Using the standard video modes won't be all that useful as the FOV will be too great. However you can capture the zoomed in liveview stream from cannon DSLRs (no idea about Nikon) using backyard EOS. Another way to capture the liveview is to use a program called "extrawebcam" which turns the camera into a webcam, then you can use sharpcap or something to capture. That's on Windows but I'm sure there are similar applications for Mac.
See this thread for a Jupiter I captured with a canon 7D through my ed80+2x Barlow:
http://www.iceinspace.com.au/forum/s...d.php?t=102289