NavList:

   

Reply

--- "Greg R."  wrote:

> (and like I think anyone who's reduced sights manually would 
> know what they are)

Oops, I got interrupted while I was typing that and didn't catch the
omission until it had posted to the list - make that:

(and like I mentioned earlier I think anyone...)

--
GregR


--- "Greg R."  wrote:

> 
> --- 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
> > > 
> > 
> 
> 
> 
> > 
> 


--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply