A Photometricity and Extinction Monitor at the Apache Point Observatory

An unsupervised software ``robot'' that automatically and robustly reducesand analyzes CCD observations of photometric standard stars is described. Therobot measures extinction coefficients and other photometric parameters in realtime and, more carefully, on the next day. It also reduces and analyzes datafrom an all-sky $10 \mu m$ camera to detect clouds; photometric data takenduring cloudy periods are automatically rejected. The robot reports itsfindings back to observers and data analysts via the World-Wide Web. It can beused to assess photometricity, and to build data on site conditions. Therobot's automated and uniform site monitoring represents a minimum standard forany observing site with queue scheduling, a public data archive, or likelyparticipation in any future National Virtual Observatory.Comment: accepted for publication in A