Sciothericum telescopicum

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 site 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]

References
  1. 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. Philosophical Transactions of the Royal Society of London, October 1686, No. 184 p. 213 et seq.
  3. Dn. Johanni Georgio IV, Acta eruditorum, 1687, p 623 et. Seq.
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