The increase in background makes these conditions unusable at thermal infrared wavelengths. The increase in background makes these conditions unusable at thermal infrared wavelengths. See spectra . 1.0mm 1.6mm 3mm any Precipitable H 2 O. See spectra . The atmospheric absorption is strongly wavelength dependent as shown in model transmission spectra .
All values pertain to the zenith.
Optical background values originate from a Monte Carlo simulation of the Mauna Kea sky brightness using a model which includes scattered moonlight and zodiacal light, and pertains to high ecliptic latitude. The sky colour is different between constraint bins. Crudely speaking, the moon is below the horizon during about one half of queue-mode hours. These tabulated values are used to scale an empirical sky spectrum within the integration time calculator. This is the only observing condition constraint required for classically-scheduled observing.