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Odd Star Shapes with different filters
I have noticed some odd star shapes in quite a few of my subs lately. One interesting factor is that the effect seems to vary from filter to filter. Attached images are NB images of the South Pillars Area of Eta Car. Taken with an Edge HD 8" scope, ZWO ASI1600MM cam and Astrodon 36mm filters in a ZWO filter wheel. These are only crops of single subs that I have stretched so plenty of stars are visible. In order they are
SII Top Left (nice round stars)
Ha Top Left (really bad stars!!)
SII Centre (nice round stars)
Ha Centre (Not bad stars but still not good)
Any idea what may cause this? Only thing I can think of is that the filters are not sitting flush in the carousel. If wit was tilt or collimation, it would surely show up in all images?
Malcolm
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