My ZWO Ha and S2 filters are producing flats which have some sort of ring. L, R, G, B are OK. O3 filter has some sort of pattern. But I am mostly interested in Ha and S2 flats having this bright ring.
The telescope stuff:
Televue 102, 0.8 focal reducer, ZWO OAG, ZWO filter wheel, ASI1600Mono, LED light panel for flats.
Here is the attached image - L flat and Ha flat stretched to same values using Pixinsight.
It seems like I need to buy better filters if someone cannot come up a with a solution for me.
There is extensive discussion on CloudyNights:
https://www.cloudynights.com/topic/6053 ... lled-test/
https://www.cloudynights.com/topic/6005 ... artifacts/
I wonder if these apply to my experience.
New filters/filter wheels come with some sort of Filter Masks. When I purchased my set of filters and ZWO filter wheel, they did not.
Will it be possible for ZWO to ship me the filter masks? My filter wheel is 36mm filter wheel with 36mm filters.
I will report if filter masks solve the problem.
I saw another thread that ZWO has newer version of the Ha/S2 filters. But it will be too much for me to replace my first-gen ones - I cannot afford new ones. Hopefully, $15 fixes the problem.