An analysis of the fragmentation of observing time at the Muztagh-ata site

Abstract

Abstract Cloud cover plays a pivotal role in assessing observational conditions for astronomical site-testing. Except for the fraction of observing time, its fragmentation also wields a significant influence on the quality of nighttime sky clarity. In this article, we introduce the function Γ ∈ [0, 1], designed to comprehensively capture both the fraction of available observing
time and its continuity. Leveraging in situ measurement data gathered at the Muztagh-ata site
between 2017 and 2021, we showcase the effectiveness of our approach. The statistical result
illustrates that the Muztagh-ata site affords approximately 122 nights of absolute clear and
205 very good nights annually, corresponding to Γ ≥ 0.9 and Γ ≥ 0.36 respectively.