Thank you for your reply, Paul.? Also, I appreciate the link to Mark Crossley's webpage.
?
For the "non-integer gear reduction" I referred to, I meant the non-integer reductions between the individual gears, as Mark Crossley mentions in his webpage. As I understand it, the MI-250 was built with Losmandy motors and gear boxes.? I know my MI-250 has a current Losmandy motor for RA, and the gear boxes look very Losmandy-like.
?
I've read various accounts of misaligned worm blocks in Losmandy mounts built prior to the the OPW (my G11 is from 1999 and has separate worm blocks).? The worm bearing housing in my MI-250 is "in between" the original Losmandy design and the OPW design: the in-board and out-board beaning housings are bolted to a common piece of stock.? Variation in alignment of the worm bearings when everything is disassembled and reassembled should be minimal.? However, there is the possibility the three pieces aren't machined exactly square and parallel, thus introducing misalignment and the "pinch" Mark Crossley refers to.? Perhaps another similarity between the G11 and MI-250.? I understand your comment about PEC not being able to correct for the "76 second error".
I also remember all the discussions about the "76 second error", that was long before I was interested in photography and if my G11 has it, it didn't bother me at the eye piece.
?
Thank you for confirming the "2x worm cycle" is a feature in Gemini II.??
?
I understand that worm phase shifting between sessions is a separate issue from gear boxes, worm bearing block alignment and linear drift.
?
Since you bring up linear drift: I've seen a few posts about that.? None of the posts I've read mentioned if the drift manifested itself over several sub-frames or during a single frame; and in either case, how long it took for the drift to become noticeable.? Does the linear drift manifest itself as oblong stars, or does it take long enough it manifests itself as the target object slowly drifting off-center?? Something else?
