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Correct - the "d" and "v" corrections (among other things) were new
items that I had to learn when I picked up celnav again a couple of
years ago and decided to join the rest of the nautical world in using
the Nautical Almanac.

--
GregR 


--- glapook@pacbell.net wrote:

> 
> Except that there are no "v" or "d" corrections with the Air Almanac
> since the period between tabulated data is only ten minutes and, to
> the accuracy of that almanac and in flight CN, there is no loss by
> ignoring such slight changes for such a short interpolation period.
> 
> gl
> 
> On Jun 19, 11:52 pm, "Greg R."  wrote:
> > --- glap...@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
> >
> > --- glap...@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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