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Originally Posted by g__day
"Auto guiding can be done with a seperate telescope piggybacked onto a larger one and a CCD that picks a pixels and keeps your star there, but more recently this can be done with newer CCDs that stack and autoguide (interleveling between the two 10 - 100 times a second).
So you tyoically do segments of 10 - 100 exposures of length 5-10 seconds during each exposure the CCD is flipping between recording all pixels and then next round monitoring a target one to keep a guide star in view"
Gives you more options!
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This is all true g_day, there is one downside I can think of though and that is that it will take you twice as long to take each image. So a 5 minute image becomes a 10 minute image.
That in itself mightn't be too bad but will this now increase the amount of noise in your image (because you are effectively taking a ten minute image) or not? I don't know but I have a feeling that it will. If so then any darks you take will have to be 10 minutes long as well, thereby doubling your dark capture time as well. so a normal 10 minute shot then becomes 20 minutes. Ok not so bad until you start looking at taking what would normally be an hour of 5 minute shots (12 shots). goes from 120 min to 240 min.
I think the Starlight Express range work as you are describing and there are many people using them and singing there praises as a very good imaging/guiding tool. Unfortunately there is a trade off.
M2CW in case you weren't aware of it.