Mashallah,
I believe you are correct about azimuth and time of transit being unaffected by
refraction.
"Astronomical Algorithms" by Jean Meeus has a good section on calculating
effects of refraction and the sun's semi-diameter. Also a valuable section
about how to correct for the effects of Nutation. I'm not so sure about the
other topics you mention. I would guess parallax of the sun from the
perspective of the earth's diameter is covered in surveying books, or perhaps
one of the astronomical trigonometry books by Smart.
-Bill Gottesman
----- Original Message -----
From: Mashallah Ali-Ahyaie
To: sundial@uni-koeln.de
Sent: Thursday, December 27, 2007 4:24 AM
Subject: Does Refraction Affect Azimuth? / Re: sundial Digest, Vol 24, Issue
17
Dear Mr Gianni Ferrari,
Greetings, happy new year and Merry Christmas to you and all members.
As I recall, the azimuth of a body and its time of transit are not
affected by refraction. Please kindly do comment.
Also, I would like to have a good and applied article on astronomical
corrections (Refraction, Parallax, Dip of Horizon and Semi-Diameter.) I wonder
if any respectful member could help.
Best regards,
Mashallah Ali-Ahyaie
On Dec 26, 2007 2:30 PM, <[EMAIL PROTECTED]> wrote:
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Message: 1
Date: Tue, 25 Dec 2007 22:58:32 +0100 (GMT+01:00)
From: " [EMAIL PROTECTED]" <[EMAIL PROTECTED]>
Subject: R: Re: Azimuth of Sunrise - Sunset
To: <sundial@uni-koeln.de >
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And the air refraction ?
Because of refraction, the sun is already
below the horizon when we observe
the upper limb kiss the horizon. In
this moment the altitude of the Sun?s center is about
?(34+14) = -48?
(the refraction at 0? degree is about 34?)
The Azimuth of the point
where we begin to see the Sun (limb) is then different from the
theoretical and geometrical value, also if the differences are small at
mean latitudes.
With Lat = 45 on Winter Solstice, the Azimut of the
Sun?s limb (when it appears) is about 56.8 degree ; the Azimuth of the
Sun?s center 56.4? and the theoretical Azimuth 55.8?.
The differences
increase when Latitude increases.
With Lat.= 66?. the Sun?s limb
appears with an Azimuth about 7 degree more than the theoretical value
(18.8 and 11.9?)
My best wishes for a sunny New Year !
Gianni Ferrari
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End of sundial Digest, Vol 24, Issue 17
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--
Mashallah Ali-Ahyaie
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