Theoretical Calculation of the Field-of-view Rotation Angles for the 1.2m Altazimuth Telescope in the Yunnan Observatory

In this paper, we analyze the rotation of an image from the 1.2m astronomical telescope due to the azimuthal and altitudinal rotations of its coude mirror system.The rotation of field-of-view is analyzed using the ray tracing and matrix optics.The two methods yield a consistent function describing the variation of object-image rotation with the telescope azimuth and zenith.The object-field rotation in the spherical coordinates as caused by the altazimuth mounting is transformed into that in the Cartesian coordinates on the CCD plane.The field-of-view rotation of the 1.2m telescope system is finally derived, providing the theoretical basis to correct such a rotation in real time.