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Old 24-07-2018, 07:07 AM
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PRejto (Peter)
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
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Hello Eric,


This is a very clever way of separating the two sources of error!!


The problem as I see it is that the TEC focuser (which would allow me to mount the camera system independently of the rotator) uses the same type of adapter and isn't accurate either. This would matter because I would be shimming to fix the focuser error, no?


As for "b" in the previous post, I will supply those numbers soon.


Just to clarify, are you suggesting that I do the first step without the flattener (i.e., mounting camera on TEC180 without rotator) so that the defocus to edges is more apparent and provides an easier target to find the optical center? Currently I don't have adapters that will allow me to put the camera on without the flattener. But, even so, the stock focuser is as big a problem as the Gemini!


As far as roughing out the optical center, might I use a flat frame to get there? I would look for symmetrical darkening in the corners. And the beauty of this is I could do in during the day and in relative warmth not to mention light. Doing any of this in darkness at -2 is daunting and maddeningly hard.


Peter




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Would it be a mistake to consider having an adapter made that directly uses the threads on the TEC180 to which the locking collar fits? Yes, there would be no auto-centering by fitting 2 conical parts together, and the accuracy would be entirely based on how accurate the machining was done manufacturing the adapter. However, it would be repeatable and that would make shimming much easier.



Many thanks,


Peter
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