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How I am fighting differential flexure!

Differential flexure can occur when one part of the imaging system shifts slightly such as when a focuser (either on the guide scope or imaging scope) sags. The goal to beat this is to 1) use an Off Axis Guider or 2) make sure all parts of the guide scope (including camera) and imaging scope (with camera) is as rigid as possible and "moves" as a complete unit.
I added tube rings to the focuser and one on the autoguider to limit flexure at the focuser on the 80mm Short tube. So far so good, I was finally able to guide 6 min subs with the AT8RC (FL 1625mm) the other night.
Click here to see images of my current set up.

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Comment by Fredrich Clarkson on December 7, 2014 at 1:33pm

How are you attaching the ST80? I can't see any rings. I love the set up, though! What size are the rear rings? I have a similar set up without the rear rings and I suffer from flexure to point where I'm ready to give up.


Comment by Steve Coates on March 9, 2013 at 6:32pm

The Moonlight is much more solid than the stock focuser. I cannot compare it to a FeatherTouch because I've never handled a FT before.
I am hoping to use this set up and I hope that it holds well keeping flexure at bay. I do admit though, I have the QSI upgrade on my wish list if this set up fails...

Comment by Greg Marshall on March 9, 2013 at 3:09pm

Steve, I had a similar setup and it worked well for a while, but symptoms of differential flexure started showing up again. I tried everything I could think of to eliminate it, but finally gave up and went to OAG (upgrading the QSI camera to the 'g' suffix). This was expensive and I find OAG a pain in the butt to use, but it did solve the problem. And as a bonus, it reduced the system weight quite a bit.

In retrospect, I believe that it was my focuser that caused the problem. That is, I think it would tilt very slightly with gravity. So I'm thinking of upgrading to a better focuser. I prefer FeatherTouch, but Moonlite has an adapter in stock for my scope. So how do you like your Moonlite? Does it feel really solid?


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