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Subject: Re: Lunar altitudes
From: George Huxtable (george@XXX.XXX)
Date: Thu Apr 17 2003 - 01:38:44 EDT
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.
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contact George Huxtable by email at george@XXX.XXX 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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