|
David,
I expect that using the AP rings on your Traveller
will help avoid flexure. I have a different set-up than you, but I found
that the felt lining in the rings can allow flexure as the mount moves through
RA at 15° per hour. To solve my case, I removed the felt and relined the
rings with a hard paper (I used automotive gasket material about .020"
thick). I was getting oblong stars in 45 minutes to an hour with the felt,
and was able to shoot for 90 minutes after replacing with paper. I
replaced the felt on both my main scope (AP 180/f9) and the guide scope (Tak
FSQ106 that weighs 14 lbs).
It only takes a flexure of 2 or 3 arc seconds to
show up in a photograph, which is 0.00015 inch on one ring 10 inches
away from a rigid ring.
I rarely use my set-up as a guide scope. I
generally use either scope with an off-axis guider to avoid these
problems.
Don
|