-----Ursprüngliche Nachricht-----
Von: F.Martinelli <[EMAIL PROTECTED]>
An: [email protected] <[email protected]>
Datum: Montag, 27. September 1999 12:57
Betreff: R: Many EOT
>In Italian Nautical Astronomy we were used to distinguish between
>Equation of Mean Time and Equation of Apparent Time (in Italian we call
>Apparent Time as True Time because it is referred to the true Sun shining
in
>the sky!) .
>They are just the same numerical entity but the algebric sign is reversed
so
>that
>EqMT = - EqAT
>and viceversa.
>In such a manner following formulas always carry the (algebric) sign plus
>
>True Time = Mean Time + EqMT
>Mean Time = True Time + EaAT
>
>and were easy to be remembered by seamen.
>
Hi Franco
and all the others who are interested in this question (and they are many as
I guess).
May I add a German voice (in poor english as you can read): The history and
the situation in Germany is similar or the the same as in Italy. My
"Nautisches Jahrbuch 1973" (Nautical Almanac) I needed for my preparings for
sailing certificate has the definition "Wahre Ortszeit+
Zeitgleichung=Mittlere Ortszeit", that means "Appearent Time+EoT=Mean Time".
And just a few years later they changed it in "Mittlere Ortszeit+
Zeitgleichung= Wahre Ortszeit" ("Mean Time+EoT= Appearent Time"). As I see
the confusion is still continuing.
I wonder what the reason might be. In my opinion the different interests of
seamen and dial(l)ists might be one: For centuries for navigators it was a
question of living or dying (sometimes) to know their position on sea.
And they got it by asking the stars - and the sun, of cause.
And they got the position of stars (and sun) with the help of chronometers
(read Dava Sobel's "Longitude").
That means: They first had the Mean Time (by chronometer- Harrison) and then
got the right (appearent) position of stars and (not stripes) sun. So they
added the EoT to the Mean Time to get it.
The friens of sundials (often) go the contrary way: They know the actual
longitude-position of the sun (that indeed is Appearent Time) and need the
EoT to get Mean Time or Local Time.
If I should be wrong with my opinion please let me know it.
For all whose knowledge of German language is as poor as mine of the English
one, here are some definitions:
Wahre Ortszeit (WOZ) = Appearent Time
Mittlere Ortszeit (MOZ) = Mean Time
Gesetzliche Zeit (GZ)= Local Time (that includes daylight saving time).
Best regards
Werner
