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    Cook and equal altitude sights around noon
    From: Warren Blake
    Date: 2014 Jan 30, 13:04 -0800

    I can add Historical justification for the use of Equal Altitudes of the Sun for determining Apparent Noon. Captain Cook in Endeavour 1768-71 used this method for Apparent Noon, and Lunar Distances to determine the Time at London (now GMT). Comparing these two gave his Longitude to with 30 nm or so, sometimes 10nm. This voyage was without Harisson's Chronometer. In the next two voyages (with this Clock) I am guessing he still used Equal Altitudes but did not need Lunar Distances. As far as I can see at this early stage, he did not use Ex-meridian shots to provide Lines of Position, but am not sure.

    I am presently "Sailing" with him in Endeavour and struggling with Lunar Distances, and the obscure tabulation of data in the Almanac & Ephemeris of 1769. Cook's Astronomers landed where possible to set up Astronomical Quadrants and determined Noon by meridian passage... and of course they observed the Transit of Venus across the Sun, but I have yet to study that. I will swap you selected pages of his Journal with calculations for those Adm. Manual pages you recommend.

    Your outrage at modern sailors who know nothing but a Chart Plotter is justified. Here at my marina in Singapore they venture out into the S. China Sea only if someone enters all the requisite waypoints for them. What they do if they stray off course and get lost beats me!

    Cheers! Captain Blake, Singapore

    [Note from FER: this message has been slightly edited (it was originally addressed as a reply to a message posted in 1997 by a former member who has not been active since 2001)]

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