Development of the Multi-channel Photometric Survey Telescope

The Multi-channel Photometric Survey Telescope (Mephisto) is a wide-field ground based telescope with a 1.6m primary mirror and 2 degrees field of view, proposed by Yunnan University. The telescope will be capable of imaging the northern sky in three colors simultaneously and deliver a colored movie of the universe. The R-C system with lens corrector was adopted as the optical system considering of the image quality requirement, light obscuration and camera arrangement, in which three cubic splitters were adopted for the three channel beams in order to get satisfied image quality over the whole field of view. Dichroic coating on the cubic will lead to nonuniform efficiency on the focal plane due to the polarization problem and wide incident angle, which need calibration. The image quality represented in 80% encircled light energy is around 0.6arcsec. In order to keep the optimal image quality in any operational conditions, a 5-DOF mechanism was designed to actively adjust M2 mirror positions according to the wavefront sensors or by direct star psf. Now the telescope are under developing in Nanjing, expected to be installed at Lijiang observatory before the end of 2021.