I am seeing an unusual pattern on all my images taken with a ES 127 ED Apo
My equipment is as follows:
- ES 127 ED Apo
- Moonlite Focuser
- ES .7x reducer/flattener
- ZWO filter wheel (8 filters)
- ZWO ASI 1600mm Pro
I have exactly 55mm of distance from the reducer to the camera sensor. I am able to achieve focus just fine, but all my images have a giant ring around them as visible in images and flats. Here are examples:
Flat frame taken using an R filter.
90 second Light frame of Sombrero Galaxy using R filter.
At first I thought it was because I am using 1.25" filters instead of 31mm, but if I remove the filter wheel from the equation, the problem is still there. I have noticed as I decrease the distance from my camera sensor to the focal reducer, the ring begins to increase in diameter essentially pushing it further out of the frame and reducing the problem. If I increase the distance, the ring diameter shrinks and the ring moves closer towards the center of the image. I have yet to try to achieve focus (haven't had a clear night in a while) with the camera closer to the reducer but I am expecting to have issues here since the product's back focus is 55mm.
I can use flats to get most of the ring out of the way, but this pattern seems unusual to me and I have seen un-processed photos of very similar imaging platforms (same telescope, camera and reducer) in same light polluted skies and do not see this pattern. I am out of ideas on how to fix this issue or if it is even fixable. Maybe there is something wrong with the reducer/flattener or maybe I should just move the camera closer than 55mm and hope I can achieve focus still. I am curious if anyone else has run into anything like this. Any help is greatly appreciated.