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Gordon Talge wrote:

>
> BTW, if you think about it, if the Earth were flat, celestial navigation
> wouldn't work. You would get the same sextant altitude reading for the
> same time of the sun at every latitude, since the sun is so [far]  it's
> rays can be considered parallel.

Not true! That is, if you trust Mary Blewitt's book on "Celestial Navigation for
Yachtsmen". Look at the explanation of the intercept (in the 9th ed., p.18, Fig.
21). Blewitt and with her, T.C. Bergel, the editor of the new edition, apparently
believe in a flat earth.

It is unfortunate that an uncritical use of the 'flagpole paradigm' has crept into
many otherwise good texts on celestial navigation. See, for instance, Susan P.
Howell, Practical Celestial Navigation. As useful as the paradigm might be as a
mnemotechnical aid, it is totally inadequate as an explanation. Personally, I
prefer Computed Greater Away = CGA = Coast Guard Academy. Not only does it work
for negative Hc as well (an upside down flagpole doesn't), but it is so obviously
silly that it could not possibly be mistaken for a real explanation.

Herbert Prinz

P.S.
Gordon Talge actually said 'close', but clearly intended to say 'far'. I took the
liberty to change this in the above quote.

   

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