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On Thu, 29 Jan 2004 10:30:42 +1100, Kieran Kelly wrote:

>
>One thing which caught my eye and which I invite comment is the passage in
>the Hooke book which says "Accuracy to one second of arc in a hand held
>instrument was not achieved until the early 1920's, when the Swiss
>instrument designer Heinrich Wild produced the  Wild Universal Theodolite"
>(Page 88). Is this true? Was there never a sextant made before this date
>that could measure to the second? Has there been one made since?  I checked
>a couple of modern sextants which measure respectively:
>
>Plath Classic           1/10 minute              6ss
>Plath Professional      1/10 minute              6ss
>Freiberger Yachtsman    1/60 degree              1 minute
>F M Barker Box Sextant 1/60 degree               1 minute
>(Vernier)
>
Possibly the difficulty of making the arc consistent to that fine a
measurement. My 1957 Kelvin & Hughes reads to 10", not quite as fancy
as the Plath. Its certificate gives fixed errors as:

30 deg                 +10"
60 deg                 +10"
90 deg                     0"
120 deg                -30"

If you look at the same info for the Plaths they are probably better,
but not enough better to make a 1" least count meaningful.



Rodney Myrvaagnes   NYC                                                        
                    J36 Gjo/a


"Curse thee, thou quadrant. No longer will I guide my earthly way by thee."  Capt. Ahab

   

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