 Check out the bookstore at IRBS.com |
|
|
|
|||||
|
||||||
Subject: visibility at rising and setting
From: George Huxtable (george@XXX.XXX)
Date: Wed Apr 26 2000 - 16:32:24 EDT
Thanks to all on the list who contributed a bagful of useful responses to
my question about whether stars and planets were ever visible at the moment
of rising or setting.. Particularly to Thomas Schmidt
<schmidt@XXX.XXX Brad Schaefer of
Yale, schaefer@XXX.XXX I have had a prompt response from
Prof Schaefer, and an authoritative one.
Schaefer states firmly that stars are never visible down to the horizon,
but under very exceptional conditions there is a chance that Venus at its
brightest might be seen as it rises and sets; with normal skies, not a
hope. There seems to be some support for this view in the collective
experience of list members. It also confirms my own prejudices; therefore I
believe it implicitly.
----------
I can fill in some of the gaps in the story of the yachtsman who sailed
round the world without instruments. He was Marvin Creamer, a geography
professor from Glassboro State College, New Jersey. He took his departure
from Cape May in 1982, with crew, in Globe Star, a 36-foot steel cutter. He
returned in 84, having put in at Cape Town, Hobart (Tasmania), and Stanley
(Falklands). He did not use a single instrument, though they were sealed up
in a bag just in case. He eschewed even compass, log, and wristwatch,
though he did carry an hourglass, for changes of watch! He had made
previous uninstrumented passages, from Ireland to New Jersey, and a round
trip from New Jersey to Dakar (West Africa), returning via the island
landfalls of Cape Verdes and Bermuda. My information comes from the issue
of "Navigator" dated July/August 1985, pages 30-35. He also read a paper at
the Institute of Navigation annual meeting, Annapolis 6/85, entitled "The
first circumnavigation without instruments: a small step backward", of
which I have a photocopy.
Creamer obtained his latitudes by identifying a star with known declination
that happened to transit through his zenith, directly overhead, estimating
this by simply looking straight upward, after a lot of practice. He was
just as unaware of his longitude as was an eighteenth-century mariner, so
had to sail down a parallel of latitude to reach his landfall. It's the
sailing without a compass that I find most awesome.
----------
George
------------------------------
george@XXX.XXX
George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
Tel, or fax, to 01865 820222 or (int.) +44 1865 820222.
------------------------------
|