I felt compelled to plot Brian's data. http://members.cox.net/tpolakis/astro/SQMsunset1.jpg http://members.cox.net/tpolakis/astro/SQMsunset2.jpg In the latter plot, I have run the desktop planetarium software to compute the solar depression angles. Tom -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.