NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Visibility at rising and setting
From: George Huxtable
Date: 2000 Apr 26, 2:32 PM
From: George Huxtable
Date: 2000 Apr 26, 2:32 PM
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, who referred me on to Prof. Brad Schaefer of Yale, schaefer@grb2.physics.yale.edu. 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@huxtable.u-net.com George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. Tel, or fax, to 01865 820222 or (int.) +44 1865 820222. ------------------------------