Greg Hewgill (ghewgill) wrote,
Greg Hewgill

astrophotography is hard

I finally acquired a bunch of hardware I needed to hook up a camera to the back of my telescope. Here's a short list of some of the things I needed:

  • 3Com HomeConnect USB webcam (I already had one of these)
  • Adapter to attach the webcam to a 1.25" eyepiece receptacle (this replaces the tiny webcam lens and makes the whole telescope the lens)
  • Borrowed laptop from moonwick
  • 802.11b wireless networking stuff for laptop (ok, I didn't really need this, but it sure is nice)
  • Two 6V lantern batteries to power the equatorial mount (old ones I had from three years ago died)
  • Warm clothes and a hat because it's cold out there!

The webcam offers a resolution of 640x480 (it also claims 1280x960 but I don't think the CCD really has that many pixels). Since the CCD element is so small, the field of view through the telescope is quite narrow, but I haven't worked out exactly how many degrees it is yet. And although the 3Com webcam is supposed to have good low light performance, I sure was getting a whole lot of empty black frames.

The moon was still up when I started, so I first pointed the telescope at the moon to align things and adjust focus etc. The focus needs to be adjusted by pointing the telescope at a target and watching the laptop webcam preview display for the sharpest image. It's not possible to adjust focus with an eyepiece on the telescope because the optics are different, so it's a totally different focus setting. This is a lot of trial and error.

To make a long story shorter, I fumbled around with webcam settings a lot and wasn't able to get anything anywhere near as sharp as the moon pictures I took with my digital camera. This was a bit disappointing but I'm sure I can figure out what I need to do to make this work.

I also tried Mars, which turned out as a roundish blob on the display. I tried the Pleiades, and found that the field of view of the webcam was far too narrow to capture the whole cluster. I tried the Andromeda Galaxy but although I could easily see it through the telescope, the webcam didn't show anything except a black field.

I think I need to figure out how to set the webcam for an exposure longer than 1/4 second. I also need an eyepiece with a narrower field to assist with centering the target in the field of view. Or maybe an illumiated reticle eyepiece which shows visible crosshairs in the field. I need better image handling software that can capture sequences of individual frames rather than having to click five or six times to save each image. I need a copy of The New CCD Astronomy which is apparently the best book on the subject.

Some things I've learned:
  • My backyard is not dark.
  • My back porch (second story wooden deck) is not a stable photography platform. The image jiggles like a bowl of jello if I walk around.
  • Focusing is harder than it sounds, especially when you can't really see what you're looking at.
  • Almost all stars look the same, especially when you can only see one or two of them at a time.

I will figure this stuff out. It will take some learning and practice, but I've seen good pictures taken with inexpensive webcams, and I know I can do the same.
Tags: astrophotography

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