The Starry Night, 136

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01/16/2015. An afterthought... So there I was setting up deep narrowband images when I thought, there's no sense wasting this sparkling winter sky while I stand here blinding myself staring at the computer hunting a guide star and scripting exposures for the rest of the night.

I put an ancient Nikon prime lens on the Canon 6D and mounted the camera on the iOptron SkyTracker. I had it shoot 30-second widefield views while I fumbled with deep-sky esoterica.

 

Lovejoy and the Pleiades

Comet Lovejoy and the Pleiades
8x30s (4 min total), Canon 6D @ iso 1600
135mm F2.0 Nikkor @ F2.8

iOptron SkyTracker

 


I did another set of close-ups of the comet's head between finishing up the triptych of IC 1805 and another go at the Rosette (the overnight target). Stay tuned.

 

1/17/2015. Note that the 135mm's field is anything but flat -- I mean that the top is beautifully focused while the middle is bloated and the bottom is worse. Turns out that the Nikon lens flange was loose, that the 5 or 6 screws that secure the Nikon bayonet to the body of the lens had backed out. Fixed. Followed by a comedy of errors (kicking the tripod, grossly misaligning the tracker, clouds...). I won't be showing off the lens's nicely improved performance tonight. With the R-C, I took a few narrowband images of the brightest part of the nebula associated with IC 1805, NGC 896, but got nothing worth your bandwidth yet. I'm using this often-cloudy night to rebuild my dark library. I accidentally tossed its most recent additions when I archived 2014's photos to recover space for 2015's. See errors, comedy of, above.

And in the morning, I somehow managed to get only 5 of my 16 scheduled 900s darks. I have no idea how, but I somehow misplaced them between here at the desk and out there at the telescope.

So I did something instructive: I opened three master darks. One from 2011, one from 2013, and the latest one from last night, all -30°C and 900s. I used one of them for the R channel, one for G, and one for B, then cast a critical eye on the resulting color image. If all the noise were white, that would imply that the darks have changed very little over the years. And you know what? The bright pixels are overwhelmingly white! In fact, all the eye-catchingly bright ones are white. There is not a single ruby, emerald, or sapphire to be seen. An even more compulsive fellow would say that this demands statistical analysis -- how much variation at what brightness levels, etc. -- but I'm happy to say that the strong impression is that newer darks resemble older ones. Oh, sure, when you look way down in the weeds, there's some variation, but by and large, it's safe to use older darks.

 

1/18/2015. Through high haze, a close look at Comet Lovejoy. I took 20 images through the clear filter and 8 each through R, G, and B. No flats, no darks, no guiding. that's as close to point-and-shoot as you get with a CCD.

 

lovejoy

Comet Lovejoy
AT10RC @ F5
20x30s C + 8x30s RGB (24 min tota
l)

 

 

1/18/2015. A not-quite-so-close-up from last night shows Comet Lovejoy's tail streaming out across the stars of Aries. A 10-inch F4 Newtonian and full-frame DSLR provide this wider view ("wider" compared to the 10-inch F8 R-C and a much smaller CCD). Acquiring the night's images was easy; processing them has so far been a real pain. I have ~100 subframes ranging from 30 seconds to 2m30s; this image is made up from only four of them, manually aligned.

 

lovejoy

Comet Lovejoy
10" F4 Newtonian, Baader MPCC-III
Canon 6D @ ISO 1600
4x150s (10 min total)

 

1/19/2015. Just ahead of a solid overcast, I sneaked one more peek at the comet. Focus is better, the sky slightly worse. I tried one stop more gain on the camera (iso 3200 rather than 1600) and again took much more data than I know how to handle. There are four images combined below and 20 or so more (plus a ton of 30s exposures) on the disk waiting for revelation. I had PixInsight align the stars and then worked with the registered versions of the images. I loaded them into PixInsight one at a time, histogram stretched each, did a couple of background extraction passes set to divide, one more set to subtract, then took one more cut at histogram transformation. Then stacked them. The short focal length (1000mm), the short interval (10 min), and the 35mm sensor work together to keep the comet from trailing too much, but even so, there is more fine-scale detail (dimly) visible in each frame than in the (brighter) stack below. I recovered some of that detail with a deconvolution pass designed to undo trailing. That messed up the stars a bit. None of it matters very much in web-sized presentations. There's a lot to learn about deep images of moving targets.

 

Lovejoy

Comet Lovejoy
10" F4 Newtonian, Baader MPCC-III
Canon 6D @ ISO 3200
4x150s -- 10 min total
Click the image for a better view.



1/24/2015. A crescent Moon added a note of urgency to tonight's clear skies: have a look at Comet Lovejoy near its brightest before it is washed out for a couple of weeks. Tending the telescope made me a lousy host for a dinner get-together with the one and only Julia Davis and her equally incomparable father and son.

In 7x50's, the comet is just a fuzzball under my skies; in the 80mm Orion Short-tube (which serves as the finder on the 10-inch Newtonian), the coma is just elongated enough to be confident about where the tail must be. But on the chip, it remains a magnificent sight.

 

Lovejoy

Comet Lovejoy (and the NGC 1060 galaxy group)
10" F4 Newtonian, Baader MPCC-III
Canon 6D @ ISO 3200
4x150s -- 10 min total
(Check the next page for an improved view.)


The galaxy group at upper right was a bonus. I glimpsed the brightest member (12th magnitude NGC 1060) in one of the 150 second subframes and made sure to bring it up in the finished image; another dozen or so galaxies followed. Click the link for a better view.

 


 
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