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

William Molyneux William Molyneux FRS (; 17 April 1656 – 11 October 1698) was an Irish writer on science, politics and natural philosophy. He is noted as a close friend of fellow philosopher John Locke, and for proposing Molyneux's Problem, a thought exp ...

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

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 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