Quote:
Originally Posted by Joshua Bunn
A focus shift with the hedrick focuser or the rotor focuser? These things have lead screws (as you know), what are you observing?
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I suspect its the Aspen 10 position filter wheel. The front and back plates on that are ridiculously floppy. I was worried when I first took it out of the box. I might be able to stiffen the arrangement with some external struts.
I'm seeing about a 250 micron change in position beween zenith and 60 deg south. The sweet spot on the CDK20 is very generous and it barely affects the central stars, but the corners on the full frame chip start looking pretty dodgy unless I refocus. Luckily it can be done automatically under scripted control.