Flexure Measurement - How Much is Too Much ?

M Hambrick

Roland has stated on multiple occasions that using a separate guide scope is not the ideal way to do guided imaging because of flexure. How much flexure is considered excessive ? I believe that it was also Roland who suggested a way to detect flexure by using the information box in MaxIm DL to measure the position of the guide star in the main imaging camera at the start and at the end of the guiding session. The assumption is that the guide star position in the guiding camera will not change, but if there is flexure, it can be seen as a shift in the position of the star in the main imaging camera.

I tried this the other night. It was a very short session because the seeing was so bad, but after a single 600 second exposure I measured the shift in the position of the guide star centroid to be 0.053 pixels in the X-direction, and 0.304 pixels in the Y-direction. This doesn't seem to be too bad in the X-direction, but I am not so sure about the Y-direction. Does anyone have any thoughts on this ?


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