lines at 546nm and at 611nm).
address: 'Universität Wien, Institut für Astrophysik, Türkenschanzstra[ß]{}e 17, A-1180 Wien, Austria'
author:
- 'Johannes Puschnig, Thomas Posch, Stefan Uttenthaler'
bibliography:
- 'bibliography.bib'
title: |
    Night sky photometry and spectroscopy\
    performed at the Vienna University Observatory
---

atmospheric effects – site testing – light pollution – techniques: photometric – techniques: spectroscopic

Introduction \[sec:intro\]
==========================

Up to now, astronomers have mainly been measuring the brightness of the night sky (in magnitudes/arcsec$^2$) at dark sites, especially at modern mountain observatories, or at potential observatory sites as a part of “site-testing” and “site-monitoring”. Within the past few years, it has become evident that increasing night sky brightness and light pollution have far-reaching consequences for many branches of human life as well as wildlife (e.g. Posch et al. [@Posch2010]).

Therefore, it is desirable to measure and monitor the night sky brightness not only at remote mountaintop observatory locations (as done, e.g., by Patat [@Patat2008]), but also close to the centers of modern civilization, and to do so every night, in a reproducible way, with the aim of performing long-term studies (such as in climate research). Only in this way can the impact of night sky brightness on biological rhythms 