How to use your Sundial Glass.

Map showing places within a degree or so of 51 degrees longitude in the UKOur Sundial Glass does not have to be fixed in one position as most dials are.  This type of dial is known as an altitude dial and it is turned throughout the day so the sun always shines through the ring onto the current month.  No compass is needed to use it.  It is designed to be used at 51° north, although it will read pretty near the correct time within a few degrees of this – in other words, right across southern England, south and central Wales and into the Midlands.

Sundial Glass in the sun showing timeFirst, either start with an empty glass or drink some of your beer: not too much, just so the current month is above the beer.  This is because light is refracted differently through liquid.  Then place the glass on a level surface and turn it until the sun shines through the ring and onto the month you are in.  Select the part of the column that relates to the date – if it is the 15th, aim the beam of sunlight at the middle.   The time can then be read off on the hour lines that go across the glass.

Glass showing circle to shine sun throughYou will find that, as time progresses and the sun moves through the sky, you will have to turn the glass round so the sun still shines on the same date.  The beam of sunlight will move upwards if you are in the afternoon or down towards noon if you have started drinking in the morning.

Solar time does not take account of summer time, longitude, or that days are of different lengths throughout the year.  It’s just 100% sun time, no added extras.

If you want to relate it to a clock, this is possible and easy.