GCT, Greenwich Civil Time was the older name for what is now called GMT, Greenwich Mean time.
--- On Thu, 1/31/13, Paul Dolkas <paul@dolkas.net> wrote:
From: Paul Dolkas <paul@dolkas.net> Subject: [NavList 22220] Re: Re: Re: Weems article in latest Air&Space Mag To: garylapook@pacbell.net Date: Thursday, January 31, 2013, 9:42 PM
GTC? Greenwich Computed Time? (It’s not listed anywhere in “Celestial Navigation for the Clueless”) -Paul From: NavList@fer3.com
[mailto:NavList@fer3.com] On Behalf Of Gary LaPook Sent: Wednesday, January 30, 2013 2:42 PM To: paul---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.
gl
gl
--- 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. ---------------------------------------------------------------- NavList message boards and member settings: www.fer3.com/NavList Members may optionally receive posts by
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