Mac Lab Report

Shooting Mars with a Scope and Webcam

- 2003.09.04

This is the best image of Mars I've taken. It was taken on Friday, August 29, at about 1 a.m. Pacific. The equipment and techniques I used were as follows, with references.

The camera was originally based on a QuickCam Express, but since that is a PC-only camera, I removed the guts and replaced them with the parts from a QuickCam 3000 (, which is cross platform. The camera mount consists basically of a small black project box with a 1-1/4" outside diameter tube attached to a hole in the box; the CCD chip lies in the bottom of the hole, surrounded by black electrical tape to absorb stray light.

The telescope I and a couple of friends, Ray Kuntz and Eric Chamberlain, used was a 10" Meade SCT, specifically an LX200 GPS, which is pretty fun to use. This telescope aligns itself, or nearly so. All you have to do is verify a couple of stars and, presto, you're in business.

Basically I centered Mars, then moved the image down in the field of view until it matched the relative position of the CCD in the tube, popped out the eyepiece, put in the camera, refocused, and started recording. There was a 2x barlow in the light path for this image.

MarsUsing IOxperts' QuickCam driver ( and BTV's image capture program ( I made short QuickTime movies in real time of the Red Planet. A sample frame from that movie appears on the right.

When doing this sort of observing, it is important to save your work frequently.

Finally, using a program called Keith's Image Stacker, I selected about 20 of the best frames from the movie, then nudged Marsthem around so they were lined up nearly in the same position. Then the software added the images together and produced a raw image not too different from the picture above. Watching the resulting video is very similar to looking directly through the eyepiece yourself. Keith's Image Stacker does all the thing one learns about in a course in astronomy on CCDs: dark frames, bias, etc.

I intend to register all the the shareware mentioned above soon, so I can run longer sessions without being interrupted by shareware notices.

Have fun!

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is a longtime Mac user. He was using digital sensors on Apple II computers in the 1980's and has networked computers in his classroom since before the internet existed. In 2006 he was selected at the California Computer Using Educator's teacher of the year. His students have used NASA space probes and regularly participate in piloting new materials for NASA. He is the author of two books and numerous articles and scientific papers. He currently teaches astronomy and physics in California, where he lives with his twin sons, Jony and Ben.< And there's still a Mac G3 in his classroom which finds occasional use.

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