Hi,
Sorry for the silly questions but I am trying to find out what the correct back focus should be for a Sky-watcher 72ed, I have searched high and low on the internet for a manual thinking this would tell me. I have a few CCD's but these have been used for planets using a CPC925, I have got a skyris 618m, ASI224mc, Alatir GPcam and a Alatir GPCAM 2 mono for guiding.
I would like to try my 72ED with a ASI224MC and try some DSO imaging, when I tried to focus with the ASI I could not achieve focus.
1) Do I need a 50mm 2" extension for a DSLR and a 80mm 2" extension tube for a CCD.
2) Do I need a field flattener and a smaller extension tube if the flattener is used?
3) What would be a good CCD for imaging with a 72ed refractor?
Any help or advice would be great
Many thanks
Craig