Re: AP900 Gto Auto-Guiding woes.
The only scope I have ever owned that didn't suffer from differential flexure between a piggyback guide scope and the main scope is my AP 130EDF-GT. That is why I ONLY use off-axis/radial guiders any more.
Over in the Meade Yahoo groups that I haunt (I also have a 16" LX200GPS) I am constantly amazed over how many scope setups I see where there is an under-mounted SCT combined with a small Chinese refractor and a floppy focuser riding on its back. And not an OTA counterweight anywhere in sight.
Of course I rarely see any images taken with those scopes...
Waikoloa, HI 96738
From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, October 14, 2016 8:44 AM
Subject: Re: [ap-gto] Re: AP900 Gto Auto-Guiding woes.
Vince, you want the guide scope/camera to be fixed relative to the back of your imaging scope. Ideally mounted on the focuser but with your scope that seems impractical. You could try a second pair of rings that are lower profile around the big tube and move them back as far as possible.
What is the focal length of your imaging scope? AP makes a very elegant guider holder that mounts on the focuser. I'd talk to them about that vs. what you're trying in the photo if that set-up is suffering from flexure.
BTW - I imaged for years with a 350mm focal length Borg 60mm guide scope mounted to the top plate on my AP155. I was able to stabilize it fine and never had an oblong star in all the years I did that. You should be able to do what you're trying but it may need to be more securely attached than what I see in the photo. In my case, I had the guide camera, an ST-402ME, sitting firmly on the top plate of the cradle holding the AP155. The rear ring of the cradle nestled up against the focuser. The front of the Borg 60 was held in a Losmandy 3-point ring and the body of the Borg 60mm was held in a second Losmandy 3-point ring. The three points were tightened down really hard.
I'll try and get a photo of this set-up.