I don't believe my imaging setup is all that bad, but I do wish it to be best if I can by making a spacer adjustment
See this picture I took and plate solved....
I have a 9.25 SCT and a 6.3 focal reducer. I computed a focal length of 1481.
Regarding the above picture data sizes/FOV, and the formula
Focal Length = 57.3 / (Field of View in degrees / sensor size in mm)
I compute a focal length of 1377 based on my solved image. I am using a ZWO 1600 MM Pro camera.
The actual focal length is more than 100mm shorter than what I computed it should be with the reducer. What can cause this? Is my spacing correct. I did match it to what was required by making a custom adapter that puts 105 mm between the field flattener and the image sensor.
What are the implications of not having the exact spacing between the field flattener and the image sensor? Is there a way that I can plate solve the image and determine if spacing is needed or a reduction must be made? I want the stars to be focused as best they can on the flattest field of view.