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Old 23-11-2014, 09:22 PM
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Shiraz (Ray)
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Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,822
Hi Barry. As first supplied the focal plane was a little bit out of plumb and needed slight tweaking. After the Peltier was replaced it was a long way out and I spent about 4 hours making up a jig and re-aligning it with a laser using the adjusting screws on the camera. The effects of the misalignment were dire - star shapes and sizes varied over the field of view. I think that, with a CC, image plane tilt can lead to under-correction of coma on one side of an image grading to over-correction on the other, as well as varying stars sizes due to focus shift. The adjustment mechanism on the SX is just good enough to get everything aligned to the required 20 or so microns, but the opposing screws are fairly small and the alignment can move if the camera is bumped at all - I presume that the Al housing threads give slightly.

Last edited by Shiraz; 23-11-2014 at 09:45 PM.
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