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    Re: Weems article in latest Air&Space Mag
    From: Paul Dolkas
    Date: 2013 Jan 31, 21:40 -0800

    GTC? Greenwich Computed Time? (It’s not listed anywhere in “Celestial Navigation for the Clueless”)



    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Gary LaPook
    Sent: Wednesday, January 30, 2013 2:42 PM
    To: paul@dolkas.net
    Subject: [NavList 22182] Re: Re: Weems article in latest Air&Space Mag


    That's an accurate description of it's use.
    Of course there are other ways to determine hour angle. Traditionally it was determined in time units so one did the computation of it by adding GCT and Eq.T. Navigational tables, such as Nories Haversine table (traditional navigation method), used time units for the entering argument. Even with the "new navigation" Weem's Line of Position Book, 1927 through 1943 editions also included time units for the HA entering argument (in addition to angular units.)

    It was also a common practice to carry two watches, one keeping GCT and the other adjusted to keep Greenwich Sidereal Time for star computations.



    --- On Wed, 1/30/13, Roger Connor <connorr---edu> wrote:

    From: Roger Connor <connorr---edu>
    Subject: [NavList 22165] Re: Weems article in latest Air&Space Mag
    To: garylapook---net
    Date: Wednesday, January 30, 2013, 6:07 AM

    This is how I described the Hour Angle Watch in the Time and Navigation exhibit label text:

    In the mid-1930s, the Longines-Wittnauer watch company marketed a line of watches designed in collaboration by Charles Lindbergh and P. V. H. Weems. The Hour Angle Watch sped computations for determining celestial lines of position. Its bezel and dial allowed navigators to read off the hour angle of a celestial object at Greenwich, eliminating a simple but troublesome calculation.

    BTW, I do not have a background in celestial navigation, so this exhibit has been a very interesting learning curve for me.
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