"Joe" wrote in message

http://www.analemma.com/Pages/framesPage.html

Probably the best explaination ou there, despite the dodgy sounding URL!

There is also a nice piece of software the

http://www.analemma.com/SunGraph/index.html

that runs on PC and Mac. Hence I can check the sunrise time every
morning, and compare it with reality. Reality is never right.

Trevor
http://www.personal.dundee.ac.uk/~taharley/