The Starry Night, 88

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4/16/2012. Reinventing wheels! It's been a little too long since I did the deep-sky thing, and when I uncovered the Ritchey, removed the pollen wrap from the CCD, reattached control and power cables, found a star to focus on... troubles were just beginning. I forgot that I had put the focal reducer on the CCD to provide some dust and pollen protection so I spent half an hour hunting for focus miles (inches) from where it actually was. Then had to remember that without the FR, I needed a 2-inch extension. Then had to remember where it was, and go get it. I need to remove some of the Teflon shims to let Robofocus lift the camera reliably (until then, a helping hand will do). Bugs -- literally. Moths, gnats and mosquitos filled this abnormally sweaty April night. The CCD would only cool to -25C. And the goto was miscalibrated owing to... what?

Setup was reminiscent of the bad old days until I managed to walk the telescope onto Mars, then centered Regulus, on which I recalibrated and focused, and finally slewed to M95. I had to remember how to set the guiding, then remember where Maxim had hidden the options, but I finally got things more or less dialed in. I focused using the Bahtinov mask, only, and decided not to drive myself crazier trying to minimize FWHM by the numbers. I collected seven light frames, some fresh darks at this balmy temperature, and a decent set of flats just before calling it a night.

The result is not bad:



M95 w/Supernova 2012aw
7x900s L (1h45m)
ST2000XM @ -25C

M95 shines across ~40,000,000 light-years in Leo. It's about 80% the mass of the Milky Way. Supernova 2012aw (the bright star at the intersection of the red tick marks) erupted on March 16. It's a type-II, core-collapse supernova, and in this photo it's still within a few tenths of a magnitude of maximum.




4/20/2012. I began the night trying to photograph the hurtling moons of Barsoom, and then took a good cut at gathering color data to add to the M95 image above. Neither effort was particularly successful. Deimos was likely hidden by a diffraction spike and Phobos by both the glare of the planet and a diffraction spike. I got a decent red frame of M95 but intermittent clouds prevented me from getting good 900s green and blue frames. Around midnight, I finally landed some kind of blue frame (using 20s guiding subs to peer through thickening clouds). Despite the 900s RGB integrations, the color frames are very weak. It will be a few nights before the Moon is troublesome, and odds are good that one will be clear enough to use. In the meantime, this is the best I've got:


m95 color

M95 w/Supernova 2012aw
Above L data + 900s RGB


5/04/2012. Clouds, haze and the growing Moon did keep me from adding color to M95 during the last couple of weeks. Instead, I spent a couple of nights experimenting with the Moon itself. I found a solid focal point for the Point Grey Chameleon (2-inch extension, barlow inside 1.25-inch snout, AT focuser out around 4cm). Turns out that the FL this produces is probably not quite long enough to get the most from the 'scope (or so I gather from this essay by Roland Christen about his experiences with his 10-inch Mak). I'm relatively pleased with the results, especially since the Moon was only 27 degrees up and rippling in the evening air by the time I got everything playing together. I took several 300-frame and a few long-run video clips. Here's one of the best of the lot:



8ms x 886
AT10RC @ F14


I did get the rille in the floor of the Alpine Valley, just, and Hadley Rille, just, and some decent detail on the floor of Ptolemeaus (above). Nice start. Please don't compare mine to these by Wes Higgins or others by Alan Friedman. I need to get closer to their standard before reopening the "Howling at the Moon" section of the Slow Blog. If and when I get there, I'll tell you what worked and what didn't. One thing worth trying: imaging through a color filter. Even though the Ritchey should be perfectly achromatic, the atmosphere isn't. Alan uses a green filter for his spectacular lunar photos. Worth a few hundred shots.


5/16/2012. Taking a lesson from sungazing advances, I've tried reprocessing my recent moon clips with AVIStack set to use only the best 30-40% of the frames. The improvement is substantial! A solar continuum filter is on order, and I think there is enough light to take advantage of its monochromatic charactertistics to remove a lot of atmospherics from lunar photos, too. If the Moon will please sit still for another portrait session in late May or early June, I think I will have some interesting show and tell.


6/19/2012. I've been sunstruck these last few weeks, as you can tell from the scarcity of updates in this part of the slowblog. I am back with a few tricks, like imaging in narrow bandwidths to handle seeing. In particular, imaging in the NIR with a Baader 685 IR-pass filter seems to work very nicely. Today I put the Ritchey back on the mount, removed some of the excessive shimming in the focuser, found a good focus for the PGR Chameleon behind a Maxbright diagonal (the better to take up backfocus and trim IR on the long side of 700nm), and set about imaging Saturn in the twilight as it skipped in and out of clouds, through a gap in the pines:



Saturn with the AT10RC
PGR Chameleon w/Baader 685 and Barlow
best 1000 frames out of 2,400
blended with all 2,400
65ms, 12db, gamma 1.00


Don't be too impressed: it looks good because it's small. Promising though -- the inner crepe ring(?), Cassini's Division all the way around, the shadow of the rings, the shadow of the planet on the rings, the dark polar hood, one good belt and hints of others. Not too shabby for what's supposedly an exclusively deep-sky instrument with an almost 50% central obstruction. I may not get the SBIG CCD out again until I get the 12vDC power distribution redone with Anderson Power Poles (almost there, waiting for some blade fuses to arrive and for ideas about cable management to settle). In the meantime, there's plenty to learn about solar system imaging with the USB-powered Chameleon.



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 LRGB and 7nm H-a filters. The internal guide chip of the CCD most often keeps the OTA pointed in the right direction (I'll let you know when a Meade DSI and a separate 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. Maxim performs image calibration, alignment, and stacking; Photoshop CS4 and FocusMagic 3.0.2 take it from there. Gradient Xterminator by Russell Croman and Astronomy Tools by Noel Carboni see their share of work, too. Beginning in May 2013, PixInsight has taken over some of the heavy lifting for transfer function modification and deconvolution.


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                   © 2012, David Cortner