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The Zerbee instrument (1951) is different in one respect:
it solves "two or more" triangles simultaneously,
and this gives you your position directly, not only a line of
position. No need of plotting.

The pictures of these instruments (Zerbee and Hagner) suggest that
they were intended for much higher accuracy than a star globe or an
astrocompass: all scales have verniers. What accuracy could be
actually achieved I don't know. But possibly something like 5 miles,
to match a bubble octant accuracy, I would guess.

Alex.

On Thu, 26 Apr 2012, Geoffrey Kolbe wrote:

>
> List member Wolfgang Koeberer gave a very interesting talk on such
> instruments to the recent National Maritime Museum conference in
> Greenwich (England). The earliest example he showed dated from the
> 16th century, I believe. They were re-invented regularly over the
> succeeding centuries and all had the feature of four intersecting
> circles of adjustment, from which the spherical triangle could be
> solved. The astro-compass was probably the latest (and last)
> instrument to be commercially made in that tradition and Wolfgang
> said that with care, an accuracy of one degree was possible using the
> astro-compass.
>
> Geoffrey
>
> At 13:19 26/04/2012, you wrote:
>
>> For this one we have a patent with good pictures in our list archive:
>> http://fer3.com/arc/img/106506.fix_finder.pdf
>> Unlike the bubble octant, these things are very rare on e-bay,
>> from which I conclude that not so many were produced.
>>
>> Alex.
>>
>> P.S. My son who had a pilot training in 1994, and who works in
>> the airspace industry says that he has never seen a sextant
>> (and it was never mentioned during his training) until I showed him one.
>>
>> On Thu, 26 Apr 2012, G Becker wrote:
>>
>>>
>>> Here is a link to a newspaper blurb on the Zerbee Celestial Fix
>>> Finder... the caption says it was revolutionary in jet navigation. :/
>>>
>>> 
http://news.google.com/newspapers?nid=2206&dat=19511028&id=FJMzAAAAIBAJ&sjid=YOkFAAAAIBAJ&pg=3196,6472009
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>>>
>>> : http://fer3.com/arc/m2.aspx?i=119269
>>>
>>>
>>
>>
>
>
>
>
>
> : http://fer3.com/arc/m2.aspx?i=119271
>
>
>

   

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