图 1：Mephisto望远镜效果图；Mephisto Telescope

1.6米多通道测光巡天望远镜由中国科学院国家天文台南京天文技术光学研究所负责研制，其基本参数参见表1，效果图见图1。望远镜主镜口径1.6m，系统焦比4.5，创新性地采用 Ritchey-Chretien系统加改正镜结合镀膜分光立方棱镜的光学系统（图2），可同时满足大视场（视场直径2°），宽波段（0.32-1 μm），像质好（80%EE < 0.6′′），挡光小，后端光路分光实现多通道等要求，能同时在3个波段拍摄天空数字图像，获取天体超高精度实时颜色信息，巡天速度高达每晚3个波段1200平方度，与LSST相比拟。

The Nanjing Institute of Astronomical Optics & Technology (NIAOT) is responsible for the Mephisto telescope construction. Mephisto (Fig.1) is designed to have a 1.6m primary mirror with a focal ratio of 4.5. To simultaneously meet the requirements from large field of view (2° FOV)，wide bandpass (0.32-1 μm), high imaging quality (80%EE < 0.6′′), small light obscuration and multi-channel light splitting in the back-end optical path, an innovative optical system (Fig.2) including Ritchey-Chretien system with correctors and films coated cubic prisms for beam-splitting is adopted. Mephisto will simultaneously imaging the same patch of sky in three bands (ugi or vrz), yielding real-time colours of astronomical objects with unprecedented accuracies, and delivering for the first time a coloured documentary of our evolving universe. The survey speed could be as fast as 1200 deg2 in 3 bands per night, almost comparable to LSST.

图 2：Mephisto光路图；Mephisto light path

表 1：望远镜主要参数；key parameters of Mephisto

望远镜采用传统赤道式机架结构，总重约28吨。为保障像质，望远镜配备五维调节机构，会根据焦平面上装配的波前传感器主动调整副镜位置。

Mephisto adopts the classical equatorial mount which is very compact and stiff.  The weight of the complete telescope is approximately 28 tons. In order to keep the image quality always optimal in any operational condition, a 5-dimensional regulating device is equipped to actively adjust secondary mirror position according to the wavefront sensors assembled in the focal plane.

望远镜控制系统（TCS）负责瞄准、跟踪、副镜控制、滤光片切换、导星等功能。控制系统采用直驱电机，能有效提高机械谐振频率并扩展带宽。主控制器采用Power PMAC，扩展模块采用PWM控制器和4096细分高精度采集卡。

Telescope Control System (TCS) is responsible for pointing, tracking, secondary mirror control, filter switch, guiding and so on. Direct drive motor is used to improve the mechanical resonance frequency and expand the bandwidth of the control system.The master controller of the TCS adopts Power PMAC, and the extension modules adopt PWM controller and 4096 subdivision high-precision acquisition card.

望远镜于2018年10月开始研制，整体进展顺利，目前已完成主镜加工，机电进入全面装配阶段，预计2021年完成在站安装调试、实现初光。望远镜建成后，将对快速探测、分类宇宙变源、暂现源，发现新现象、揭示新物理发挥重要作用。

The development of the telescope started in October 2018, and good progress was made. At present, the processing of the primary mirror is completed and the secondary mirror is in the final stage of polishing and testing, and the electromechanical system has entered the stage of comprehensive assembly. It is expected to complete the on-site telescope installation and commission and realize the first light by the end of 2021. It is expected that the unique capability of recording high-precision real-time colours will allow quick and robust classification of fast transients, makes Mephisto particularly powerful for time domain astrophysics.