WAHRSIS: A Low-cost, High-resolution Whole Sky Imager With Near-Infrared Capabilities

Cloud imaging using ground-based whole sky imagers is essential for a fine-grained understanding of cloud formations, which can be useful in many applications. Some such imagers are available commercially, but their cost is relatively high, and their flexibility is limited. Therefore, we built a new daytime Whole Sky Imager (WSI) called Wide Angle High-Resolution Sky Imaging System (WAHRSIS ). The strengths of our new design are its simplicity, low manufacturing cost, and high image resolution. Our imager captures the entire hemisphere in a single picture using a digital camera with a fish-eye lens. The camera was modified to capture light across the visible and near-infrared spectral ranges. This paper describes the design of the device as well as the geometric and radiometric calibration of the imaging system.