Preliminary Design of ARIES-Devasthal Faint Object Spectrograph and Camera

We present here the preliminary design of ARIES-Devasthal Faint Object Spectrograph and Camera (ADFOSC), which is a multi-mode instrument for both imaging and spectroscopy. ADFOSC is the first-generation instrument to be mounted at the axial port of the Cassegrain focus on our new 3.6m optical telescope to be installed at Devasthal, Nainital. The main design goals of the instrument are : the instrument will have capability of broad- and narrow-band imaging, low-medium resolution spectroscopy, and imaging polarimetry. The operating wavelength range will be from 360 to 1000 nm and the instrument will have remote-control capability.

💡 Research Summary

The paper presents the preliminary design of the ARIES‑Devasthal Faint Object Spectrograph and Camera (ADFOSC), a first‑generation, multi‑mode instrument intended for the axial Cassegrain port of the new 3.6 m optical telescope at Devasthal, Nainital. ADFOSC is conceived as a versatile workhorse capable of broad‑band and narrow‑band imaging, low‑ to medium‑resolution spectroscopy, and imaging polarimetry, covering the full optical window from 360 nm to 1000 nm. The design integrates a slit/ filter wheel, a rotating grating turret, and a polarimetric module within a compact, rigid mechanical envelope that can be remotely operated and automatically focused.

The optical layout begins with a flat tertiary mirror that redirects the converging beam from the telescope to a slit wheel positioned at the focal plane. The slit wheel offers four selectable slit widths (0.5″, 1.0″, 1.5″, 2.0″), allowing the observer to trade throughput against spectral resolution. Downstream, a filter wheel holds ten filters – five broadband (UBVRI) and five narrow‑band (e.g., Hα,