The site conditions of the Guo Shou Jing Telescope

TL;DR

This study analyzes the site conditions at Xinglong Observing Station, assessing how weather, sky brightness, and seeing affect the LAMOST survey schedule and capabilities from 1995 to 2011.

Contribution

It provides a comprehensive statistical analysis of site conditions and their impact on the LAMOST survey planning and observational constraints.

Findings

Operable hours vary seasonally, with up to 8 hours in December and 1-2 hours in July-August.

Seeing worsens in windy winters; atmospheric extinction peaks in spring and summer.

The site allows a magnitude limit of V=19.5 with S/N=10 for the survey.

Abstract

The weather at Xinglong Observing Station, where the Guo Shou Jing Telescope (GSJT) is located, is strongly affected by the monsoon climate in north-east China. The LAMOST survey strategy is constrained by these weather patterns. In this paper, we present a statistics on observing hours from 2004 to 2007, and the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site. We investigate effects of the site conditions on the survey plan. Operable hours each month shows strong correlation with season: on average there are 8 operable hours per night available in December, but only 1-2 hours in July and August. The seeing and the sky transparency also vary with seasons. Although the seeing is worse in windy winters, and the atmospheric extinction is worse in the spring and summer, the site is adequate for the proposed scientific program of LAMOST survey. With a Monte Carlo simulation using historical data on the site condition, we find that the available observation hours constrain the survey footprint from 22h to 16h in right ascension; the sky brightness allows LAMOST to obtain the limit magnitude of V = 19.5mag with S/N = 10.