Telling the Time by the Stars

Recently, I mentioned that Stokey had shared with the Allnatt Centre's staff his method of telling the time from the stars, which we had later put into practice on a clear, starry night.
If you want to have a go, here it is:
First, locate the constellation known as the Plough, Ursa Major or Big Dipper:

The stars marked α and ß are Marak and Dubhe and can be used as a pointer to the brightest star in the sky, Polaris. Next, imagine a clock centred on Polaris, but upside down and back to front. Take the number the pointer shows (the Sky Hour) and double it (1 x 2 =2). Then take the month and double that (e.g. August is the 8th month so 16). Add the two together (18) and take that away from 41.5 = 23.5. So the time in this example would be 11.30pm!

Easy! Try it out next time there's a clear sky!