Atmospheric extinction properties above Mauna Kea from the Nearby SuperNova Factory spectro-photometric data set

We present a new atmospheric extinctioncurve for Mauna Kea spanning 3200--9700 \AA. It is the most comprehensive to date, being based on some 4285 standard star spectra obtained on 478 nights spread over a period of 7 years obtained by the Nearby SuperNovaFactory using the SuperNova Integral Field Spectrograph. This mean curve and its dispersion can be used as an aid in calibrating spectroscopic or imaging data from Mauna Kea, and in estimating the calibration uncertainty associated with the use of a mean extinctioncurve. Our method for decomposing the extinctioncurve into physical components, and the ability to determine the chromatic portion of the extinctioneven on cloudy nights, is described and verified over the wide range of conditions sampled by our large dataset. We demonstrate good agreement with atmospheric sciencedata obtain at nearby Mauna Loa Observatory, and with previously published measurements of the extinctionabove Mauna Kea.