Front Page


The Old Set of AstroDon Gen I Filters Suspected to Lead to Degraded Images


Further Test by Rotating the Filters 180deg



The Resulted Null Flat (On Left side) Remains as Smooth (albeit a little cleaner after further cleaning the CCD Chamber Window)


Resulted Luminance Flats (on Left Side) Vs Original



Resulted Red Flats (on Left Side) Vs Original


Resulted Green Flats (on Left Side) Vs Original


Resulted Blue Flats (on Left Side) Vs Original


Observation :

The shifts in uneven illumination patterns along with the rotated filters are clearly discernible. These shifts would have been even more obvious if not masked by the superimposed general light gradient perhaps due to an imperfect light shield, twilight gradient, etc.


Other Filters for Comparison

Baader Ha Flat


Baader SII Flat


Baader OIII Flat



1. There are no central hot spots in the Narrowbands flats.

2. The illumination patterns are smoother and there are no uneven illumination patterns so obvious in the LRGB filters.


A Discovery

A possible Crack (in the substrate?) of the Luminance Filter (position 1): the white dot (with its reflection) on one side