Design and development of Cassegrain module for PARAS-2 spectrograph (CAMPAS)

We present here the design and development of the Cassegrain Module for the PARAS-2 spectrograph (CAMPAS). PARAS-2 is a high-resolution fiber-fed echelle spectrograph developed for the PRL 2.5 m telescope. The CAMPAS acts as a coupler between two optical systems, the PRL 2.5 m telescope and the PARAS-2 spectrograph. It has primarily been developed for the precise injection of the light beam into the optical fibers of the PARAS-2 spectrograph. The CAMPAS consists of a focal reducer, beam-guiding optics, an atmospheric dispersion corrector, optical fiber mounts, a calibration unit incorporating calibration lamps and beam-guiding optics, and other auxiliary subsystems. It was developed in-house at PRL, Ahmedabad, between the years 2020 and 2022 and was installed at one of the two side ports of the PRL 2.5 m telescope in March 2022. It is one of the first light instruments for the PRL 2.5 m telescope. The CAMPAS serves critical purposes of precise fiber feed, point spread function estimation, and atmospheric dispersion correction.