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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Index corr. for back sights
From: Alexandre Eremenko
Date: 2004 Nov 20, 15:16 -0500
From: Alexandre Eremenko
Date: 2004 Nov 20, 15:16 -0500
George, "The method hitherto practiced for adjusting that part of the instrument, by means of the opposite horisons at sea, has been attended with so many difficulties that it has scarce ever been used; for so little dependance could be made on the observations taken this way, that the best Hadley sextants made for the purposes of observing the distances of the Moon from the Sun or fixed stars, have been always made without the horizon glass for the back observation; for want of which, many valuable observations of the Sun and Moon have been lost, when their distance exceeded 120 degrees." This is from "A letter from Mr. Peter Dollond, to Nevil Maskelyne, FRS etc. read on March 29 1772 (Trans Royal Soc., you said you have easy access to this). Alex.
