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Taking Images (part 2)

Initial Thoughts Second Thoughts More Thoughts

Second Thoughts

Setting Up

I have been using my ETX with the AutoStar in polar mode recently for taking pictures of dim fuzzy objects because it really is nice just to be able to hit "GOTO" and have it find them. I have noticed, though, that even in polar mode it just doesn't drive the telescope very steadily. It tracks very well and an object will remain in the frame for an awfully long time, but it seems to buzz and jerk and high resolution details (like the Cassini division) tend to disappear while it's running. For this reason I've taken to not using the AutoStar at all when photographing or viewing planets, instead simply using the paddle that came with the ETX.

Capture Software

As it turns out, I was under the mistaken impression that the Video For Windows API didn't support 24-bit images. It does, and any software that uses it can potentially support 24-bit captures. I have written a simple capture program that does just the things that I want it to, and may release it if I get it stable enough.

After playing with the various QuickCam settings and examining the histograms of the images that result, I've stopped leaving all of the sliders on 128, and now use the color sliders to try to even out the color balance of the image that comes from the camera, compensating for the enormous blue excess that came with removing the IR filter. Also, the "white level" slider seems to multiply all of the pixels by a fixed amount, and so stretches out the dynamic range a bit. I've taken to setting it higher and reducing the exposure (brightness slider) a bit.

Dim Objects

The capture software that I now use allows me to both subtract a dark frame and multiply the result by a constant, which makes it possible to see dim stars and other objects directly on the screen. I don't have to use that screwy GOTO technique to center them anymore.

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