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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...@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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