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    Lunars for exploration: western China in 1870
    From: Frank Reed
    Date: 2012 Oct 6, 12:05 -0700

    Lunar observations for longitude, which were mostly finished in maritime practice (with rare exceptions) by 1850, were frequently used by land-based explorers for a few more decades since chronometers do not fare well when transported by pack animals.

    Here's an example from September 1870:
    "...the vexed problem of the longitude of Yarkand (placed by the Schlagintweits [Bavarians who had explored in the Himalayas and Central Asia in 1854] about 200 miles too far to the west) had been solved by the recent lunar observations of Mr. Shaw, the computation of which had been completed that day, at the request of the Geographical Society, by Mr. W. Ellis, of the Greenwich Observatory. These observations placed Yarkand in E. long. 77° 14' 45"."

    Checking Google Maps, that appears to be quite accurate. Yarkand is in the far west of China today, and that longitude is very close to the center of town, within a fraction of a mile. This brief quotation is from an issue of the "Nautical Magazine". There are quite a few editions available through Google Books, and they're filled with all sorts of fascinating information, much of it firsthand accounts.

    The observations by Shaw at Yarkand were published in more detail in the Proceedings of the Royal Geographical Society. I am attaching a page image with the details in case anyone wants to work up these lunars with modern tools. Does the accuracy hold, or was it a lucky accident??


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