NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: 7 ways to determine longitude
From: Fred Hebard
Date: 2003 Dec 24, 13:48 -0500
From: Fred Hebard
Date: 2003 Dec 24, 13:48 -0500
The title of this book may be "Manual of Spherical and Practical Astronomy". Some of the older editions have an additional subtitle. There is a 1960 edition. On Dec 24, 2003, at 12:31 PM, George Huxtable wrote: > Dan Allen said- > >> I have just started to read an old book called "Spherical and Nautical >> Astronomy", a two volume set by William Chauvenet who was a professor >> at Washington University in St. Louis. My copy was printed in 1903 >> but >> it appears that it is just a reprint of an 1863 edition. >> >> Chapter 7 is "Finding Longitude by Astronomical Observation" where it >> lists seven different methods, which are: >> >> "1st method - by portable chronometers >> 2nd method - by signals >> 3rd method - by the electric telegraph >> 4th method - by moon culminations >> 5th method - by azimuths of the moon, or transits of the moon >> and a star over the same vertical circle >> 6th method - by altitudes of the moon >> 7th method - by lunar distances" >> >> By chronometers it means chronometric expeditions: taking a >> chronometer >> from Greenwich to Boston and comparing mean noon times. By signals it >> includes eclipses, occultations of Jupiter's moons, and terrestrial >> signals. > > =============== > > Chauvenet (presumably, from his name, of French extraction) was one of > the > important names in early American science. (In astronomy, Simon > Newcomb was > the next, to establish the American lead over the rest of the world in > astronomical matters). Chauvenet's great two-volume work was intended > for > astronomers and surveyors, rather than for the more simple-minded > navigator, I suspect. It is remarkably thorough and comprehensive. > Lots of > detailed drawings of survey instruments and telescope mounts. > > It's the only published work that I have seen, which assesses the > (small) > effect of the elliptical shape of the Earth on the AZIMUTH of the Moon. > That doesn't affect any observations involving just the Moon's > altitude, > but it does, of course, affect the oblique lunar distance to another > body; > an effect that's usually neglected. > > I have never seen any note, in a subsequent work, drawing attention to > an > error in Chauvenet, so I conclude he got it all right. > > The chronometer expeditions that Dan mentions were big business before > the > telegraph came in. Literally dozens of chronometers were shipped > bachwards > and forwards between Greenwich and Dublin, time and again, to establish > their longitude difference. Also between German observatories and > Pulkovo > (St Petersburg). Does anyone know whether chronometers were ever > shipped up > the Mississippi for that purpose, before the days of the telegraph? Or > sent > by pony express, even, if they could withstand the rigours of that > journey? > > My own copy of Chauvenet has a text-date on the preface of 1863, like > Dan's, but otherwise says nothing about its date other than "5th > edition". > Does Dan have an edition-number with his 1903 printing, that might > help to > fix the date of my own copy better? > > George. > > ================================================================ > contact George Huxtable by email at george@huxtable.u-net.com, by > phone at > 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy > Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. > ================================================================ >