skylight v0.9 (beta release)

The skylight package returns sky illuminance parameters for both the sun and the moon, for a given date/time and location. In addition, ancillary parameters such as sun and moon azimuth and altitude are provided. The code is an almost verbatim transcription of the work by Janiczek and DeYoung (1987), published in the US Naval observatory circular. An online copy of this manuscripts can be found on the internet archive (https://archive.org/details/DTIC_ADA182110).