|
Guide scopes are a little old fashioned really. They are prone to differential flexure when either of the scopes flexes differently to the other causing elongated stars.
OAG are the modern solution. There are several these days and several cameras now have them built in like QSI and QHY and Atik.
If you do use a guide scope I would go longer than a finder ideally. I suppose you can get away with it if the guide camera has small pixels but ideally it should be longer and very rigid.
If its too long then it can be harder to find a guide star but at 500-600mm that shouldn't be a problem anyway.
I also find the SBIG STi guide camera the best I have used as it can do autodarks. Some guide cameras have artifacts that are hard to dark subtract out as you then need a library dark that the software will use to auto dark the image and some softwares don't have that facility. The STi has a shutter which means it does one automatically when set to do autodark on its first exposure.
Try to get rid of guide scopes from your setup.
Also try to work towards using software to get your polar alignment really spot on. The Sky X and TPoint works incredibly well for that. Its a bit to master it but once you know it you can get perfect Polar Alignment in less than half an hour.
There goes most of your tracking problems.
Greg.
|