MB 3/26/2006: Oh God, I'm an imager now

by Marek Cichanski

I've been thinking for some time about giving some basic unguided imaging a try. Since I have an EQ mount, and an ED80, and a 20D, I thought "what the heck?" A quick stop at Orion for a simple EOS T-ring, and I was all set. Ba-da-boom, ba-da-bing.

After last night's cloud-out, I watched the sky and the satellite loops all day, and my hopes were rewarded. So were the hopes of Dan Wright, with whom I shared the MB lot tonight. Dan and I managed to have some surprisingly nice conditions. There was some cirrus drifting past early in the evening, but most of the time we had almost completely clear skies, with pretty decent transparency and seeing. It was dewy, and chilly, but almost perfectly still, so we hardly noticed the temperature. For a chilly, humid night, it was quite warm - if that makes any sense.

My one previous foray into imaging occurred almost exactly 20 years ago. During the 1986 apparition of Comet Halley, I made a barn-door mount and drove to a dark-ish site with a friend to take a picture of the comet. I used some sort of Kodachrome in a Nikon FM, and took a 1-minute exposure, I think. Much to my amazement, the slide actually showed the comet, and even the Lagoon and the Trifid! Very cool.

Cut to 20 years later... let's try this imaging stuff again. My setup was about as simple as it gets:

ED80 OTA Canon EOS 20D DSLR, bone-stock. Not modified, not a 20Da, or anything like that. Old-ish Celestron CG-5 GEM that I bought off some guy at a Hogue swap meet. Has dual-axis drives, but you can bet your sweet posterior that they weren't being used for any sort of guiding tonight. This was as brain-dead of a mount as you could ask for.

So, I got to MB about an hour before sunset, to give myself plenty of time to get set up. No rush, no fuss, no muss. I just carefully set everything up, ready to shoot flats after sunset. (I barely even have any idea what 'flats' are, since I only asked Richard Crisp what they were about 24 hours previously. God only knows if I shot them correctly. My 'dark frames' consisted of putting my black fleece beanie over the end of the scope and shooting.)

I did a number of "K.I.S.S." things that helped the night go smoothly. Luck probably also played a role, too:

1) I lined up the 9x50 finder scope carefully on a distant ridgeline, so that I could just use the finder to put DSOs in the camera's FOV. Once the camera went on in place of the diagonal, it didn't come off. 2) I picked targets that I could see in the finder scope. Actually, come to think of it, that's not true. I shot NGC 4565, which I had to find using the finder and TheSky. When I captured an image, lo and behold there it was. Having racked up a hefty visual-observing body count came in mighty handy here. 3) I just focused by looking through the camera's viewfinder. No DSLR Focus, yet. Just point, squint throught the viewfinder, and focus. Given that this low-tech approach allowed me to resolve stars in M3, I'm calling it a success. 4) My only polar alignment was using the cheesy little boresight scope in the mount's polar axis. Its aperture is scarcely more than that of the human eye, but apparently it's lined up pretty well with the axis. I was blown away at how little drift is apparent in any of the images. Looks like I got lucky.

While there was still twilight in the sky, I pointed the scope at the sword of Orion. Dan was showing some late-departing hikers the sky through his LX200. The camera made that satisfying noise that an SLR makes when its mirror swings up, and then about a quarter or a half a minute later (I forget which), it clacked down. The camera did it's little high-ISO noise-subtraction routine, and the LCD screen lit up. It had stars! And this fuzzy thing! A second later, and the image had come down through the cable into the laptop. The sword of Orion! Wow! With the nebula and everything! I was amazed at how relatively non-trailed and round the stars were. Not perfect by any means, but better than I'd expected, and I think that some simple cropping will take out most of the worst offenders. The field was a lot flatter than I thought it would be.

I ended up going nuts, shooting all sorts of targets. Here's what I got data on last night:

• M42
• Pleiades
• M37
• M35
• M46
• M3
• NGC 4565

Here a few quick-and-dirty uploads of the raw images. (That's 'raw' in the colloquial sense. I didn't actually shoot "RAW"-format images. I mostly shot "large medium" jpegs.) These are straight out of the camera:

Here's the very first image - before I'd focused: http://nebula2.deanza.edu/~marek/images/astro/Image_0190.JPG

Here's the best-looking raw M42:
http://nebula2.deanza.edu/~marek/images/astro/m42.jpg

Here's an M3 that's full of sensor noise, light pollution, and which shows how small a gc looks at this image scale. But the fact that it shows as many resolved stars as it does is blowing my mind:
http://nebula2.deanza.edu/~marek/images/astro/m3.jpg

Here's an M35 that also shows NGC 2158, if you look closely:
http://nebula2.deanza.edu/~marek/images/astro/m35.jpg

I shot 10-15 images of each target, mostly 20-second exposures. I have no idea if I'll get any improvement by using Registax, but I'm going to give it a try on Monday evening or Tuesday. I can't wait to see what I can get out of this data... just as soon as I learn the very first thing about image processing. Hello, learning curve.

Well, off to bed, gotta get though tomorrow at work and then I can start playing with my images.

Tonight rocked - it was one of the most fun nights of astronomy in a long time. Oh, I'm not going to give up visual observing, not by a long shot. But being able to shoot some of the bigger, brighter objects so easily was a total hoot. It was a complete blast. When I got that first M42 image, and saw that it worked, it was one of those moments when you get a big 'ol grin on your face and say "No... fuggin'... way!" Red-lining the fun meter, I was. And I even had a big pile of battery packs under my tripod, with inverters and wall bricks and red lights and green lights, and cords and cables running to the scope. It was positively Crisp-a-delic! Terzian-esque! Santagel-acious! Cool! I noticed that I found myself doing the same stuff I've seen Richard doing, like wiping the dew off of the red laptop screen, and lifting up the screen to take the image straight. (Gotta do that from time to time, it turns out.)

(Oh, and you new folks, you buy the plastic for those screens at TAP PLASTICS. Two words: Yellow Pages. Hie thee to TAP, not to the TAC list for this particular item. Sorry to be heavy, but it's kind of an obligation, now that I've mentioned red laptop screens.)

Other than this unfortunate mention of a Forbidden Thread Item, it's a blast to be able to report on an imaging session. Hopefully I'll have some decent products after a day or two. Now I gotta sleep.

Posted on sf-bay-tac Mar 27, 2006 06:49:02 PT
Converted by report.pm 1.4 Mar 27, 2006 20:51:09 PT