Night-sky brightness and extinction at Mt. Shatdzhatmaz

TL;DR

This study characterizes the night-sky brightness and atmospheric extinction at Mt. Shatdzhatmaz using data from 2007 to 2013, providing median values across multiple photometric bands and analyzing factors affecting measurements.

Contribution

It introduces a technique to correct for biases in sky brightness measurements and transforms MASS data into standard photometric bands for accurate sky quality assessment.

Findings

Median sky brightness: B=22.1, V=21.1, R=20.3, I=19.0 mag/arcsec^2

Median extinction coefficients: B=0.28, V=0.17, R=0.13, I=0.09 mag

Best atmospheric transparency observed in winter

Abstract

The photometric sky quality of Mt. Shatdzhatmaz, the site of Sternberg Astronomical Institute Caucasian Observatory 2.5 m telescope, is characterized here by the statistics of the night-time sky brightness and extinction. The data were obtained as a by-product of atmospheric optical turbulence measurements with the MASS (Multi-Aperture Scintillation Sensor) device conducted in 2007--2013. The factors biasing night-sky brightness measurements are considered and a technique to reduce their impact on the statistics is proposed. The single-band photometric estimations provided by MASS are easy to transform to the standard photometric bands. The median moonless night-sky brightness is 22.1, 21.1, 20.3, and 19.0 mag per square arcsec for the $B$, $V$, $R$, and $I$ spectral bands, respectively. The median extinction coefficients for the same photometric bands are 0.28, 0.17, 0.13, and 0.09 mag. The best atmospheric transparency is observed in winter.