High-Resolution Diffraction Grating Filter Holder Design

Spectroscopic capabilities are typically reserved for large telescopes operated by large colleges and universities and are not seen with smaller colleges and universities. Our current miniature grism (Patent No.US20170357038A1) is a 3D printed housing that contains 5 optical elements and is installed in the filter wheel. This grism includes a 600 line/mm with a peak spectral resolution of 1.1nm VPH (Volume Phase Holographic) grating. We present a new grism design with a compound grating-prism element with a 2000 lines/mm VPH tuned for a maximum efficiency of 70% at 656nm with a max spectral resolution of <0.3nm (<150km/s at H-). The changes made to this design entail modifying the current grism housing to be compatible with this new grism, creating and testing this housing on an optical table to demonstrate the expected performance increase. We expect that at max resolution, we will be able to make precise measurements of H- doppler broadening from Be stars caused by a decretion disk from near-critical rotation. The miniature grism was originally installed on the Robert L. Mutel Telescope (RLMT) at Winer Observatory in Sonoita, AZ, and is currently operated by the Macalester, Augustana, Coe College, Remote Observatory (MACRO) Consortium.