First image using a 0.7 FFFR that my wife gave me for Christmas. It's not designed for my scope (ED127) but Explore Scientific says it works well with it, using their adapter to convert from a 3" to a 2" focusing tube. I bought the adapter separately but was more than a little disappointed to find that it didn't have a threaded connection to the focuser tube. This gave me a few problems since ES's design expects you to use the non-threaded connections. No matter how hard I tightened up those three screws I could not stop the image train from flopping by about 2mm as measured at the camera end. The second problem was the backfocus. I very carefully set the back focus to 55mm per the spec for the FFFR, but you'll see that the stars in the corners are running away from the center of the image, which means that 55mm is too close. I'm going to have to experiment a bit to find what the backfocus should really be.
The good news is that this reducer converts my ED127 into a 666mm focal length scope with a focal ratio 5.24. With such a speed increase, I calculated that my optimal S/N ratio sub time would be around 90 seconds when using the ZWO DUO filter. So much less sub rejection especially on the second night which was very windy. Plus now I am under sampling (photographic resolution 2.95 pixels, sensor size 4.63 pixels) I used the drizzle integration process in PI - the results are amazing!
Anyway, disappointments aside, I went ahead and processed the image as best I could. I hope you like it.
Hopefully we'll have many clear nights in 2023
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