well, as long you temper your expectations, the CG5 can most certainly be used for astrophotography
here's one of the best imagers that I know of who uses this mount:
http://www.saratogaskies.com/
(though Jim seems to have acquired a Tak last week, most of his work is with the CG5- and an ED80 or an 8 inch newt)
and here are my own efforts-not quite in the same league:
http://www.flickr.com/photos/91784720@N00/
Narayan