The Satellite Sundial, Mark 2

[Keeping Up]

When I first devised the Satellite Sundial as an easy way to find the Sky TV satellite, I knew that it was just an approximation which was relatively inaccurate. Since then several people have asked me when a more accurate version would be available. Well, at long last HERE IT IS.

 

This winter I set myself the project of understanding enough of the complex maths involved, to produce a better sundial. The problem is that when viewed from the Earth, the Sun moves in mysterious ways. Fortunately I dicovered an excellent article on Analemmatic sundials, from which I ws able to understand the principles well enough to work the equations backwards and find true South when knowing the time and date. Working from the sun's angle of declination and adding corrections for latitude, longitude, and the gloriously named "equation of time", the results surprised me; if my mathematics are correct, the old sundial could be as much as an hour and three-quarters out.

 

The bad news is that to get the required accuracy you need to use a different sundial each month, so there are twelve sheets of paper to be printed. The good news is that the results should be accurate to within a few degrees at all times. I have based the dials on Birmingham (which I have arbitrarily taken to be roughly the centre of the canal network), and the error across the whole canal system should never exceed 2 degrees mid-month. It may reach 5 degrees at the beginning or end of the month but that should still be near enough to let you find the satellite fairly quickly.

 

Just click here for a link to the series of 12 printable sundials (and brief instructions on how to use them)

 

I have shown here the January sundial as an example. Any feedback would be much welcomed.

 

[twocvbloke]

Very good, only useful for Astra 2, but I'm sure it could be adapted for other satellites (for those in the hobby of channel hopping!!!)...