|
Position angle is defined relative to South-North direction, anticlock-wise.
So, PA is:
PA (stars pair) = PA(stars pair, measured on plate) + PA (frame).
If PA (frame is 0, PA = PA (measured)
If for example, PA frame is 5°, and PA (stars pair measured) =15°. that means PA (star par) is 20°.
If result is greater than 360°. then you should subtract 360° to get the proper result.
I agree that the best method to more accurately determine the PA of the frame.would be to take one frame without tracking.
|