The Tololo all Sky Camera

Abstract

An all sky camera using commercial parts has been assembled at Cerro Tololo Inter-American Observatory to monitor a wide range of atmospheric effects of interest to astronomers, including thin cirrus and contrails which are otherwise invisible on moonless nights, air glow variations, light pollution in the Sodium and Mercury bands, and aircraft lights. To enhance the visibility of clouds, raw images are divided by the corresponding clear sky image, inferred from images taken at the corresponding sidereal time on previous nights. Frames are taken every 30 seconds so that subsequent animation is smooth enough for the eye to pick out motion of clouds at or below the noise floor.