default Machine Folder back to the original value you made a note of in step 4.</li>
<li>You can now safely remove the external drive if you want. (The clone will be marked as inaccessible if you dismount the drive, but will be automatically re-detected when the drive is mounted again in the future.) </li>
</ol>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-43894977298535741332016-07-08T06:25:00.000-04:002016-07-08T06:25:22.680-04:00Changing PDF paper typesUseful to know: use pdfinfo to find metadata and paper size, pdfjam to change the paper type/size specified in a PDF file.<br />
<br />
<pre style="background: #f0f0f0; border: 1px dashed #cccccc; color: black; font-family: "arial"; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"><code style="color: black; word-wrap: normal;"> pdfjam --outfile out.pdf --paper letter original_a4.pdf
</code></pre>
<br />
As seen in Unix & Linux Stack Exchange <a href="http://unix.stackexchange.com/questions/185145/convert-pdf-to-a-different-page-size-us-letter-a4">http://unix.stackexchange.com/questions/185145/convert-pdf-to-a-different-page-size-us-letter-a4</a><br />
<br />
[Source code formatting from <a href="http://codeformatter.blogspot.com/">http://codeformatter.blogspot.com/</a>] Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-25040057962957896942016-05-17T11:23:00.001-04:002016-05-17T11:23:06.921-04:00Backing up virtual machines and fat32<div xmlns='http://www.w3.org/1999/xhtml'>Couldn't backup a 100GB virtual machine image to a truecrypt encrypted external drive because the drive was formatted Fat32. Turned out you can convert it to NTFS while mounted without losing data:<br/>
Accessories > right click on Command prompt<br/>
>convert x: /fs:ntfs<br/>
<br/>
After that a normal copy to the external drive worked fine. No data loss!</div>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-19222476508635596982016-03-30T09:36:00.001-04:002016-03-30T09:36:41.048-04:00Testing... Testing...<div xmlns='http://www.w3.org/1999/xhtml'>This is a <b>test</b> with a link to [NASA HTTP://www.NASA.gov].</div>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-50040785910037599152015-09-03T21:52:00.000-04:002015-09-03T21:52:00.852-04:00Astronomy routines for MATLAB (and Octave?)Over the last few years I've become a big fan of Matlab and its free, open-source, twin Octave so I was pleased to discover at least some professional Astronomers use it. The <a href="http://webhome.weizmann.ac.il/home/eofek/matlab/">Astronomy & Astrophysics package for Matlab</a> (<a href="http://adsabs.harvard.edu/abs/2014ascl.soft07005O">Ofek 2014</a>, see also <a href="http://ascl.net/1407.005">http://ascl.net/1407.005</a>) contains just under a thousand Matlab functions, including catalog access and ds9-interaction. <br />
<br />
Hat tip: The <a href="http://ascl.net/">Astrophysics Source Code Library</a>.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-67551068181533897352015-07-13T07:28:00.000-04:002015-07-13T10:28:26.266-04:00Only a million miles to Pluto & Charon<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-zHD6TXf5_44/VaPJb94pp4I/AAAAAAAADHk/13kGHtWSEJQ/s1600/pluto_charon_150709_color_final.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="" border="0" height="187" src="http://1.bp.blogspot.com/-zHD6TXf5_44/VaPJb94pp4I/AAAAAAAADHk/13kGHtWSEJQ/s640/pluto_charon_150709_color_final.png" title="Pluto and Charon" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">True color image of Charon (left) and Plut (right), taken July 09 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute</td></tr>
</tbody></table>
In just over 21 hours, at 11:49:57 UTC on Tuesday 14th of July 2015, New Horizons will at it closet to Pluto. New Horizons is still roughly 1.1 million miles away from the point of closest approach but its moving at 13.8 kilometers per second with respect to Pluto (That is 14.5 km/s with respect to the Sun, or ~31,000 mph and 32,400 mph respectively).<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-nrvw1tVka7c/VaPJ0FGgL_I/AAAAAAAADHs/xvHBQDivF20/s1600/Pluto%2BAnnotated%2B7-12-15.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="360" src="http://3.bp.blogspot.com/-nrvw1tVka7c/VaPJ0FGgL_I/AAAAAAAADHs/xvHBQDivF20/s640/Pluto%2BAnnotated%2B7-12-15.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Surface features on Pluto. July 12 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute</td></tr>
</tbody></table>
<br />
But already the views of Pluto and Charon are amazing, all the more so because they're just so different.<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-CRMit2eOhP0/VaPKT5zKG5I/AAAAAAAADH0/ebNmhCPr81Y/s1600/Charon%2BAnnotated%2B7-12-15.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="360" src="http://1.bp.blogspot.com/-CRMit2eOhP0/VaPKT5zKG5I/AAAAAAAADH0/ebNmhCPr81Y/s640/Charon%2BAnnotated%2B7-12-15.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Surface features on Charon. July 12 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute</td></tr>
</tbody></table>
For the latest from New Horizons, visit their JHU/APL webpage: <a href="http://pluto.jhuapl.edu/index.php">http://pluto.jhuapl.edu/index.php</a>Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-77577830388405834232015-07-09T07:50:00.000-04:002015-07-09T08:53:01.232-04:00Blobs in Space!Interesting times, but not much time to comment on them.<br />
<br />
The Sun is doing it's thing as always. Not much too special to talk about today.
