Sciothericum telescopicum explained

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 in Ireland in 1686.^[1] 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.^{[2] [3]}

Notes and References

1. https://books.google.com/books?id=YYsPAAAAQAAJ 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
2. https://books.google.com/books?id=3mw1AQAAMAAJ&pg=PA213 Philosophical Transactions of the Royal Society of London, October 1686, No. 184 p. 213 et seq.
3. https://books.google.com/books?id=uBcvbwZtEWQC&pg=PA623 Dn. Johanni Georgio IV, Acta eruditorum, 1687, p 623 et. Seq.