Designs of Mt. Abu faint object spectrograph and camera-echelle polarimeter (M-FOSC-EP) and its prototype: spectro-polarimeters for PRL 1.2m and 2.5m Mt. Abu telescopes, India

Mt. Abu Faint Object Spectrograph and Camera-Echelle Polarimeter (M-FOSC-EP) is a two-channel multimode instrument currently under design for the upcoming PRL 2.5m telescope at Mt. Abu, India. M-FOSC-EP would provide capabilities of seeing limited imaging, low-resolution spectroscopy (R∼500-800), and high-resolution spectro-polarimetry (R∼15000) over the visible waveband. This design uses a common collimator optics, followed by a movable fold mirror to direct the incoming telescope beam into either of the low-resolution and spectro-polarimetry modules, which are equipped with their separate detector system. As a precursor of M-FOSC-EP, a prototype spectro-polarimeter named ProtoPol is also being developed with commercially off-the-shelf optical components. ProtoPol could be used on existing 1.2m as well as on upcoming 2.5m PRL telescopes. Here we present the optical designs and performances of M-FOSC-EP and ProtoPol. In addition, the opto-mechanical design of ProtoPol has been presented.