In my last M57 image taken with the 130PDS, there is a strong ghost reflection diffraction spike in the lower right area. There are a few more, but they are mainly ultra faint and only visible in 100% resolution. So far I could not explain what causes them.
Yesterday I did M57 again, but with the DSLR 90° rotated to see any difference in the reflections. I did only 12 exposures. No flats, darks or bias.
At first glance no reflections were visible in yesterday’s image. But there is also a reflection in the lower mid left area.
If I check the field around my field of view in Stellarium I see a bright star on the reflection opposite side.
Both stars (Solafat and Sheliak) are around mag 3.5. So I think these reflections must be caused by bright stars outside the field of view.
So far, I’ve no other explanation for it.
The big question is how to prevent these reflections… maybe darken the inner tube and the spider vanes…
Michael explains the reason for these reflections in his comment below. Thanks a lot for this!
The reflections are caused by bright stars that are outside of the DSLR’s field of view (red), but within the telescope’s field of view (green):