Polarimeter for the HELLRIDE instrument at Vacuum Tower Telescope

摘要

Vacuum Tower Telescope is a 70 cm off-axis solar telescope situated at Teide Observatory, Tenerife. It hosts a suit of instruments including HELioseismic Large Region Intcrferomctric DEvice (HELLRIDE). HELLRIDE is a dual Fabry-Perot etalon-based imaging spectroscopic instrument. It records solar activity at, multiple heights by means of multi-line spectroscopy with a cadence of less than a minute. Polarimeter development for the aforementioned instrument is discussed, towards producing the magnctograms at high cadence. Liquid crystal variable retarders and Polarizing beam-splitter are chosen as polarimetric modulators and analyzer respectively. A broadband imager is designed to acquire continuum images at the same time as polarized images. Two spectral lines arc selected for the polarimetric observations: Fe_Ⅰ6302.5 A and Ca_Ⅱ 8542 A, with a scope for adding more lines.