2018 schedule

Sun 1st
11:30-11:45
Mercure Conservatory

The variation of sky brightness with latitude and sidereal time in the absence of Moon or clouds

James Irish

Member, Astronomical Society of Victoria

The "New world atlas of artificial sky brightness" (Falchi et al., 2016) assumes that night sky brightness at dark-sky sites when the Moon is not visible and there are no clouds is 22.0 magnitudes per square arc second for the V spectral band. However, this depends on the solar cycle and, especially for sites in the southern hemisphere, latitude and sidereal time. Results will be presented, together with a model, for sky brightness in eastern Australia. The model is applicable to any site between latitudes 20 and 43 degrees South, and can be generalized to sites affected by light pollution.

James Irish is a retired environmental engineer, whose interests in astronomy therefore extend to pollution. Jim was disappointed when he settled in Melbourne in 2016 by sky brightness, even in the outer suburbs, after living under the heavily-polluted atmosphere of eastern China for a decade. His other astronomical interests are in the physics of the upper atmosphere and its interaction with sky brightness and with astronomical "seeing".