| Topic: |
Science > Physics |
| User: |
"masa" |
| Date: |
05 Sep 2005 07:19:42 AM |
| Object: |
Rise and fall of the sun |
Hi!
I have a question that I have not found an answer to during my studies
at university...
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
BR
Masa
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| User: "Bruce Scott TOK" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 09:17:20 AM |
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I have a question that I have not found an answer to during my studies
at university...
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
This is actually quite a difficult calculation if you do it
analytically. Length of day as a function of latitude. Obviously
longitude doesn't enter unless you include the effect of being off
center in a given time zone on the sunrise and sunset times.
You'll probably end up with a program of some sort (I did this ages ago
but no chance of digging up the notes).
--
ciao,
Bruce
drift wave turbulence: http://www.rzg.mpg.de/~bds/
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| User: "" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 01:38:50 PM |
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This is actually quite a difficult calculation if you do it
analytically. Length of day as a function of latitude. Obviously
longitude doesn't enter unless you include the effect of being off
center in a given time zone on the sunrise and sunset times.
It's a little more complicated than one being away from the time zone's
central meridian. The Earth's orbit is an ellipse and thus the sun's
annual motion against the celestial sphere is not uniform, so we have
to keep time by a ficticious mean sun that does travel uniformly around
the sky. It's called the equation of time correction, and it's given
by the analemma, the figure 8 on many old globes out in the Pacific. I
heard that it was taken off modern globes becase teachers were
embarassed when students asked about it, and the teacher didn't have a
clue.
PS - I opened this thread because I thought it would deal with solar
evolution, you know, how all the Earth's oceans will be boiled away by
1,000,000,000 A911, but this topic is ok too.
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| User: "Uncle Al" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 06:45:04 PM |
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masa wrote:
Hi!
I have a question that I have not found an answer to during my studies
at university...
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
Remember that the physcial circumstance is altered by the atmosphere's
refraction at long pathlengths. Physical sunset and sunrise vs.
visible sunset and sunrise have about quarter-hour offsets.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "Herman Trivilino" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 08:44:11 PM |
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masa wrote:
I have a question that I have not found an answer to during my studies
at university...
Why?
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
Sounds like a homework assignment a friend of mine had when we were in
college. He never found the formula, either.
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| User: "Bruce Scott TOK" |
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| Title: Re: Rise and fall of the sun |
06 Sep 2005 09:28:52 AM |
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Sounds like a homework assignment a friend of mine had when we were in
college. He never found the formula, either.
You can relatively readily get the latitude versus length of day but it
is in the form of an integral over transcendental functions and doesn't
look possible to invert. I might be remembering this wrong though.
--
ciao,
Bruce
drift wave turbulence: http://www.rzg.mpg.de/~bds/
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| User: "" |
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| Title: Re: Rise and fall of the sun |
06 Sep 2005 04:54:42 AM |
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In article <1125971202_6985@spool6-east.superfeed.net>,
"Herman Trivilino" <physhead@kingwoodREMOVECAPScable.com> wrote:
masa wrote:
I have a question that I have not found an answer to during my studies
at university...
Why?
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
Sounds like a homework assignment a friend of mine had when we were in
college. He never found the formula, either.
I am not doing homework. :-)
Could the prediction be done using a well-placed pendulum?
I'm thinking about the one in Chicago's Museum of Science
and Industry. Could the points of rising and setting be
a pair of pegs in that circle?
/BAH
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| User: "Richard Henry" |
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| Title: Re: Rise and fall of the sun |
06 Sep 2005 09:36:28 AM |
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<jmfbahciv@aol.com> wrote in message
news:dfjp12$8qk_007@s901.apx1.sbo.ma.dialup.rcn.com...
In article <1125971202_6985@spool6-east.superfeed.net>,
"Herman Trivilino" <physhead@kingwoodREMOVECAPScable.com> wrote:
masa wrote:
I have a question that I have not found an answer to during my studies
at university...
Why?
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
Sounds like a homework assignment a friend of mine had when we were in
college. He never found the formula, either.
I am not doing homework. :-)
Could the prediction be done using a well-placed pendulum?
I'm thinking about the one in Chicago's Museum of Science
and Industry. Could the points of rising and setting be
a pair of pegs in that circle?
No.
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| User: "masa" |
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| Title: Re: Rise and fall of the sun |
08 Sep 2005 05:21:47 AM |
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No it is deinetly not a homework assignment since it=B4s about 15 years
ago that I took my MSc. And it was in engineering, alas, not physics...
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| User: "Sam Wormley" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 07:44:51 AM |
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masa wrote:
I would like to obtain a formula for calculating the time of sun rising
over the horison and falling down the horison. All this given lat. and
long. for the point of view.
Resources:
PRACTICAL ASTRONOMY WITH YOUR CALCULATOR, 3rd edition
by Peter Duffett-Smith
Cambridge University Press, Cambridge 1988
QB47 522'.028'54
ISBN 0 521 35699 7 ppk
ASTRONOMICAL ALGORITHMS
by Jean Meeus
Willmann-Bell, Inc., P.O. Box 35025, Richmond, Virginia 23235 1991
QB51.3.E43M42 1991 520-dc20 91-23501 CIP
EXPLANATORY SUPPLEMENT TO THE ASTRONOMICAL ALMANAC
Edited by P. Kenneth Seidelmann, U.S. Naval Observatory, Washington D.C.
University Science Books Mill Valley, CA 94941 1992
Library of Congress Catalog Number: 91-65331
ISBN 0-935702-68-7
Sunrise/Sunset Algorithm
http://williams.best.vwh.net/sunrise_sunset_algorithm.htm
Astronomical Algorithms, Calculations & Software
http://www.edu-observatory.org/eo/algorithms.html
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| User: "masa" |
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| Title: Re: Rise and fall of the sun |
05 Sep 2005 08:40:37 AM |
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Thank You very much
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