Guide scope v Off axis guider

[Carl]

Hi folks
I have on loan a celestron off axis guider and I am buggered if I can see anything thru it let alone a guide star. No matter what I do I just cant seem to get it to work. On the other hand a bloke found in the rubbish a 70mm apeture 700mm focal length refractor. I put in my 1' to 1 1/4 adapter added my illuminated reticle and bingo I can see.
So what should I do mount the guide scope on to my C8 or persist with th OAG. will i get much in the way of flexure on a 700mm scope mounted on a Schmidt Cassegrain C8?

Please advise needed as I'm trying to get into deep sky imaging.

equipment: celestron C8 on CG5 mount.
Permanant peir in Observatory
Imaging using f6.3 focal reducer and canon eos350
Capturing with DSLRfocus

[allan gould]

You have the right photographic setup ie C8, f6.3 focal reducer and guidescope but I doubt that the cg5 mount will be capable of guiding due to gear backlash for the image size of Canon 350. I hope I am wrong but I doubt it.
Flames welcome (but with photos to back it up)

[Striker (Tony)]

Normaly I would agree with Allan but it has been shown by a few members such as frank who is autoguiding the CG5 with SCT for over 10 minutes with great results.

http://www.iceinspace.com.au/forum/s...ad.php?t=14484

[[1ponders] (Paul)]

The other thing to consider with the SCT/Guidescope combo is mirror shift. With an OAG that can be taken into consideration, with the guidescope you will loose that image 'cos the guidescope won't detect any shift.

Having said that, I have an OAG that I never use cause it's a pita to try to find a suitable star to guide on, so I use a guidescope. BUT the meades do have a mirror lock to help reduce the likelihood of mirror shift/flop.

[Lee]

I went through this not long ago, I'm planning on picking up a cheap 70x700..... see this link

[Striker (Tony)]

The concern I have over cheap refractors as a guide scope are there focuser.

I had a skywatcher 70mm 900mm fl scope I trialed as a guide scope..it was awful and virtualy unuseable as a guide scope due to its cheap plastic R&P focuser.