For more data go to <a href="http://sdo.gsfc.nasa.gov/data/">http://sdo.gsfc.nasa.gov/data/<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://sdo.gsfc.nasa.gov/assets/img/latest/f_211_193_171_512.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://sdo.gsfc.nasa.gov/assets/img/latest/f_211_193_171_512.jpg" height="320" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"> AIA 211 Angstrom band is red, AIA 193 Angstrom band is green, and AIA 171 is blue</td></tr>
</tbody></table>
</a><br />
<br />
In our back yard the robotic missions to Minor Planets Ceres and Pluto are really getting interesting.<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.jpl.nasa.gov/spaceimages/images/largesize/PIA18925_hires.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://www.jpl.nasa.gov/spaceimages/images/largesize/PIA18925_hires.jpg" height="112" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Dwarf planet Ceres as seen by NASA's DAWN mission</td></tr>
</tbody></table>
<a href="http://www.nasa.gov/mission_pages/dawn/main/index.html">NASA's DAWN mission to Ceres</a> is continuing its second mapping orbit. <a href="http://dawn.jpl.nasa.gov/multimedia//images/ceres.html">The CERES Image Of The Day</a> website is worth looking at every now and again. The image on the right was taken on Feb. 19, 2015 from a distance of nearly 29,000 miles (46,000 kilometers) from Ceres.<br />
<br />
Fun Ceres facts: It is about 590 miles across, and accounts for about 25% of the entire asteroid belt's mass. Yet it is less than 1/14th of the mass of Plute, the other dwarf planet of note at the moment.<br />
<br />
It is amazing to finally see non-deconvolved images of Pluto that actually look like something other than a blurry blob. [Read more at <a href="http://www.space.com/29818-pluto-charon-new-horizons-photo.html">Space.com</a>] Original images from <a href="http://pluto.jhuapl.edu/soc/Pluto-Encounter/view_obs.php?image=data/pluto/level2/lor/jpeg/029786/lor_0297860108_0x630_sci_1.jpg&utc_time=2015-06-29%3Cbr%3E05:03:10%20UTC&description=OpNav+Campaign+4%2C+LORRI+1X1&target=HYDRA&range=18.2M%20km&exposure=150%20msec">JHU Applied Physics Lab</a>.<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-yl4LLcBlB7w/VZPsdEcrLTI/AAAAAAAADGA/b1gWJXihO_Q/s1600/lor_0297860108_0x630_sci_1.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="220" src="http://3.bp.blogspot.com/-yl4LLcBlB7w/VZPsdEcrLTI/AAAAAAAADGA/b1gWJXihO_Q/s320/lor_0297860108_0x630_sci_1.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">New Horizon's image of Pluto and Charon taken on 06/29/2015 at a distance of 18 million km. </td></tr>
</tbody></table>
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://apod.nasa.gov/apod/ap150623.html" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;" target="_blank"><img border="0" height="320" src="http://2.bp.blogspot.com/-yW1QpvrgIf4/VZPoSnUZGzI/AAAAAAAADF0/-kA00rHVjRE/s320/sharpless308_simon_2088_small.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://apod.nasa.gov/apod/ap150623.html" target="_blank">Sharpless 308. Copyright Kfir Simon</a></td></tr>
</tbody></table>
Bubbles. About 5,000 light years away from us is the beautiful Wolf-Rayet (stellar) bubble Sharpless 308. It is about 60 light years in diameter, and only 70,000 years old. The genetically modern human ancestors of ~98% or more of your DNA were present and still hanging out in Africa, but some were about to set off on extended holiday. [Credit: <a href="http://www.pbase.com/tango33/profile" target="_blank">Kfir Simon</a>, as seen on <a href="http://apod.nasa.gov/apod/ap150623.html" target="_blank">APOD</a>]<br />
<br />
Speaking of Wolf Rayet stars, how about Wolf Rayet galaxies? Why, it's a Hubble image of the famous SBS1415+437. (Just kidding, this galaxy is not well known, even among the so-called Wolf Rayet galaxies.)<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://cdn.spacetelescope.org/archives/images/screen/potw1526a.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://cdn.spacetelescope.org/archives/images/screen/potw1526a.jpg" height="159" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The Wolf-Rayet galaxy SBS1415+437. Credit NASA/HST/Aloisi et al?</td></tr>
</tbody></table>
<br />
