Sciothericum telescopicum was a

sundial A sundial is a horology, horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the position of the Sun, apparent position of the Sun in the sky. In the narrowest sense of the ...

(sciothericum) that incorporated a telescope (telescopicum) for greater accuracy in determining exactly when noon occurred. It was invented by

William Molyneux William Molyneux Fellow of the Royal Society, FRS (; 17 April 1656 – 11 October 1698) was an Anglo-Irish writer on science, politics and natural philosopher, natural philosophy. He is noted as a close friend of fellow philosopher John Lock ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

in 1686.William Molyneux, “A New Contrivance of Adapting a Telescope to an Horizontal Dial for Observing the moment of Time by Day or Night”, printed by Andrew Cook and Samuel Helsham, 1686
/ref> The device used a telescopic sight to determine the position of the center of the Sun relative to a double

gnomon A gnomon (; ) is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields, typically to measure directions, position, or time. History A painted stick dating from 2300 BC that was ...

and could thus determine the time of noon to within 15 seconds. The improved accuracy was important for geography, navigation and astronomy calculations.Philosophical Transactions of the Royal Society of London, October 1686, No. 184 p. 213 et seq.
/ref>Dn. Johanni Georgio IV, Acta eruditorum, 1687, p 623 et. Seq.
/ref>

References

{{reflist Sundials