Is anyone having an issue with moonlight bypassing the ZWO 7nm 31mm narrowband filters and getting onto the asi 1600mm pro sensor?
My imaging train: ASI 1600mm Pro > ZWO 5 pos electric FW > 21mm spacer > TS 16mm OAG> 0,79x flattener reducer>focuser>telescope
I just recently switched to using 31mm NB filters from ZWO. Before I was using the 2inch 12nm Astronomik Ha filter that I screwed directly into the flattener and it worked great with no stray moon light effecting the image quality.
Because I have the 5 pos FW I can only mount 5 filters so I temp. replaced the green and blue with OIII and SII so my filter wheel looks like this ( L,R,Ha,SII,OIII).
So that's that. I have been testing the filters for the past 2 nights and realized that the moonlight, even at only ~50 illumination has found its way into my camera sensor. I have checked the time where my frames are starting to get brighter and brighter and it matched with the moon rising above horizon.
So i'm confused now. Isn't the idea of narrowband filters to image during moon light and in light polluted cities? in a bortle 4 zone and with a 55% illuminated moon the 300seconds frames are quite washed out, I can't even imagine during the full moon or inside a city, the image would be completely washed out.
before moon rise:
after moon rise:
I was also looking at vignetting to identify the source of light leakage but the thing is that the whole frame is evenly illuminated. Flat frames look decent enough with minimal reflections. I also used a flashlight to shine down the telescope tube to locate the source but nothing obvious was found. And the air gap between the camera frontal plate / window and the filter surface is <1mm. So how come there is so much moon light in my frames? Is it maybe passing trough the luminance filter that sits next to the OIII filter, but wouldn't a lot of people have the same issue?