The Starry Night, 156

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Sublime, meet Ridiculous...

One link for for people who come here to see pretty pictures, another for the hard-bitten amongst us who can't wait to read all about DSLR noise characteristics.


10/27/2015. At the communal dinner at St. John's homecoming, Pastor Ann Kelly told me about a friend of hers from seminary who's into astrophotography. I wanted to show off my stuff without sending civilians into the hundreds of wordy pages of the Slowblog (vanity! vanity! all is vanity, I hope the preacher sayeth not). So I put together a gallery using the Wowslider utility and customized the resulting code:



Click to go to
The Best of the Slowblog


If you go there, be sure to move your cursor off the first image; that's how you freeze the show to stare, agog, at whate'er has rendered you gog.

Now I need to enforce some naming conventions and work out some auto-generation tools to make it work more conveniently for this and for other folio uses. When adding images, for example, it's very easy to lose all the custom touches applied before. (Of course, I also checked out Brian Peterson's photos. He does nice work, uses similar equipment, seems to have a thing for many of the same targets.)


And now, the ridiculous: I started collecting darks for the 6D and 50D at typical nighttime temperatures. The usual overnight misadventues followed. The 50D's battery doesn't last even half as long as the 6D's. It's best if remote release / intervalometers actually stay plugged in. A few early lessons: the 50D seems incredibly sensitive to temperature. The standard deviation among all pixels is over twice as great at ~60°F as at ~50°F. The 6D is not exactly immune from temperature effects, but it seems considerably less prone to thermal noise (raising the temperature from 35F to 70F increases the noise in the 50D by 6x but only by 3x in the 6D). All this suggests I need to be much more careful than I have been about recording the actual temperature of my lights and darks, and I should maintain a more extensive dark library than has been my practice, especially when using the modded 50D. Here's one of those stultifyingly arcane tables of image characteristics for my DSLRs. I produced these analyses while working on the dark library.


Undirected maundering and musing. At worst, the dark library data suggest that a cooling box would be useful even if it doesn't provide much refrigeration. Holding a constant, known temperature would go far toward managing noise. On another front, I find myself taking note of motherboards, memory, CPU's, and power supplies for a dedicated machine for image processing. Also prowling eBay comparing Xeon and i7 systems just behind the curve (for affordability) but loaded with RAM and a turnkey OS (because life is short). The benchmarks at PixInsight suggest I could be within a factor of 2 of the leading edge pretty casually; that would be about 10x faster than my current computer. The right box and a fast SSD would do nicely. We know where this will end, but when and exactly how is up for grabs. I have used the prospect of a fast processor to beat back the temptation to put a used Gemini system on the G11. That's really only needed for the narrow-field CCD / R-C combination Out West. If you're going to use it out in the dark, you'll have to drive it there. And if you're driving Out Yonder, then you might as well pack up the Mach1 too. That's why it's portable, right? Also, we know that timed slews from guideposts in the sky work. They take some planning, but they work. I don't want to pay for Gemini and I really don't want the headache of installing, fine-tuning, and providing more power. Let's just not. Not today anyway.




Except where noted, deep-sky photos are made with an SBIG ST2000XM CCD behind a 10-inch Astro-Tech Ritchey-Chretien carried on an Astro-Physics Mach1GTO. The CCD is equipped with Baader wide- and narrow-band filters. The internal guide chip of the CCD most often keeps the OTA pointed in the right direction (I'll let you know when an OAG or guidescope takes its place). Camera control and guiding are handled by Maxim DL 5.12. The stock focuser on the AT10RC has been augmented with Robofocus 3.0.9 using adapters turned on the lathe downstairs. A Canon 6D and a modded 50D find themselves mounted on an Orion 10" F4 Newtonian or carrying widefield glass on an iOptron Skytracker. Beginning in May 2013, PixInsight has taken over more and more of the heavy lifting -- alignment, stacking, gradient removal, noise-reduction, transfer function modification, color calibration, and deconvolution. Photoshop CS4 et seq and the Focus Magic plugin get their licks in, too.


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                   © 2015, David Cortner