Enthusiasms

This Month: Sundials

- LUKE HONEY

A few years ago, we bought my father a sundial. It was a decent 18th-century style reproduction in lead - something he had wanted for a very long time - and then, inevitably, he asked me to help him set it up. After an initial search, I soon realised a bit of insider know-how was necessary. And, as it turns out, in order to guarantee an accurate reading, you must install it at a specific time, and to face a specific direction.

For those in the Northern Hemisphere, the genome (the shadow-casting pointer) must be facing True North, parallel with the Earth's axis. Needless to say, you'll want a compass to confirm this. According to Queens' College, Cambridge, which boasts a 17th-century painted sundial on the wall of its quad, if you're in the United Kingdom, you should set it in the correct position at noon on either 16th April, 15th June, 1st September or 25th December. These are the four dates when your sundial is closest to the local meantime: the moment Solar time aligns with Earth time. Please don't ask me why exactly; I'm not the world's greatest mathematician, but I do trust many hundreds of years of astronomical calculations.