Go read the background at <a href="http://www.spacetelescope.org/images/potw1526a/">SpaceTelescope.org's Image of the Week</a>. Although it is not clear from the Image of the Week site the image is probably that described in <a href="http://iopscience.iop.org/1538-4357/631/1/L45/fulltext/19727.text.html">Aloisi et al, 2005, ApJ, 631, L45</a> which detected the presence of old (1+ Gyr) stars in SBS1415+437., which had bearing on an old (by now) debate about whether the so-called Wolf Rayet galaxies in the local Universe where young galaxies just experiencing their first burst of star formation (Answer: In general no, they're not). <br />
<br />
I of course chose the bubble, superbubble, Wolf Rayet galaxy, and NGC 6503 images because I did some work on wind-blown bubbles, superbubbles, WR galaxies and NGC 6503 back in the days I was a professional astronomer. Red and green Solar images are for Micah and Caelan, who are very into that type of solar imagery at the moment.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-87511669845875294922015-01-14T09:02:00.000-05:002015-01-14T09:02:26.727-05:00Exciting times in NGC 4666I missed this when it happened in December, but a new Type Ia supernova was discovered in the "nearby" starburst galaxy NGC 4666 by the <strong><a href="http://www.astronomy.ohio-state.edu/%7Eassassin/index.shtml" target="_blank">Automated Sky Survey for SuperNovae (ASAS-SN)</a> </strong>project on December 9th. <a href="http://www.universetoday.com/117715/end-the-year-with-a-bang-see-a-bright-supernova-in-virgo/" target="_blank">Bob King at Universe Today has a nice short article with a finding chart for NGC 4666, and some background information and images of the galaxy</a>. A more recent, early January, <a href="http://earthsky.org/todays-image/supernova-in-the-superwind-galaxy" target="_blank">amateur observation showing the supernova by Justin Ng can be found at EarthSky.org</a>.<br />
<br />
More on this topic some time later...Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-38163111208641625172014-12-23T13:13:00.000-05:002014-12-23T13:13:34.333-05:00High Energy Astronomy NewsTwo items of note:<br />
<ol>
<li><a href="http://www.scientificamerican.com/article/fact-or-fiction-the-explosive-death-of-eta-carinae-will-cause-a-mass-extinction/" target="_blank">Scientific American has a nice article on why the threat to life on Earth from Gamma Ray Bursts, in particular from the dying start Eta Carinae, is not something you need to worry about. </a>(I've discussed putative GRB-caused events here and here).</li>
<li>NuSTAR, an orbitting hard X-ry telescope, has captured some<a href="http://www.nasa.gov/jpl/nustar/pia18906/#.VJmvq0CEAOg" target="_blank"> cool images of hard X-ray emission from the Sun</a> (not a target NuSTAR was expected to look at, being designed for the study of Active Galactic Nuclei millions to billions of light years from Earth).</li>
</ol>
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.nasa.gov/sites/default/files/styles/946xvariable_height/public/thumbnails/image/pia18906-nustarsun.jpg?itok=zOThRL12" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://www.nasa.gov/sites/default/files/styles/946xvariable_height/public/thumbnails/image/pia18906-nustarsun.jpg?itok=zOThRL12" height="202" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The NuSTAR data, seen in green and blue, reveal solar high-energy emission (green shows energies between 2 and 3 kiloelectron volts, and blue shows energies between 3 and 5 kiloelectron volts). The high-energy X-rays come from gas heated to above 3 million degrees. The red channel represents ultraviolet light captured by SDO at wavelengths of 171 angstroms, and shows the presence of lower-temperature material in the solar atmosphere at 1 million degrees. [Image and caption from <a href="http://www.nasa.gov/jpl/nustar/pia18906/#.VJmvq0CEAOg" target="_blank">NASA/JPL</a>]</td></tr>
</tbody></table>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-26526083083441473682014-10-16T07:52:00.001-04:002014-10-16T07:52:58.947-04:00Hooray, Octave supports numpy-style boolean array indexing operationsI've only just discovered that <a href="https://gnu.org/software/octave/" target="_blank">Gnu Octave</a> (the Gnu version of Matlab) supports <a href="http://wiki.scipy.org/Tentative_NumPy_Tutorial" target="_blank">numpy-style boolean array indexing operations</a>, in particular<br />
<ul>
<li>logical operations on vectors to return boolean true/false vectors</li>
<li>array indexing using vectors on vectors</li>
</ul>
An example, using a simple vector a.<br />
<blockquote class="tr_bq">
<blockquote class="tr_bq">
