I recently got the ASI1600MM to use with my Meade 70mm Quad f/5. On the ZWO website and in their manual, it states that the 1.25" filters are good for scopes up to f/5, yet I still have vignette with different gain settings and exposures. The vignette isn't so bad on the Ha filter, but in SII and OIII it's prominent even before stretching in post. I know that flats can fix this issue, but I was wondering if anyone else has had this issue? How did you fix the issue? What gain/exposures do you use for narrowband and LRGB? I've read that the back focus for this scope is 43mm. Anyone know anything?
My imaging train is Telescope>16.5mm extension>EFW>ASI1600MM
Any help will be extremely helpful.