I have been pretty happy with my setup for deep sky objects:
Orion EON 130mm ED Triplet Refractor / Orion EON 3" field flattener / ZWO Mini EFW with Astrodon Filters / ASI1600MM-Cool Camera
But for very bright stars, I always see a distinct symmetric pattern around them. Attached is an example, cropped of a Pleiades star from a 5 second blue filter sub. Of course, the pattern is much more obvious in the integrated master.
What is your view on what is causing this? I assume it is the CMOS window or the flattener.
Is there any way to prevent it (aside from not imaging bright stars)?
Edited by Gary Imm, 07 November 2016 - 10:13 AM.