<span style="font-family: "Courier New",Courier,monospace;">octave:2> a=[1 2 3 4 1 2 3 4]<br />a =<br /><br /> 1 2 3 4 1 2 3 4</span><br />
<span style="font-family: "Courier New",Courier,monospace;"></span></blockquote>
</blockquote>
Create a boolean mask called b with all elements of a greater than 2. <br />
<blockquote class="tr_bq">
<blockquote>
<span style="font-family: "Courier New",Courier,monospace;">octave:3> b=a > 2<br />b =<br /><br /> 0 0 1 1 0 0 1 1</span></blockquote>
</blockquote>
Now use b to access only those elements of a that are true in the mask array b. <br />
<blockquote class="tr_bq">
<blockquote>
<span style="font-family: "Courier New",Courier,monospace;">octave:4> a(b)<br />ans =<br /><br /> 3 4 3 4</span></blockquote>
</blockquote>
Why use Octave when we have python/numpy/scipy? Sometimes its just faster to fire up octave to get a look at data, and matlab/octave syntax is much less verbose than python.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-313409825548541952014-08-26T22:43:00.000-04:002014-08-26T22:43:00.037-04:00More on the possible AD 774/775 hit on the Earth by a nearby GRB <a href="http://superwinds.blogspot.com/2014/08/what-happened-in-year-774775.html" target="_blank">I hadn't heard of either the odd AD 774/775 values of the C12/C14 and increased B10 ratios or the hypothesized casue: a nearby (within the Milky Way) Gamma Ray Burst</a> before reading a blog post by Greg Laden related to climate change a while ago.<br />
<br />
It turns out the GRB hypothesis was only recently advanced: Hambaryan & Neuhäuser, 2013, MNRAS, 430, 32 [<a href="http://mnras.oxfordjournals.org/content/430/1/32" target="_blank">full article text available online here</a>]. Back at the time <a href="http://www.slate.com/blogs/bad_astronomy/2013/01/21/earth_hit_by_a_gamma_ray_burst_did_a_cosmic_blast_hit_us_in_775_ad.html" target="_blank">Phil Plait actually covered the story in his blog</a>, which has a nice write up of the idea and why other explanations (Solar Flare, Magnetar, nearby Supernova) are claimed to be less likely than a <a href="https://en.wikipedia.org/wiki/Gamma-ray_burst#Short_gamma-ray_bursts" target="_blank">"short" (neutron-star merger induced) GRB</a>.<br />
<br />
It somewhat surprises me that an event of the magnitude necessary to alter the isotopic composition of the Earth's atmosphere in less than a few seconds could occur without (a) anyone seeing anything and recording it, and more over (b) not causing any significant biological events (e.g. animal, plant or human deaths). Still, reality often runs counter to naive expectation (i.e. "common sense") so I'm not too put off the idea by that.<br />
<br />
For now I'd view this idea of the Earth getting hit by a short GRB as a plausible hypothesis rather than concrete fact, at least until several more studies come to the same conclusion. Still, it is a rather fun and exciting idea.Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-42079143649685110912014-08-01T22:48:00.000-04:002014-08-01T22:48:00.249-04:00What happened in the year 774/775?Something odd happened to the Earth around the year 774/775. For the background, head over to <a href="http://scienceblogs.com/gregladen/2014/07/30/volcanoes-tree-rings-and-climate-models-this-is-how-science-works/" target="_blank">Gred Laden's blog, where this is just part of a larger question about climate reconstruction</a>.<br />
<br />
A few exerts follow to give you a taste of what caught me eye.<br />
<br />
<blockquote class="tr_bq">
A long time ago, probably in our galaxy but kind of far away, a cosmic event happened that caused the Earth to be bathed in Gamma rays in AD 774 or 775.<br />
...<br />
There is chemical and physical evidence, though, of the Gamma ray
burst. The best evidence is the large scale conversion of stable
Nitrogen isotopes into unstable Carbon–14 isotopes in the upper
atmosphere. As you know, radioactive (meaning, unstable) Carbon–14 is
created continuously but at a somewhat variable rate in the upper
atmosphere. Some of that Carbon is incorporated, along with regular
stable Carbon, into living tissues. After the living tissue is created
and further biological activity that might retrofit some of the Carbon
atoms ends (i.e., the thing dies) the ratio of radioactive Carbon to
stable Carbon slowly changes as the radioactive Carbon changes back into
Nitrogen. By measuring the ratio now, we can estimate how many years
ago, plus or minus, the originally living thing lived and died.
