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Old 21-10-2018, 12:15 AM
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astronobob (Bob)
Casual Cosmos Capturer

astronobob is offline
Join Date: Jun 2010
Location: Gold Coast SE QLD
Posts: 3,866
Originally Posted by gb44 View Post
Hey Bob

Astigmatism is clearly there when you look at the difference between 1 & 7 and between 2 & 8 out of focus images. There is the 90 degree difference in the light pattern.

The star field shows a uniform star shape distortion. If it aint tracking error then maybe some tilt in the focusser / imaging train.
I have seen this star shape when using the old Meade DSI and I attributed it to oblong pixels! ZWO say their pixels are 2.9 x 2.9micron so that shouldnt be the cause - anyone else seeing this with the same camera?

miscollimation could cause that flared focussed star image. Final collimation visually at high mags should help there

No sign of coma there IMO.

Interesting, thanx Glenn,, a combination of capers going on here nbo me thinks,, bit of everything

This scope is now resting with the Primary having no mounting clip pressure holding the mirror, could be a fact of possibly being to much torque on these causing astigmatism ?

I will also check the focus tube mounting alignment for squareness in relation to the tube, this & other collimating issues may/most likely have been attributing to these poor star shapes inside & outside of focus...

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