No skies so a little gear maintenance. The very best thing about borrowing the SCT was that it caused me to discover a problem I’ve experienced ever since upgrading to the 12″ RC from the 10″ version. I transferred my trusty old Moonlight focuser to complete the swap. I’ve had that focuser on any number of SCT and RC telescopes with great performance. I noticed right away that I had poor star shapes with the new RC, which I had purchased as a “scratch and dent” special due to a serious hit in transit to a trade show. I was sure it was a primary centering issue caused by the hit so I was looking forward to swapping a different OTA onto the mount so I could tear down the RC and sort that. Didn’t even think about focuser alignment because I had just been using it without issues.
WELL – there still might be a centering issue but I suspect not. When I transferred the focuser onto this SCT I discovered the same kind of centering/tilt symptoms! Turns out that when I transferred the focuser onto the 12″ RC it became misaligned (it had been perfect on the 10″). I don’t remember dropping it or anything, and collimation adjustments on the Moonlight are nice and beefy – but it happened somehow. I put the camera directly onto the telescope and all was well so that nailed it as a focuser issue. The internal focuser works very well, indeed, but I need remote focus to follow temperature changes so I stuck my old Meade Microfocuser on there and that worked fine also. I miss the stepper-driven Moonlight, though. Tonight I put it on the bench and found it to be way off. I adjusted it and got it very close. I may have to tune it up a little on a telescope but I’m in the neighborhood. I’ll stick it back on the LX850 OTA next time I’m out there and see what I see. Then, when I put the RC back in I’ll see how that does with a well-collimated focuser. I’ll bet it works properly for the first time ever.
It’s embarrassing to report such a misdiagnosis, especially when I’ve owned the 12″ for a couple of years and had plenty of opportunities to catch it! Still, a happy ending is a happy ending and there’s a good chance that this was the only issue with the RC.