An astronomer's 'Swiss Army Knife'

A brilliant little OSX (Leopard and Snow Leopard) application that allows astronomers to select an observatory, a target object and a calendar date and see how well placed the object is for observing. Shows twilight, UT, local time, Julian Date, moon phase, airmass and lots of other useful data. Great for professional and serious amateur astronomers. Currently late beta, largely bug-free.