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Peter Fogg wrote:
> All agree that there is a false horizon line, where the moon's
> relected light is cut off, some way between the real horizon and the
> point of observation.
Provided that the Moon's altitude is high enough. For any given sea
state and height of eye, there must be some altitude below which rays of
light from the Moon strike the observer's horizon and there reflect to
his eye.
Presumably, it is when the Moon is below that altitude that the
irradiation effect becomes important and the false horizon rises above
the real horizon. At a guess, small boats and high latitudes tend to
make for reflected light reaching to the true horizon and hence a raised
false horizon while large heights of eye and low latitudes tend to give
the reverse -- though I have never attempted a sextant sight under
either set of conditions, so this is purely theoretical for my part.
Trevor
--
Trevor J. Kenchington PhD
Gadus Associates, Office(902) 889-9250
R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251
Nova Scotia B0J 2L0, CANADA Home (902) 889-3555
Science Serving the Fisheries
http://home.istar.ca/~gadus
