Quote:
Originally Posted by OzStarGazer
Sorry if this is a basic question, and I don't want to hijack Ian's thread, but I was just wondering what the advantages of a webcam over prime focus would be? Of course it depends on the webcam and the DSLR camera, but in general...?
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A webcam-based planetary camera is cheap and light, and just fits straight into the focuser like a normal eyepiece, but it is not very sensitive so it is limited to bright "planetary" targets. Individual exposures are short, but you can stack the frames from a video to make a better quality composite image. (An unmodified webcam with its original lens can be used for afocal photography through a standard eyepiece, just as you can shoot with pocket digital camera or smartphone, but a webcam-based "digital eyepiece" for a telescope has no lens and is used with the sensor at "prime focus".)
Dedicated astronomical CCD cameras work in much the same way, but have sensor cooling and different (more expensive!) hardware to allow for direct long-exposure shooting onto the sensor.
Using a DSLR at prime focus is much bigger and heavier than a webcam-based camera, so it demands more overall rigidity in the mount and focuser than you can get away with a webcam, and may also require some adjustment to your telescope's counterweights to compensate for all that weight hanging off the focuser, but it allows you to use the bigger sensor, longer exposures, higher ISO sensitivity, etc that the DSLR permits.
