Paper

Bright-Moon Sky as a Wide-Field Linear Polarimetric Flat Source for Calibration

Pavlidou, V, Potter, S B, Skalidis, R, Blinov, D, Mandarakas, N, Ntormousi, E, Pearson, T, Pelgrims, V, Readhead, A C S, Anche, R M, Papadaki, A, Basyrov, A, Wehus, I K, Panopoulou, G V, Kiehlmann, S, Tassis, K, Gjerløw, E, Deka, K, Eriksen, H K, Maharana, S, Ghosh, T, Ramaprakash, A N, Kypriotakis, J A

2023

Overview

Next-generation wide-field optical polarimeters like the Wide-Area Linear Optical Polarimeters (WALOPs) have a field of view (FoV) of tens of arcminutes. For efficient and accurate calibration of these instruments, wide-field polarimetric flat sources will be essential. Currently, no established wide-field polarimetric standard or flat sources exist. This paper tests the feasibility of using the polarized sky patches of the size of around ten-by-ten arcminutes, at a distance of up to 20 degrees from the Moon, on bright-Moon nights as a wide-field linear polarimetric flat source. We observed 19 patches of the sky adjacent to the bright-Moon with the RoboPol instrument in the SDSS-r broadband filter. These were observed on five nights within two days of the full-Moon across two RoboPol observing seasons. We find that for 18 of the 19 patches, the uniformity in the measured normalized Stokes parameters \\(q\\) and \\(u\\) is within 0.2 %, with 12 patches exhibiting uniformity within 0.07 % or better for both \\(q\\) and \\(u\\) simultaneously, making them reliable and stable wide-field linear polarization flats. We demonstrate that the sky on bright-Moon nights is an excellent wide-field linear polarization flat source. Various combinations of the normalized Stokes parameters \\(q\\) and \\(u\\) can be obtained by choosing suitable locations of the sky patch with respect to the Moon

• Publisher: Cornell University Library, arXiv.org
• Subject: Broadband / Calibration / Linear polarization / Moon / Patches (structures) / Polarimeters / Polarimetry / Stokes parameters