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    Re: Lat/Long by Noon Sun
    From: Gary LaPook
    Date: 2009 Apr 27, 15:15 -0700

    Well I was impressed by the level of accuracy they achieved since it
    is much better than the 5 nm level of accuracy that has been discussed
    lately using sun sights around the time of noon.
    
    gl
    
    On Apr 27, 10:49�am, "George Huxtable"  wrote:
    > Gary Lapook wrote, in response to a posting by Henry Halboth-
    >
    > You might be surprised by the level of accuracy in determining the longitude
    > from equal altitude 
    sights:http://articles.adsabs.harvard.edu//full/1919PA.....27..359W/0000359....http://articles.adsabs.harvard.edu//full/1919PA....27..359W/0000363....
    >
    > (most of the "meat" is in the first of these links)
    > =====================
    >
    > Comment from George-
    >
    > This was an interesting 1916 paper which, in part, describes the preliminary
    > determination by sextant of the location of an observation station near
    > Baker, Oregon, which later became accurately known by precise astronomy.
    >
    > It was made using equal altitudes of the Sun, presumably (though we are not
    > given such details) using an artificial horizon.
    >
    > I don't think anyone should be surprised by the accuracy achieved. Indeed,
    > it was worse than they expected, being out by about 1 second of time (15
    > arc-seconds) in longitude, and nearly half a minute in latitude. This,
    > despite many averagings over several days, with none of the uncertainties
    > that arise when looking at a real horizon from the deck of a vessel.
    >
    > Although it's been posted under the threadname "Lat/Long by Noon Sun", it
    > really had nothing to do with a noon Sun. The author tells us that his equal
    > altitudes were taken in the forenoon and the afternoon, without stating
    > exactly what time. But I suspect that they were made several hours apart, so
    > that the two Sun azimuths differed by somewhere near to the optimum angle of
    > 90 degrees.
    >
    > They ended up suspecting that errors in the latitude could be due to
    > inaccuracies in their Brandis sextant, though that shouldn't affect the
    > equal-altitude longitudes.
    >
    > I'm unsure about the lessons that Gary expected us to draw from that paper
    > (he didn't say) but it tells us nothing about longitude-around-noon (except
    > that it's avoided when precision is called for), and had no relevance to the
    > points Henry was making.
    >
    > George.
    >
    > contact George Huxtable, at �geo...{at}hux.me.uk
    > or at+44 1865 820222(from UK, 01865 820222)
    > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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