Atmospheric Extinction Coefficients and Night Sky Brightness At the Xuyi Observational Station

TL;DR

This study measures atmospheric extinction and night sky brightness at Xuyi Observatory, revealing relatively high extinction likely due to low elevation and humidity, based on extensive CCD imaging data from 2009-2011.

Contribution

It provides the first comprehensive measurements of atmospheric extinction and sky brightness at Xuyi Observatory using multi-year CCD data.

Findings

Extinction coefficients are 0.70, 0.55, 0.38 mag/airmass for g, r, i bands.

Median sky brightness values are 21.7, 20.8, 20.0 mag/arcsec2.

Sky brightness reaches 22.1, 21.2, 20.4 mag/arcsec2 under optimal conditions.

Abstract

We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observational Station of Purple Mountain Observatory (PMO). The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey g, r and i bands with the Xuyi 1.04/1.20m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC), the photometric part of the Digital Sky Survey of the Galactic Anti-center (DSS-GAC). The data were collected in more than 130 winter nights from 2009 to 2011. We find that the atmospheric extinction coefficients for the g, r and i bands are 0.70, 0.55 and 0.38 mag/airmass, respectively, based on observations taken in several photometric nights. The night sky brightness determined from images of good quality has median val- ues of 21.7, 20.8 and 20.0 mag/arcsec2 and reaches 22.1, 21.2 and 20.4 mag/arcsec2 under the best observing conditions for the g, r and i bands, respectively. The relatively large extinction coefficients compared with other good astronomical observing sites are mainly due to the relatively low elevation (i.e. 180 m) and high humidity of the Station.