Observing Conditions and Mid-IR Data Quality

摘要

Ground-based mid-infrared (mid-IR) observations appear to be widely perceived as esoteric and demanding, and very sensitive to observing conditions. Although the principles of observing in the background-limited regime are well-known, it is difficult for the non-specialist to find specific information on exactly how mid-IR data can be affected by environmental conditions. Understanding these effects is important for the efficiency of mid-IR queue observing, the ability of classical observers to adapt their programs to the prevailing conditions, and the standard of data being delivered. Through operating mid-IR instruments in the queue at Gemini we have amassed a considerable database of standard star observations taken under a wide range of atmospheric conditions and in a variety of instrumental configurations. These data can be used to illustrate the effect of factors such as water vapour column, airmass, cloud cover, etc. on observed quantities like raw sky background, residual background, atmospheric transmission and image FWHM. Here we present some preliminary results from this study, which we hope to be of use to observatory users and staff as a guide to which environmental conditions are truly important to mid- IR imaging observations, and which can safely be neglected.