The Starry Night, 77

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12/15/2011. Just thinking about this. I'm thinking that this would be a good point at which to draw a line and say: the past is prologue. It feels as if all the tools are now in place. I'm thinking of leaving the previous 76 pages up as a long lesson in getting my shit together and starting this journal fresh. So many of the early lessons seem slap-to-the-forehead obvious. I think maybe the new year will mark a restart on my astronomical notekeeping. It feels to me as if I've graduated from high school imaging and been accepted into a nice undergrad program.

Everything has changed since the beginning: the 5-inch A-P feeding a DSLR riding on a Losmandy G11 served well. That kit let me discover much that made the difference between mediocre and respectable images. Telescope, mount, and camera have all changed. Methods, too, have been replaced wholesale. Much that was trial and error is now routine; refinement, not discovery, is the order of the day. In the beginning, little if anything was quantitative, systematic, or computer-assisted. But good short-focus glass is forgiving, and nice photos happened from time to time (my first APOD was eight years ago!).

Now the kit is a Ritchey-Chretien riding a Mach1GTO and feeding an SBIG CCD. Analysis and adjustment is by way of measurement. Lessons from archery: I'm concentrating on making sure that everything happens exactly the same way except when selected details are intentionally adjusted. In the beginning, I was standing outside chewing nails trying to reinvent and rebuild the kit every time the sky promised to be clear and then wasting half the night trying to put a subject anywhere near the sensor. I was making short subs and expecting 50% of my frames to be useless owing to poor tracking. Sometimes I managed to get some version of auto-guiding working, but it hardly mattered: the end results weren't much better. That does not resemble my current routine.

Now the imaging tools are controlled by a computer that I, in turn, control from my desk. These days, there is one power switch and one USB connection between thinking about imaging and imaging. I expect every single sub-exposure, whether 30 seconds or 30 minutes long, to be guided and focussed well. The kit is no longer carried outside, set up and torn down every clear night; it lives in the backyard semi-permanently under an excellent cover (the camera / guider comes inside in an airtight Pelican case if extended damp is forecast). The decision to image used to mean 2 hours of work before I could start taking data and then hoping for the best. Now, I expect success every time I open the shutter.

The game has changed that much. But what belongs here? Nobody learns from their successess. Likewise, visiting the websites of photographers who have it going can be enjoyable and even inspiring, but this 'blog has always been about mistakes and their eventual fixes (with incremental successes salted in for color and relief). Surely it still will be. A talk by Johnny Horne at Kingsport, Tennessee's, Bays Mountain Planetarium convinced me just how valuable that could be. So I'll leave those painful notes leading to today's state of affairs (which may seem awful in a year two, also) where they can be perused and hope in the new year to collect even more productive mistakes and even more impressive photos.

In the meantime, it's time to decide how the slowblog should reflect this new level of the game.


12/17/2011. Also in the meantime, the sky is clear, although the western edge of a 120 to 160 mph jetstream is right overhead scrambling seeing into the god-awful regime (3 arcseconds or worse).

First, I rehearsed and rehashed polar alignment using the PHD assisted routines detailed here last week. Round stars seem to suggest I am getting the hang of that though it still takes on the long side of half an hour to get it done. With more practice, I'm pretty sure that can become a 10 minute process.

Cable management seems to be a renewed issue in early winter (42F at sunset dropping to 25F). After shooting these frames, I rearranged the cables some to see if I can keep the telescope from "picking up" the heavy, increasingly stiff bundle as it drops through about 55-60 degrees above the horizon. The relatively quick changes in forces on the 'scope produce some exciting moments for PHD Guide. At least I think that's what's happening. Our flying squirrels might be carroming off the tube for all I know.

I ran the 'scope from zenith to rooftop a few times at 600x sidereal rate while watching where slack went, how the cable fed into the motion, when one or another wire seemed too close to taut. (And why have I only gotten around to this now? Good question.) Then I added more slack between the florists' wire that holds the bundle to the telescope cradle and added a bungee on the pier to take up the weight and potential tension from the lowest lengths of wire where the cable feeds from various power supplies and adapters into the bundle.


m33 ha

M33, Hydrogen-alpha sweetened
2x1800s Ha, 6x900s L, 1x900s RGB
(I applied noise reduction to each channel seperately, which greatly
helped detail. I'm not sure where the "grain" is
coming from, but more exposure is usually the cure.)




M1, the Crab Nebula
13x900s H-a




NGC 7331 and the Deer Lick Group
(named by Tomm Lorenzin for an overlook near milepost 337
on the Blue Ridge Parkway, 38 miles due west of here) 12x900s L


See? That's the way telescopes are supposed to track. CCD Inspector still detects field rotation (via its aspect map). Taking 12 good 900s integrations while we watched Get Low is a nice way to spend a chilly evening. Some RGB would be nice, but there's no time for that tonight. I moved on to M33 just as it started down from the zenith. Had some good stuff happening until clouds moved in. The guider is hanging in through thickening murk (RMS 0.50 pixels = 0.4") which is doubly impressive considering the dreadful S/N I'm seeing on the guide window. I'm going to shoot some fresh flats (used in the images shown here), then maybe a few darks while I read more of Walter Isaacson's bio of Steve Jobs. The IR satellite says this might be just a fast-moving bit of fluff, but it feels like the night is done. (Speaking of fast-moving fluff: worth considering that NGC 7331 there is a little bigger than the Milky Way and is moving away at about 500 miles per second; it was six million miles farther away at the end of tonight's portrait session than it was at the beginning.)



3x900s L + color data from yesterday's images
(PSF's are typically 2.3 compared to 3.3 yesterday)



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. A Meade DSI Pro monochrome camera looking through a modified Orion off-axis guider keeps the OTA pointed in the right direction. The imaging camera is controlled via Nebulosity 2; the guide camera is operated by PHD Guide 1.13, both by Stark Labs. The stock focuser on the AT10RC has been augmented with Robofocus 3.0.9 using adapters turned on the lathe downstairs. Maxim DL5.12 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.


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                   © 2011, David Cortner