Atmospheric extinction in the near infrared

Abstract

A terrestrial model atmosphere has been used to compute theoretical atmospheric transmissions at very high resolution for various column densities of H2O, CO2, and other molecules. These calculations were used to study the atmospheric extinction for various narrow- and broad-band infrared colors. These computations show that conventional corrections for this extinction by linear extrapolation of stellar observations to zero air mass will yield stellar magnitudes which are too faint, by as much as 0.24 magnitude. This extinction error depends slightly on stellar color. Quantitative results are presented specifically for Kitt Peak and Mauna Kea but should be applicable for the reduction of data obtained at different sites. The extinction problems are found to be especially severe for bandpasses designed to measure stellar water band strengths.