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    Re: Lunar altitudes
    From: George Huxtable
    Date: 2003 Apr 17, 06:38 +0100

    Fred Hebard said, about the plot of land-based lunar distances, from the
    1850s, that I recently posted-
    > Also, since George had bragged about the
    >data being so good, I assume that his data point at 22h 39m 00s 29d 43'
    >50" was a typo, where the 43' should have been 45', and changed that
    >point accordingly.
    Fred deduced my error correctly. Sorry about the typo.
    On a separate matter altogether, Jan Kalivoda asked a sensible question,
    under this thread on lunar altitudes, a few days ago, as follows-
    >The method of lunar altitudes for finding the GMT seems ideal to me for
    >the observation above an artificial horizon (ashore, of course). The
    >problems with dip, with the blurred sea horizon, with the short period of
    >twighlight would then disappear completely. With an artificial horizon one
    >can wait through the whole night, until the Moon with a star (not very
    >distant from the Moon, but their azimuths don't matter too much in this
    >case) come to the prime vertical. Many occasions can arise through the
    >month and one could expect better results than with lunar distances, isn't
    >it? . This could be very important in early days, when the knowledge of
    >the accurate longitude was an exception outside the Europe and USA (maybe
    >Caribbean) and the method of combining local time and longitude to obtain
    >the GMT was therefore unavailable in remote countries.
    >Had you anybody heard anything about such usage? I didn't.
    >Maybe somebody from the list, who is in possession of a sextant and an
    >artificial horizon, can try this method? It cannot be too difficult, I
    >guess (from the desktop).
    Because I hadn't read Jan's question carefully enough, my response was
    completely irrelevant, referring to lunar-distance measurements rather than
    lunar-altitudes. So once again, sorry about that.
    I agree that the methods proposed by Chichester and others, using lunar
    altitudes rather than lunar distances, would have been more appropriate for
    on-land measurements using a reflecting liquid than they would for sea
    measurements using the horizon. But like Jan, I have seen no account of
    such a method in use on land.
    George Huxtable.
    contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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