But it does vary. Solar activity, nuclear testing, other things, can
change the amount of Carbon–14 that gets produced. <b>And, a cosmic event
that happened in 774/775 caused the production of enough Carbon–14 to
throw off the chronology by hundreds of years.</b> </blockquote>
<br />
Now why haven't I heard of this event before? How certain are we that it was a Gamma Ray Burst, and if so, where was the source? Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-6572900451081546092014-07-24T18:30:00.000-04:002014-07-24T18:30:00.443-04:00Fifteen years in orbit and awesome: The Chandra X-ray ObservatoryYesterday, July 25rd, 2014, marked the 15th anniversary of the launch of one of NASA's Great Observatories: the Chandra X-ray Observatory. I was one year into my first post-doc at Johns Hopkins at the time, and watched the launch in one of the conference rooms on the 1st floor. Later I spent many years working on data from Chandra. I can't believe its been so long.<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://chandra.harvard.edu/graphics/resources/illustrations/launch/99pp0957-72.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://chandra.harvard.edu/graphics/resources/illustrations/launch/99pp0957-72.jpg" height="157" width="200" /></a></div>
<br />
Over-views of the 15 years of Chandra:<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://chandra.harvard.edu/graphics/resources/illustrations/deploy/sts93_deploy1-72l.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://chandra.harvard.edu/graphics/resources/illustrations/deploy/sts93_deploy1-72l.jpg" height="200" width="196" /></a></div>
<ul>
<li><span id="goog_1360376330"></span><a href="http://space.io9.com/celebrate-chandra-with-supernova-and-pulsars-1609305975/+katharinetrendacosta" target="_blank">"Chandra Has Been X-Raying the Universe for 15 Years" on i<span id="goog_1360376334"></span><span id="goog_1360376335"></span>o9<span id="goog_1360376331"></span></a>.</li>
<li><a href="http://www.nasa.gov/chandra/news/chandra-15th-anniversary.html" target="_blank">NASA's Chandra X-ray Observatory Celebrates 15th Anniversary at NASA.gov</a>.</li>
<li><a href="http://chandra.harvard.edu/press/14_releases/press_072214.html" target="_blank">NASA's Chandra X-ray Observatory Celebrates 15th Anniversary at the Chandra X-ray Observatory website.</a> </li>
</ul>
<br />
For information on the accompanying press release image <a href="http://chandra.harvard.edu/photo/2014/15year/" target="_blank">go here</a>.<br />
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<a href="http://chandra.harvard.edu/photo/2014/15year/15year.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://chandra.harvard.edu/photo/2014/15year/15year.jpg" height="392" width="640" /></a></div>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-44970813993179543552014-07-21T07:33:00.000-04:002014-07-21T07:33:16.779-04:00An introduction to quantitative astrophotography on Linux: Part 2 - RAW to FITS and Dark FramesIn part 1 of this series I introduced my reasons for wanting to look into what I called quantitative astrophotography, by which I mean getting god quantitative estimates of the performance of a very simple, entry level, set of DSLR images of the night sky. I wanted to control and understand the quantitative changes made to the images, and hence chose to avoid the Windows-based GUI software common in the amateur astronomy world. Instead I'll use standard astronomical data reduction and analysis techniques and stick to open source tools running under Linux (actually in this case, OSX with macports).<br />
<br />
By the end of part 1 I was in possession of ~30 RAW images taken with a Canon Digital Rebel XTi, including a series of dark frames and bias frames. This article covers the next step in the process: converting the RAW images into FITS format, along with a quick look at the dark frame properties. The process of finding the bad pixels and removing them from the images will be covered in Part 3.<br />
