Algorithm for determining CIE Standard General Sky occurrence from digital sky images

Abstract

The use of digital cameras to capture sky images for measuring sky brightness is an inexpensive and proven method from previous research. However, a digital image has numerous pixels each containing colour data that are impossible to calculate into luminance values manually. Therefore, in this article we describe the algorithm of a computer program that can automate the calculation process and simultaneously compare the measured sky luminance with ISO/CIE Standard Sky luminance, to determine the occurrence frequency.

Keywords:

• ISO/CIE Standard General sky
• Sky luminance