Dear Gianni,
As always, you are quite right, but there
is more to say...
In all the methods to calculate or
draw sundials, geometric or analytic,
the Sun is always considered punctiform,
and reduced to its center,
Yes to all that.
...and no account is taken of
refraction...
Yes AND
From: Gianni Ferrari
Sent: November 14, 2013 9:36 AM
To: LISTA INGLESE
Subject: Re: temporal hour including refraction
No
you're right!
In all the methods
to calculate or draw sundials,
geometric or analytic, the Sun is always
considered punctiform, and reduced
to its center
Dear David,
You say, in the context of calculating solar
azimuth that...
Refraction has no effect on azimuth...
Hmmm. This is absolutely true but, alas, the
truth may well throw a beginner.
Imagine calculating the azimuth of sunrise
and going out with a friend one morning
before dawn and
Refraction affects apparent altitude at a particular time. The apparent
azimuth at a particular time does not change.
But the time of sunrise/sunset is changed due to refraction, so
therefore there is a different solar azimuth at this adjusted time.
On 2013-11-13 11:28, Frank King wrote:
I always thought that ancient dials do not take refraction into account.Am I
wrong ?Gian
Messaggio originale
Da: noa...@hotmail.com
Data: 13/11/2013 14.44
A: Sundial Listsundial@uni-koeln.de
Ogg: temporal hour including refraction
.hmmessage P
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No you're right!
In all the methods to calculate or draw sundials, geometric or analytic,
the Sun is always considered punctiform, and reduced to its center, and no
account is taken of refraction, of the lowering of the horizon (horizon
dip), of other astronomical phenomena such as parallax, etc..
