Calibration of the Liverpool Telescope RINGO3 polarimeter

TL;DR

This paper analyzes three years of observational data from the RINGO3 polarimeter to determine and calibrate its instrumental polarisation across three spectral ranges, ensuring accurate polarimetric measurements.

Contribution

It provides a detailed calibration of the RINGO3 polarimeter's instrumental polarisation over multiple years and hardware configurations.

Findings

Instrumental polarisation characterized for blue, green, and red bands.

Calibration data spans over 1126 days and five hardware epochs.

Results enable improved accuracy of RINGO3 polarimetric observations.

Abstract

We present an analysis of polarimetric observations of standard stars performed over the period of more than three years with the RINGO3 polarimeter mounted on the Liverpool Telescope. The main objective was to determine the instrumental polarisation of the RINGO3 polarimeter in three spectral energy ranges: blue (350--640~nm), green (650--760~nm) and red (770--1000~nm). The observations were conducted between 2012 and 2016. The total time span of 1126 days was split into five epochs due to the hardware changes to the observing system. Our results should be applied to calibrate all polarimetric observations performed with the RINGO3 polarimeter.