Shafting System Upgrade for the Solar Magnetism and Activity Telescope

In astronomical observation, telescopes need to be able to quickly and accurately point to the object body (such as the solar) and track them stably. In this paper, the shaft system upgrade is performed for The Solar Magnetism and Activity Telescope (SMAT) in Huairou Solar Observing Station (HSOS). We use 23-bit high-precision absolute encoder on the servo motor to replace the angle encoders with graduation on steel tape. Real-time calculation of the center position of the solar is performed through VSOP87 planetary theory, and a high-precision guiding system base on a large area CCD is used to continuously track the solar and record the position of the sun. The least square method is used to segmented fit the real time position of the sun and the value of the absolute encoder. Finally, the pointing algorithm is established and the solar center pointing is realized. According to the actual measurement, the pointing error of right ascension direction is about 36.69″, and that of declination direction is about 21.49″. The proposed method meets the requirements of SMAT, has low cost and high compatibility, and is of referential significance to the upgrading of other equatorial telescopes.