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    Re: PVH Weems. Was Sidereal Hour Angle vs. Right Ascension
    From: Fred Hebard
    Date: 2005 Aug 17, 08:50 -0400

    If you can get a copy of the Navy's booklet on space navigation (as in
    rocketships to the moon, etc), it is fascinating to read for how it was
    put together, as well as for the proposed techniques.  It was developed
    by Weems in the late 50s, early 60s, with the help of smart, freshly
    minted officers from naval reserve officer training programs at various
    civilian universities around the country.
    On Aug 17, 2005, at 8:27 AM, Robert Eno wrote:
    > Thanks Bruce,
    > Your mention of PVH Weems is interesting. I believe that this man's
    > name is not as well known as it should be for he seems to figure
    > prominently in many old navigation texts as an inventor, innovater and
    > generally a brilliant navigator.
    > I have, in my collection, a number of delightful, slim, red volumes
    > from the "Weems System of Navigation", including one called: "A Short
    > History of Navigation".
    > It is not only Weems, but our American friends in general, who made
    > significant contributions to the art and science of celestial
    > navigation, starting from Nathaniel Bowditch (it could be argued that
    > he was more a Brit, but he was born and bred in the fledgling United
    > States) and culminating in the 1930's, 40's and 50's, with men such as
    > Weems.
    > My views on the contemporary history of navigation could be skewed,
    > given that my navigation training and mentorship was influenced
    > largely by Americans, however, I do not believe that the United States
    > gets the credit that they are due, for their contributions. PVH Weems
    > is one such example.
    > Robert
    >> ----- Original Message -----
    >> From: Bruce Stark
    >> Sent: Tuesday, August 16, 2005 2:24  PM
    >> Subject: Re: Sidereal Hour Angle vs. Right Ascension
    >> Robert,
    >> I'm pretty sure sidereal hour angle wasn't used in the American
    >> Nautical Almanac before 1950. But, for all I know,  it was in the Air
    >> Almanac from the beginning of that publication.
    >> You're not alone in preferring SHA to right ascension. SHA fits the
    >> Greenwich hour angle approach to celestial navigation, which is the
    >> only approach anyone understands now. As you know, SHA is RA turned
    >> backward, to  increase from east to west, and given in arc, rather
    >> than time. It would have been as awkward for the nineteenth-century
    >> navigators as RA is for us.
    >> Since sidereal hour angle was designed to work with Greenwich hour
    >> angles, the idea of GHA had to come first. I believe the GHA approach
    >> to  celestial navigation was developed by P. V. H. Weems, as a way to
    >> simplify air navigation. It first got a toehold in the American
    >> Nautical Almanac in 1934. Here's a quote from the 1934 Preface.
    >> Notice the mention of air navigation.
    >> "The object of this volume is to provide the navigator, including the
    >> aerial navigator, with a compact publication containing all of the
    >> ephemeris material essential to the solution of problems of
    >> navigational position. The material is similar to that contained in
    >> the American Nautical Almanac for 1933, but tables have been added
    >> giving the Greenwich hour angle of the Sun, Venus, Mars, Jupiter,
    >> Saturn, and 55 stars."
    >> No SHA yet. Those small extra tables gave positions in GHA. And they
    >> were given only once for each month! Tabulating the GHA of 55 stars
    >> at short intervals would have taken a huge amount of space. The
    >> solution to that problem was Sidereal hour angle. SHA Aries can be
    >> given for each hour, and  there's no need to give the SHAs of stars
    >> at short intervals. Their positions are almost constant. It's a
    >> convenient system, and takes little space.
    >> My guess is, the big shift to GHA in surface navigation didn't come
    >> until WW II. The Navy had to train a lot of navigators in a hurry.
    >> For that, GHA was the way to go. Besides being easy to teach, it was
    >> a perfect fit for  the altitude-intercept approach to position
    >> finding. That's my theory, anyway.
    >> Bruce

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