The Starry Night, 194

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I'm back! And back to basics. Sort of.

2020/11/30. One of the nicest innovations to come down the pike while I was away from the Slowblog is the ASair from ZWO Electronics. It's a Raspberry Pi computer loaded with software for astronomical imaging -- camera control, data collection, sequencing, polar alignment, plate solving, and guiding. I'm only using a fraction of all that for reasons we'll probably get into sooner or later, but what I am using (camera control and data collection) already makes it a game-changer.

Why? Because I can use the deep-sky camera without a notebook computer, at last. The notebook is the big power drain in the field, and it introduces a lot of bulk and complexity. That said, doing without it takes some getting used to, too. In fact, I've added a Panasonic Toughbook loaded with all the right tools to the traveling kit because I do not want to finally get back out west only to find that I don't know how to get the ASIair to do what I want while time's wasting.

Anyway, by way of getting something started again: here's a (piss-poor) photo of NGC 7000 and Deneb, a crop from a frame from the ASI1600MM:



N7000, 60x60s. ASI1600MM, -25C, gain 300.
135mm Nikkor @ F2.0, 7nm Baader H-a filter.
iOption SkyTracker (original model).
Stars and Nebulae processed separately.
(Click the pic for a larger view.)




The ASIair Velcroed to back of the SkyTracker
135mm Nikkor on ASI1600MM w/extra-long dew shield.


I used this rig to capture the NGC 7000 image above low over the pines. Tracking was off. On the up-side, the new battery pack worked flawlessly (33AH: 4, 12v DC; 2 USB; voltage display; more about that soon).

Today I got very aggressive in processing last night's take, eventually splittiing the nebular and stellar components via PixInsight's Starnet module and then treating each on its own before recombining them as Photoshop layers.

On the mechanical front, I superglued the ArcaSwift plate that mates the SkyTracker to the ball head on the tripod (held just by one 1/4x20 screw, it had turned several degrees over the course of last night's exposures, which couldn't have helped and might be responsible for the degraded tracking). In the interest of cleaner stars and more even field illumination, I've removed the long dew shield in favor of a 72 to 58mm step-down ring. If I just closed the diaphragm (to F2.8, say), I'd get diffraction spikes which would give up some, most, or all the advantage of using less than the lens's full aperture. The step-down ring should do all the good stuff without introducing conspicuous diffraction artifacts (I did this with the 180mm F2.8 for the same reason many pages ago, and that worked great). Now: another clear night, please.

By and by, I've got about three years' stuff to catch up on here. All the way back to the 2017 total eclipse. The good thing for readers is that I only remember the interesting stuff, so you'll be spared a lot of dead-ends and really dull verbiage. Maybe.



My deep-sky photos are made with a variety of sensors and optics. Deepest images come now from a ZWO ASI1600MM Cooled Pro CMOS camera. A good many images come from an unmodded Canon 6D. Video and video extracts begin in a Canon EOS M, usually running in crop mode via Magic Lantern firmware. Telescopes include an AT10RC (a remarkable budget Ritchey-Chretien astrograph), an Orion 10" F4 Newtonian, and a pair of apochromats: a TMB92SS and a AT65EDQ. A very early Astro-Physics 5" F6 gets some use, too. So do lots of camera lenses on both the ASI1600 and the Canon 6D. A solar Frankenscope made using a 4" F10 Orion achromat and the etalon, relay optics, and focuser from a Lunt 60 feeding a small ZWO camera will see more action as the Sun comes back to life. Mounts include an iOpton SkyTracker (original model), a Losmandy G11 (non-Gemino), and an Astro-Physics Mach1 CP3. Software is PixInsight for heavy lifting and Photoshop for polish.


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                   © 2020, David Cortner