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Hi Carl, ditto to Tony's info, plus for your flat frames you image a flat light coloured evenly illuminated wall or similar. These should be long enought to show any vignetting. I find if I select my ISO and then allow the camera to automatically adjust for exposure etc they turn out ok.
The really really really important thing here is, you have to leave your camera attached to your telescope to take flats. Don't move it, rotate it, adjust focus, anything. When you take a flat you are trying to get an image of your systems optical "faults" like vignetting, dust on your chip, the "shape" of optical light path etc and this will change with changes in camera orientation and focus. So don't adjust anything. I usually leave taking my flats til the last thing when I take my scope inside. I set it up on a table, pointing at a wall about 600mm away from the scope. The wall needs to be very evenly illumninated otherwise you will get false flats. Just one light coming down from above will give a poor flat. There is a good article by Eddie_T in the Resources section on the how and why of taking flats.
When it comes to taking darks, as long as your temperature hasn't fluctuated more than 2 or 3 degrees during a session you can take your darks with the camera off the scope and just the lens and cap on when you are tidying up. BUT only do this if you have already taken your flats and the temperature hasn't changed, otherwise take them during your imaging session after your lights as Tony suggests with a cover over the end of your scope.
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