Design of FOSC for 360-cm Devasthal Optical Telescope

A. Omar; R. K. S. Yadav; V. Shukla; S. Mondal; J. Pant

doi:10.1117/12.925841

5 October 2012 Design of FOSC for 360-cm Devasthal Optical Telescope

A. Omar, R. K. S. Yadav, V. Shukla, S. Mondal, J. Pant

Proceedings Volume 8446, Ground-based and Airborne Instrumentation for Astronomy IV; 844614 (2012) https://doi.org/10.1117/12.925841
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

A Faint Object Spectrograph and Camera (FOSC) is designed for the upcoming 360-cm optical telescope at Devasthal. The design is based on other available similar instruments, having a collimator and camera unit. The instrument converts F/9 beam from the telescope to a nearly F/4.3 beam. The collimator and camera optics have 7 and 5 elements respectively with one aspheric component. The low dispersion glasses such as CaF2 and PBM/PBL/FSL are used in order to minimize the chromatic aberrations. These glasses also have very good transmission near blue wavelengths. The imaging is possible both in narrow and broad band filters up to the field of view of ~ 14' x 14' or 19' along the diagonal. The spectroscopy can be performed in the wavelength range 350 - 900 nm with several choices of grisms and slits with resolution in the range of 250 - 2000. The theoretical spot sizes in the imaging mode are expected in the range 0:04" - 0:11". The overall transmission of the camera and collimator optics is expected as ~ 75% at 350 nm and > 95% at wavelengths above 400 nm. The total weight of the instrument as designed is around 350 kg. The instrument is currently planned to be assembled in the Institute laboratory and to be commissioned on the 360-cm telescope in October 2013. The design methodology, techniques, and expected performance of the optics are presented here.

Citation Download Citation

A. Omar, R. K. S. Yadav, V. Shukla, S. Mondal, and J. Pant "Design of FOSC for 360-cm Devasthal Optical Telescope", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 844614 (5 October 2012); https://doi.org/10.1117/12.925841

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