10.4 Sunlight-1 Helioson as a sundial (July 1997)

Sunlight-1 heliodon can be used as a sundial by:

• setting the time scale axis parallel to the axis of the earth, and
• using the 2 parallel north-pointing edges of the adjustable latitude table for setting the solar declination angle [Table 1]

Solar geometric relationships for sundials.

The trim diagram of Artlight-1 heliodon	Artlight-1 heliodon used as a sundial in Hong Kong (22.37°N), set at AST noon on 29 July, 1997	Artlight-1 heliodon/sundial tells the time as 3:15 pm AST on 29 July, 1997

This adjustable latitude table has to be rotated manually about the time scale axis yy (which is now inclined at 22.37 deg w.r.t. to the horizon) which is parallel to the earth axis. The rotation will make the 2 north-pointing edges of the adjustable latitude table to be parallel to sunlight. Read off the time scale for the time - AST.

This sundial tracks the sun, and therefore it is a solar tracking sundial. It can operate in all latitudes in Northern hemisphere and Southern hemisphere, therefore it is a universal sundial.

Provided that the components are manufactured with sufficient accuracy and fine adjustment of the components are possible, by trial and error, this sundial can work without a compass, without first knowing the latitude of the location, even without knowing the day and of course the time.

However a spirit level will be needed to set the baseplate horizontal.

The above illustrations are for working in the Northern Hemisphere. Do you know how to work with it as a sundial in Southern Hemisphere? [Hint: Please look at Sunlight-1 heliodon and the related paper]