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<a href="http://4.bp.blogspot.com/-1oXIIldpZug/UwyMsTeSENI/AAAAAAAACqc/ZN7ABjbZRiw/s1600/Basic+Data+Reduction+-+New+Page.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Dark frame and bad pixel data reduction flow chart" border="0" src="http://4.bp.blogspot.com/-1oXIIldpZug/UwyMsTeSENI/AAAAAAAACqc/ZN7ABjbZRiw/s1600/Basic+Data+Reduction+-+New+Page.png" height="245" title="Dark frame and bad pixel data reduction flow chart" width="400" /></a></div>
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<div class="separator" style="clear: both; text-align: center;">
</div>
The flow chart summarizes the actions that need to be performed on the RAW images to end up with FITS images that have had the bad pixels, the dark current and the bias removed.<br />
<br />
The basic idea behind astronomical imaging is to use a series of calibration images to improve the final image of the target. At these early stages of reduction we're talking about using dark frames, bias frames, and bad pixel masks to remove the additional signal in the image that is not from the sky, but from the detector electronics itself. Originally I wrote a lengthy description of each of these calibration image types, but I know think it is better just to point interested readers at more extensive discussions at:<br />
<ol>
<li><a href="http://starizona.com/acb/ccd/advimcal.aspx" target="_blank">Starizona's Guide to CCD Imaging</a>.</li>
<li><a href="http://www.astro.uni-bonn.de/~mischa/datareduction.html" target="_blank">Mischa's Data Reduction web page at the University of Bonn</a>.</li>
</ol>
<br />
The other reason I decided to cut down on the terminology discussion is that is very CCD-centric, as they are the classic detector type used in professional astronomy. However digital cameras almost always use CMOS detectors and not classic CCDs. The on-Camera data processors inside digital camera perform operations that alter the data values in ways that professional CCD imagers do not.<br />
<h3>
dcraw to FITS.</h3>
To create a FITS file from a RAW file we use the -c flag on the dcraw command line and pipe the output into a program that can convert PNM format to FITS. The dcraw web page recommends pnmtofits, e.g.<br />
<pre>dcraw -c (other_flags) input_image.cr2 | pnmtofits > output.fits
</pre>
<br />
However there is one problem with this. dcraw and many image processing utilties assume the first pixel is the top left of an image, whereas the FITS conventsion is the first pixel is the bottom left. So FITS files created with pnmtofits are upside-down. ImageMagick is smart enough to know about fits and corrects for this, so we can make correctly-oriented FITS files like this:<br />
<pre>dcraw -c (other_flags) input_image.cr2 | convert pnm:- output.fits
</pre>
<br />
<h3>
Dark and/or Bias Frame Creation</h3>
The dark and bias frames are not exposed to light, so the Bayer RGB mask on top of the detector is not important and the signal doesn't depend on whether each pixel is R, G or B. This means we convert the RAW file to a single channel (grayscale) image for analysis.<br />
<br />
It is important that both the raw count output from the camera's ADU and image orientation are preserved, i.e. no gamma correction or histogram manipulation should be performed on the raw file. We want the exact 12-bit (or <a href="http://www.learn.usa.canon.com/resources/articles/2011/14-bit_ad_conversion_digic4_article.htmlp" target="_blank">14-bit</a> if you have a newer camera) values [except that we cannot control what the Camera's image processor does to the RAW images].<br />
<br />
