NavList:

   

Reply

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