An Inexpensive Liquid Crystal Spectropolarimeter for the Dominion Astrophysical Observatory Plaskett Telescope

TL;DR

A cost-effective, plug-in spectropolarimeter for the DAO 1.8-m telescope enables high-precision circular spectropolarimetry in the 4700-5300A range, utilizing dual-beam design and fast wave plate switching.

Contribution

Development of an inexpensive, high-precision spectropolarimeter integrated with existing telescope infrastructure for medium-resolution measurements.

Findings

Achieved high-precision measurements with low-cost design

Successfully tested instrument's scientific performance

Optimized for polarization detection in specific wavelength range

Abstract

A new, inexpensive polarimetric unit has been constructed for the Dominion Astrophysical Observatory (DAO) 1.8-m Plaskett telescope. It is implemented as a plug-in module for the telescope's existing Cassegrain spectrograph, and enables medium resolution (R~10,000) circular spectropolarimetry of point sources. A dual-beam design together with fast switching of the wave plate at rates up to 100Hz, and synchronized with charge shuffling on the CCD, is used to significantly reduce instrumental effects and achieve high-precision spectropolarimetric measurements for a very low cost. The instrument is optimized to work in the wavelength range 4700 - 5300A to simultaneously detect polarization signals in the H beta line as well as nearby metallic lines. In this paper we describe the technical details of the instrument, our observing strategy and data reduction techniques, and present tests of its scientific performance.