Quote:
Originally Posted by Atmos
I've never done any real panos so I don't have any experience with it but consider the distance. The parallax of our nearest star can be done in the back yard over a 6 month period as we have the Earths orbit as a baseline. Having two telescopes let's say, one metre apart, does not have the resolution to be able to detect parallax. If it did, any star in our stellar neighbourhood would not be registerable from one minute to the next due to its movement due to the Earths orbit and close stars moving against the stagnant background.
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Yeah you are most likely right there.
Best guess is PA is off if the guiding is good but there is drift, that is the usual culprit, 2nd guess would be differential flexure which is hard to handle. Differential flexure raises its ugly head in a simple camera on the focuser all by itself without a tandem bar, a 2nd set of rings, a second focuser, a 2nd guide camera mounting, pickup prism. Also how square is the pick up prism for that matter. They are merely glued onto a metal frame so not 100% orthogonal anyway.
Also guide stars with OAG often show distorted stars to some degree off axis as scopes generally have poorer performance the further away from the centre the star is.
3rd guess would be differences in curvature of the optics and focal length causing some interplay that is not ideal.
You'd have to eliminate each of the above with some tests. A fresh Tpoint model to check PA accuracy for starters. Flex is harder to measure but if you got round stars on the scope the OAG is on and not on the other there is your answer, its flex.
Another simple approach is to use PHD2 or Pempro to do Polar drift alignment and you can adjust the drift out in real time until its stable and then it does not matter what was causing it unless the flex is worse at different angles that is!
Greg.