From: "Tan Thiam Guan" <tgtan
Date: Sun, 9 Apr 2006 22:25:45 +0800
Date: Sun, 9 Apr 2006 22:25:45 +0800

Hi all,

I recently bought a Schuler V filter (2") from Adirondack.  In using the filter for the first time last night, with defocused stars, I noticed that the star images are not round (as they are with other filters I am using from Astronomik).  Star images are severely oblong, with the long axis switching direction depending on whether the telescope was inside focus, or outside.  I was using an 80mm refractor and CCD.


Questions:

1.  Does this sound like a problem with the quality of the filter? 
2.  Has anyone else encountered the same problem with Schuler filters?
3.  Will this affect the precision of photometry?
4.  Should I ask the vendor for a replacement?

TG Tan
Australia
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