I am worthwhile with how much you write, to exception of the following affirmation:
"Temporal hours are calculated in respect to the center of the sun as we do
for other time systems".
The hours temporarie, italic and babiloniches are reported to the sunset or
to the sunrise; the sunset and rising are, for definition, reported to the
superior limb of the Sun; therefore it is inaccurate to refer to the center of
the Sun and this yeld to an error of about 4 minutes.
Being complicated to establish the transit of the center of the Sun on the
line of the horizon is unlikely, neither it results me, that followed this
method in the antiquity when instead it is simple to refer to the superior
edge.
Best wishes, Lucio
-----Messaggio
originale-----
Da: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]Per conto di Fer J. de
Vries
Inviato: venerdì 24 settembre 2004 12.22
A: Noam
Kaplan; sundial
Oggetto: Re:
Hi Noam,
Of course the refraction effects the hourangle of
all the time systems we use in dialling.
But also keep in mind the historical meanings of
used systems as the temporal hours.
Temporal hours are calculated in respect to the
center of the sun as we do for other time systems.
The times of sunrise and sunset however are
calculated for the limb of the sun.
Should we care about that either?
We want to have time in seconds and even in
smaller parts.
But in older days the feelings about time was
much different.
Temporal hours were used as a period of time
peolple was in, not an exact moment of time as we often use.
Calculating the temporal hour lines shows that
the lines aren't straight but sligthly S-shaped which is best visible with
increasing latitude but in older dials the
lines are drawn as straight lines.
It's good to think about the effect of refraction
but in general I should say, forget the refraction in
dialling.
Best wishes, Fer.
Fer J. de Vries
----- Original Message -----
Sent: Friday, September 24, 2004 12:30
AM
Can anyone answer this?
If this is the wrong forum, I
apologize.
I have a calculation to figure out the
atmospheric refraction from Fred Sawyer's article in the NASS Compendium. It
is based on calculations that Meeus brings in his book. Refraction changes
the apparent altitude of the sun, thereby changing both the apparent
declination and apparent hour angle of the sun.
Am I making a mistake when I use the apparent
declination and apparent hour angle for the temporal hour
calculation?
The effect of a few seconds difference for
atmospheric refraction on the hour angle seems to have a much bigger
effect on the temporal hours.
Thanks for any help you can offer,
Noam
My calculations can be seen on the web at
in the function
temporal(localTime)