The corresponding dcraw command line options are -D -4 -j -t 0. Hence for each raw format dark and/or bias frame we initially run the following command to convert to FITS:<br />
<pre>dcraw -c -D -4 -j -t 0 input_dark.cr2 | convert pnm:- output_dark.fits
</pre>
<br />
<h3>
Dark and Bias Frame Statistics</h3>
The following table summarizes some simple statistical properties of all the dark and bias frames I took. The file name also contains the ISO value (400, 800 or 1600) and whether bad pixel had been removed in the dcraw to FITS conversion, where "nobadpix" means "no bad pixel removal". We'll deal with the bad pixel identification and removal in the next post.<br />
<br />
<!-- Without Bad Pixel removal -->
<br />
<table border="1">
<tbody>
<tr><th>File</th><th>Rows</th><th>Cols</th><th>Mean +/- StdDev</th><th>Median</th><th>Minimum</th><th>Maximum</th></tr>
<tr><td>Prior to bad pixel removal</td></tr>
<tr><td>dark_0694_t30.0_800_Sat_Jan_18_22:04:46_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.11 +/- 6.39</td><td>256.50</td><td>170.5</td><td>4056.5</td></tr>
<tr><td>dark_0695_t30.0_800_Sat_Jan_18_22:05:41_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.11 +/- 6.34</td><td>256.50</td><td>177.5</td><td>4056.5</td></tr>
<tr><td>dark_0696_t30.0_1600_Sat_Jan_18_22:06:22_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.42 +/- 10.89</td><td>257.50</td><td>95.5</td><td>4057.5</td></tr>
<tr><td>dark_0697_t30.0_1600_Sat_Jan_18_22:06:57_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.38 +/- 10.84</td><td>257.50</td><td>105.5</td><td>4057.5</td></tr>
<tr><td>dark_0698_t30.0_400_Sat_Jan_18_22:07:40_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>255.99 +/- 4.03</td><td>255.50</td><td>219.5</td><td>4055.5</td></tr>
<tr><td>dark_0699_t30.0_400_Sat_Jan_18_22:08:14_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.00 +/- 4.02</td><td>255.50</td><td>218.5</td><td>4055.5</td></tr>
<tr><td>bias_0700_t0.00025_400_Sat_Jan_18_22:09:03_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>255.99 +/- 2.95</td><td>255.50</td><td>210.5</td><td>333.5</td></tr>
<tr><td>bias_0701_t0.00025_400_Sat_Jan_18_22:09:09_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.00 +/- 2.94</td><td>255.50</td><td>216.5</td><td>328.5</td></tr>
<tr><td>bias_0702_t0.00025_800_Sat_Jan_18_22:09:21_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.09 +/- 4.98</td><td>256.50</td><td>175.5</td><td>397.5</td></tr>
<tr><td>bias_0703_t0.00025_800_Sat_Jan_18_22:09:23_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.09 +/- 4.98</td><td>256.50</td><td>185.5</td><td>394.5</td></tr>
<tr><td>bias_0704_t0.00025_1600_Sat_Jan_18_22:09:31_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.39 +/- 9.27</td><td>257.50</td><td>101.5</td><td>531.5</td></tr>
<tr><td>bias_0705_t0.00025_1600_Sat_Jan_18_22:09:32_2014_nobadpix.fits</td><td>2602</td><td>3906</td><td>256.39 +/- 9.27</td><td>257.50</td><td>99.5</td><td>534.5</td></tr>
<tr><td span="3">Bad pixels removed</td></tr>
<tr><td>dark_0694_t30.0_800_Sat_Jan_18_22:04:46_2014.fits</td><td>2602</td><td>3906</td><td>256.10 +/- 5.04</td><td>256.50</td><td>193.5</td><td>320.5</td></tr>
<tr><td>dark_0695_t30.0_800_Sat_Jan_18_22:05:41_2014.fits</td><td>2602</td><td>3906</td><td>256.10 +/- 5.04</td><td>256.50</td><td>177.5</td><td>693.5</td></tr>
<tr><td>dark_0696_t30.0_1600_Sat_Jan_18_22:06:22_2014.fits</td><td>2602</td><td>3906</td><td>256.40 +/- 9.41</td><td>257.50</td><td>95.5</td><td>1047.5</td></tr>
<tr><td>dark_0697_t30.0_1600_Sat_Jan_18_22:06:57_2014.fits</td><td>2602</td><td>3906</td><td>256.36 +/- 9.39</td><td>257.50</td><td>105.5</td><td>670.5</td></tr>
<tr><td>dark_0698_t30.0_400_Sat_Jan_18_22:07:40_2014.fits</td><td>2602</td><td>3906</td><td>255.99 +/- 2.96</td><td>255.50</td><td>219.5</td><td>451.5</td></tr>
<tr><td>dark_0699_t30.0_400_Sat_Jan_18_22:08:14_2014.fits</td><td>2602</td><td>3906</td><td>255.99 +/- 2.95</td><td>255.50</td><td>218.5</td><td>316.5</td></tr>
