So as you are all aware, the Asteria 204-8 R35 is not an apochromat, but it does suppress chromatic aberration pretty well. This image is M13 from Seoul, South Korea and so light pollution is horrible. I have an Astrodon 3nm Ha filter and currently working with a Baader 8.5nm OIII filter. I will eventually replace my current OIII with the Astrodon 3nm version and probably go for the 5nm versions of SII and NII.
Anyway, this image is some normal Luminance data (which is where the chromatic aberration is visible), Ha and OIII for the narrowband data. The stars would be much tighter if I had done just Ha+OIII+RGB and left out the Luminance. But I don't have RGB filters yet, so this is what we for now
Overall I'm happy with it considering it is in the middle of one of the largest cities in the world... but what I really want to do is get back out to a dark site and redo this with LRGB +Ha and OIII.
Istar Asteria 204-8 R35 Anastigmat Takahashi TSA-102S Takahashi Epsilon 130D Astrophysics Mach 1 Mount/Tripod Losmandy G11 with Gemini II QSI 6120wsg-5 with Astrodon 3nm Ha, OIII, SII and NIR-Lum filters
The light pollution is really bad... even worse than I originally thought. I have looked on updated light pollution maps and I can't find a worse place in the world than Seoul for light pollution. Even Tokyo seems to have a smaller light pollution foot print than Seoul. Anyway, I literally live in the middle of the city and therefore suffer the worst of it.
Oxygen III filters seem to be somewhat sensitive to light pollution. I have read in several articles / forums that getting the most narrow band version of OIII will really help clean up the OIII images. My OIII filter is the Baader 8.5nm version. I have not decided yet, but I might opt for the Astrodon 3nm version of it if my images seem to be less than what I hope they are. Unfortunately, not only is Seoul plagued with horrible light pollution, we are in the middle of monsoon season and so I rarely even see a clear sky. I think I will have to wait till Sept to get some good clear nights to image on.