NavList:

Frank wrote:

> Go to section 18 of the  Explanation. It's entitled "Sun and Moon" under
> "Auxiliary and  Planning Data"

Duh... you are so correct, thanks for the info. I had read through all of
the "Rising and Setting Phenomena" section figuring it might be included
there (we are talking about the Sun, after all...), then when they moved on
to "Altitude Correction Tables" I figured that was all they had to say for
that topic. I skimmed through the rest of the sections looking for "Equation
of Time" to have its own topic, clever of those Almanac people to hide it in
another section.  ;-)

One of these days I'm going to have to actually sit down and read the
Explanations in their entirety, lots of good info in there.

> (maybe they should include a little link that you can click on in the
> main pages  that takes you to correct section of the explanation <g>).

Heh, that would be a neat trick for a paper volume (though you may be on to
something there, when is electronic paper going to get here anyway?). For
now I'd settle for a good index - let me guess, that's probably buried
somewhere in an obscure section of the Explanations too?...  :-)

--
GregR


----- Original Message -----
From: <FrankReedCT@aol.com>
To: <NavList@fer3.com>
Sent: Wednesday, May 31, 2006 12:25 PM
Subject: [NavList 353] Re: Nautical Almac Question


>
> "Can anyone tell me why some of the "Eqn. of  Time" entries in the
Nautical
> Almanac are shaded and some are not? (A good  example is the page for June
> 12, 13 and 14 where there's an example of  both).  I'm guessing that's
> related to the Equation of Time reversing  sign (maybe the shaded entries
are
> negative?)"
>
> Yes, it's a sign  reversal. Have you ever graphed these numbers directly
from
> the almanac pages.  Maybe plot the values for the 1st and 15th of each
> month...
>
> I think  you'll find that the Explanation section of the commercial
edition
> is 100%  identical to that in the government-issued almanacs. Go to
section 18
> of the  Explanation. It's entitled "Sun and Moon" under "Auxiliary and
> Planning Data"  (maybe they should include a little link that you can
click on in the
> main pages  that takes you to correct section of the explanation <g>).
> Regarding the  equation of time, the Explanation says, "The sign is
positive for
> unshaded  values and negative for shaded values". Equivalently, the Sun is
> "early" when  the values are unshaded and "late" when shaded. You can
confirm this
> by looking  at the Sun's GHA at 12h GMT on any date. Let's take February
10. It
> varies a bit  from year to year depending on the leap year cycle, but the
EqT
> for that date is  about 14m 14s. It is shaded in the Nautical Almanac, so
the
> Sun will be late to  the meridian. When you look at the Sun's GHA at noon,
on
> the same date, you'll  find that it's 356d 26.5'. So it hasn't yet reached
> the Greenwich meridian  --it's "late". How long will it take to get there?
Well,
> it's going to have to  cover a little more than 3.5 degrees of longitude
to
> get to GHA=0. At 15 degrees  per hour, that means it will need a little
more
> than 14 minutes. And that's just  what the equation of time tells us.
>
> -FER
> 42.0N 87.7W, or 41.4N  72.1W.
> www.HistoricalAtlas.com/lunars
>
>
> >
>



--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To unsubscribe, send email to NavList-unsubscribe@fer3.com
-~----------~----~----~----~------~----~------~--~---