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    Re: 7 ways to determine longitude
    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---.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.
    > ================================================================

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