All Sky Imager (ASI)
Mentor: J.H. Schween
We use an commercially available fish-eye surveillance camera to collect images of the sky and determine cloud amount. The camera is an AXIS M3027-PVE Fixed Dome Network Camera with a common Omnivision CMOS rgb-sensor. Images with a resolution of 800×600 pixels (BMP format) are taken every 20sec. Every pixel above the horizon is investigated for its blue-to-red-ratio and categorized as sky (blue), thin-cloud (light-blue) or cloud (white or gray). Pixels are counted and stored as relative cloud amount as well as palette based png images. From the number of satured pixels around the sun a flag for the visibility of the sun is derived.
The camera replaced a YES total sky imager which died after some years of operation.