<tr><td>bias_0700_t0.00025_400_Sat_Jan_18_22:09:03_2014.fits</td><td>2602</td><td>3906</td><td>255.99 +/- 2.95</td><td>255.50</td><td>210.5</td><td>307.5</td></tr>
<tr><td>bias_0701_t0.00025_400_Sat_Jan_18_22:09:09_2014.fits</td><td>2602</td><td>3906</td><td>256.00 +/- 2.94</td><td>255.50</td><td>216.5</td><td>299.5</td></tr>
<tr><td>bias_0702_t0.00025_800_Sat_Jan_18_22:09:21_2014.fits</td><td>2602</td><td>3906</td><td>256.09 +/- 4.98</td><td>256.50</td><td>175.5</td><td>341.5</td></tr>
<tr><td>bias_0703_t0.00025_800_Sat_Jan_18_22:09:23_2014.fits</td><td>2602</td><td>3906</td><td>256.09 +/- 4.98</td><td>256.50</td><td>185.5</td><td>340.5</td></tr>
<tr><td>bias_0704_t0.00025_1600_Sat_Jan_18_22:09:31_2014.fits</td><td>2602</td><td>3906</td><td>256.39 +/- 9.27</td><td>257.50</td><td>101.5</td><td>418.5</td></tr>
<tr><td>bias_0705_t0.00025_1600_Sat_Jan_18_22:09:32_2014.fits</td><td>2602</td><td>3906</td><td>256.39 +/- 9.27</td><td>257.50</td><td>102.5</td><td>434.5</td></tr>
</tbody></table>
<br />
<br />
We can immediately see that the RAW values have been altered by the on-camera image processing chip.<br />
<ol>
<li> The mean and median values of all the dark frame and bias frames are essentially 256+/-1, irrespective of whether it is a 30 second dark frame or a 1/4000'th of a second bias exposure, and irrespective of the ISO value or whether bad pixels have been removed. That value of 256 is 2^8, which would be highly suggestive of a camera-processor induced value even if we didn't already suspect some on-board processing of the RAW frames.</li>
<li>The standard deviations of the mean don't relate the mean values. </li>
</ol>
In the next post in this series we will look at bad pixel detection and removal using dcraw. <br />
<ol>
</ol>
Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0tag:blogger.com,1999:blog-28625384.post-54071029044245474992014-07-11T19:30:00.000-04:002014-07-11T19:30:00.206-04:00How much does a square root cost?An interesting diversion: how much (time) does calling the square root function sqrt() cost, and is it even worth trying alternative less-accurate implementations?<br />
<br />
<a href="http://assemblyrequired.crashworks.org/2009/10/16/timing-square-root/" target="_blank">Some Assembly Required provides some answers: </a><br />
<div align="center">
<b><u>SQUARE ROOT</u></b>
<table border="" class="padded">
<tbody>
<tr>
<th>Method</th>
<th>Total time</th>
<th>Time per float</th>
<th>Avg Error</th>
</tr>
<tr>
<td>Compiler <code>sqrt(x)</code> /<br />x87 FPU <code>FSQRT</code></td>
<td>404.029ms</td>
<td>24ns</td>
<td>0.0000%</td>
</tr>
<tr>
<td>SSE intrinsic <code>ssqrts</code></td>
<td>200.395ms</td>
<td>11.9ns</td>
<td>0.0000%</td>
</tr>
<tr>
<td>Carmack’s Magic Number rsqrt * x</td>
<td>72.682ms</td>
<td>4.33ns</td>
<td>0.0990%</td>
</tr>
<tr>
<td>SSE <code>rsqrtss</code> * x</td>
<td>20.495ms</td>
<td>1.22ns</td>
<td>0.0094%</td>
</tr>
<tr>
<td>SSE <code>rsqrtss</code> * x<br />with one NR step</td>
<td>53.401ms</td>
<td>3.18ns</td>
<td>0.0000%</td>
</tr>
<tr>
<td>SSE <code>rsqrtss</code> * x<br />with one NR step, unrolled by four</td>
<td>48.701ms</td>
<td>2.90ns</td>
<td>0.0000%</td>
</tr>
</tbody></table>
</div>
<div align="center">
<b><u>RECIPROCAL SQRT</u></b>
<table border="" class="padded">
<tbody>
<tr>
<th>Method</th>
<th>Total time</th>
<th>Time per float</th>
<th>Avg Error</th>
</tr>
<tr>
<td>Carmack’s Magic Number rsqrt </td>
<td>59.378ms</td>
<td>3.54ns</td>
<td>0.0990%</td>
</tr>
<tr>
<td>SSE <code>rsqrtss</code></td>
<td>14.202ms</td>
<td>0.85ns</td>
<td>0.0094%</td>
</tr>
<tr>
<td>SSE <code>rsqrtss</code> <br />with one NR step</td>
<td>45.952ms</td>
<td>2.74ns</td>
<td>0.0000%</td>
</tr>
<tr>
</tr>
</tbody></table>
</div>
<br />Dave Stricklandhttp://www.blogger.com/profile/07992496303240856722noreply@blogger.com0