With my equipment my image scale 1.27 and this is what I set up in the defaults. When I do a centering of the image using Plate Solver 2 (via SGP) it solves immediately but then SGP apparently sensing the angle of my camera changes the scale to 1.33. This is just enough to cause the next iteration in the centering process to fail. Is there anyway that I can turnoff SGP’s desire to change my image scale?
SGP doesn’t change your image scale, and the image scale won’t change based
on camera angle. If you are getting a successful plate solve and it says
the scale is 1.33 then that is the true image scale. I suspect you are
using some sort of calculator to determine your theoretical image scale
with your equipment, but in my experience there is always a small
difference between the calculated theoretical scale and the actual scale.
Just put in 1.33 as your default scale and all should be well.
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One other remote possibility. There is an ASCOM command to ask the camera for the pixel size. I bought a Starlight Xpress Superstar and it reported the wrong pixel size. PHD2 then got confused, as it read the pixel size from the camera and got the scaling wrong. It was fixed in 24 hours with a firmware patch for the camera.
Might be worth checking that the camera is reporting the correct size. You can use PHD2 to do that by connecting to it temporarily and read it in the setup screens, or do a short script - querying PixelSizeX and PixelSizeY properties.
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Thanks guys! I will give both of your suggestions a try.