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--- glapook@pacbell.net wrote:

> "v, the difference between the actual change in GHA in one hour and a
> constant value used in the interpolation tables; and d, the change in
> declination in one hour."

Right, those tell what "v" and "d" are (and like I think anyone who's
reduced sights manually would know what they are) - but my original
question was what actual words the letters are abbreviations for.

BTW, I originally learned celnav with the Air Almanac (way back in the
mid-70s - at the time it looked "easier" than using the Nautical
version), but I'd be totally lost if I had to use it now...  ;-)

--
GregR



--- glapook@pacbell.net wrote:



> 
> Look at article 1903 in Bowditch, available here:
> 
>
http://www.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-19.pdf
> 
> "v, the difference between the actual change in GHA in one hour and a
> constant value used in the interpolation tables; and d, the change in
> declination in one hour."
> 
> gl
> 
> On Jun 19, 10:41 pm, glap...@pacbell.net wrote:
> > Here are excerpts from the 1937 N.A The first page shows the time
> of
> > transit of the moon of the Greenwich meridian and contains a "Var.
> per
> > hour" column, variation?, the change in declination inone hour."
> >
> > http://www.geocities.com/fredienoonan/almanac-1937-136.JPG
> >
> > The second page contains moon data showing GHA and DEC and has
> > separate increments tables for each day based on the the dec change
> > and GHA change rates for that particular day. no "v" or "d"
> correction
> > factors are shown.
> >
> > http://www.geocities.com/fredienoonan/almanac.html
> >
> > This third link takes you to a site I put up with with excerpts of
> > various navigation texts.
> >
> > http://www.geocities.com/fredienoonan/
> >
> > gl
> >
> > On Jun 19, 9:00 pm, frankr...@HistoricalAtlas.net wrote:
> >
> > > Greg, you asked:
> > > "And maybe that's going to be about as good an answer as we can
> hope for
> > > at this point in time - does anyone know when "d" and "v" terms
> first
> > > showed up in the NA as such? There might be more elaboration
> about what
> > > the abbreviations stood for when they were first introduced."
> >
> > > Yes, that's basically what I was providing you in the previous
> message. The
> > > labels "v" and "d" first appear in the "Abridged Nautical
> Almanac" in 1952.
> > > This is the earliest date when the official British almanac
> included GHA.
> > > This had been introduced 18 years earlier in the American
> Nautical Almanac,
> > > and it was also widely used in the various air almanacs. As I
> said, the
> > > concept of the interpolation constant at the foot of each column
> on the
> > > almanac page was already present in the American almanac where it
> was called
> > > a "code". I also checked a couple of commercial British almanacs
> from this
> > > period (the commercial British almanacs adopted GHA well before
> the official
> > > British almanac). They use a similar principle but again not
> labeled v and
> > > d. So my best guess right now is that the first use of these
> specific labels
> > > for the interpolation data is the British "Abridged Nautical
> Almanac" in
> > > 1952. Here's the full text from the explanation in the AbNA for
> 1953:
> > >  "Interpolation between the tabulated hourly values is provided
> for by
> > > comprehensive interpolation tables, printed on coloured pages at
> the end of
> > > the book, giving for every minute and every second the increments
> of G.H.A.
> > > corresponding to the mean rate of increase for the Sun (15�
> precisely), the
> > > constant rate for Aries (15� 02'.46) and the minimum rate for the
> Moon (14�
> > > 19'.0). The variations from the means are so small for the Sun
> that they
> > > have been deliberately ignored; the tabulated hourly values of
> the Sun's
> > > G.H.A. have been adjusted so that the error thus caused is a
> minimum. These
> > > variations cannot be ignored for the planets or for the Moon, and
> > > corrections have to be made for the excess (v) in hourly motion
> over that
> > > adopted in the main interpolation tables."
> >
> > > So there's an answer: v stands for "excess". :-)
> >
> > > In the next paragraph:
> > > "The corrections for these VARIATIONS [...] are taken directly
> from the
> > > interpolation tables with argument v" and "A similar procedure is
> used to
> > > interpolate the declinations of the Sun, Moon and planets; here
> d, the
> > > hourly DIFFERENCE, is given without sign on the daily pages" (I
> have
> > > capitalized those two words for emphasis). So if you must assign
> a meaning
> > > to v and d, I think the best bets are "variation" (of the rate of
> change of
> > > GHA from the selected mean rate) and "difference," but the catch
> is that the
> > > person who wrote this explanatory section may very well have
> invented those
> > > origins on the spot.
> >
> > > By 1958, when the modern Nautical Almanac was formed by the
> merger of the
> > > American Nautical Almanac and the Abridged Nautical Almanac (they
> kept their
> > > separate names until 1960), the explanation simply refers to v
> and d values
> > > with no hint of any etymology. Same in Bowditch of the same era.
> I think
> > > this is intentional. The labels v and d really are not intended
> to "stand
> > > for" anything.
> >
> > >  -FER
> > 
> 



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