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There seems to be a number of bits and pieces of "how to calculate the Sun's position" scattered around many different articles. This article is a home for them, so we can stop cluttering up every other astronomy article with this information. Tfr000 ( talk) 17:19, 19 April 2012 (UTC)
![]() | Text and/or other creative content from Declination was copied or moved into Position_of_the_Sun. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
It was more appropriate for this article. Tfr000 ( talk) 14:53, 30 May 2012 (UTC)
![]() | Text and/or other creative content from Horizontal_coordinate_system was copied or moved into Position_of_the_Sun. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
I am putting this here for now. We already have a section very similar to this in the article. Tfr000 ( talk) 16:20, 2 July 2012 (UTC)
There are several ways to compute the apparent position of the Sun in horizontal coordinates.
Complete and accurate algorithms to obtain precise values can be found in Jean Meeus's book Astronomical Algorithms.
Instead a simple approximate algorithm is the following:
Given:
You have to compute:
where N is the number of days spent since January 1.
The article contains the following translations of its subject:
Obviously, these mean "declination", not "position". I've read the Spanish (es) one. (The Catalan is very similar.) It definitely describes the Sun's declination.
DOwenWilliams ( talk) 16:20, 24 December 2012 (UTC)
The article descibes where on the sky the sun can be found. But sun declination is a main part of this, which gives the excact latitude, at which the centre of the sun (somewhere at this latitude) currently stands in zenith position. This is always at one (and one only) signular point of the surface of the Earth. A singular point is none-dimentional and not an area. But a point that is located at a certain latitude between the tropics. Sun declination borders the equator at the equinoxes (which are excact moments, not time-periods), and tropic of cancer at northern hemisphere summer solstice (which also is a moment) , and tropic of capricorn at northern hemishpere winter solstice. The sun declination follows a sinewave (and a sinewave is a displaced cosinevawe, and reversed) whith an amplitude that eaquals the angle between the ecliptic and the equator - approx. 23.5 degrees. I belive this even is the definition of eqinoxes and solstices (?). The orbit of the Earth around the sun isn't circular, hence local noon differs between months. But - if I'm right - the sun declination isn't affected by the annual elliptic path of the Earth !? In any case this part of "position of the sun", the sun declination ought to have an article of its own, I think. It tells us at which latitude the (centre of the) sun reaches zenith. Now "sun declination" points to this page, and the issue isn't delt with. (I do not suggest that this page is wrong, just that sun declination itself is importaint enough for an article of its own) Boeing720 ( talk) 20:34, 29 August 2013 (UTC)
which can be simplified by evaluating constants to:
is wrong, first of all, one is -arcsin and the other is +arcsin? and in adittion I have tried to use both and I am getting numbers like 0.0003º when was expected around -17º.
-- 79.109.245.126 ( talk) 18:11, 12 November 2014 (UTC)
The J2000.0 value for the ecliptic longitude of the Earth λE is from the Explanatory Supplement to the Astronomical Almanac. Δt is the elapsed time from the start of the year 2000. The maximum error found for the longitude, λ, was about 1.5 minutes of arc. -- Jbergquist ( talk) 21:21, 28 January 2016 (UTC)
The mean motion, n, is strictly speaking an angular velocity so one would expect it to be expressed in ° per unit time or radians per unit time but the product nΔt is just an angle and the article expresses product as the mean daily angular change and the number of days and fractions thereof if necessary. The correction for aberration is about 20 arc seconds or less and has a sinusoidal dependence on the longitude and the light time from the Sun also has an annual variation. The formulas for longitude and declination don't appear to be corrected for changes in the position of the vernal equinox. These corrections aren't necessary if one is working at the level of 1 minute of arc accuracy. -- Jbergquist ( talk) 17:44, 29 January 2016 (UTC)
I've been trying to figure out how to best use Cooper's relationship for declination. In this article it is reported as:
even if in Cooper's original paper (The absorption of radiation in solar stills, 1969) is:
In particular, I was wondering what N=0 meant. What instant does it represent? In this article it's written N=0 is midnight UTC between December 31st and January 1st. In Cooper's original paper is only written: "convenient approximate relationship for solar declination in terms of the day of the year n (i.e. 1st or 200th)".
I personally tried to do some calculations and I think the best thing would be to consider N=1 as the noon UTC on January 1st. I believe this minimizes the error.
Also, however, don't you think that instead of "overestimates", "underestimates" should go? You could have a look here https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle
Sam X ( talk) 21:50, 11 May 2020 (UTC)
The article has a bad link --> http://asa.usno.navy.mil/SecK/2013/Astronomical_Constants_2013.pdf
Some of it is good. This may be the best place for the topic to start. http://asa.usno.navy.mil/
All that is needed here is either delete the bad one or see if it has been moved.
While doing any changes take a look at http://www.iausofa.org/
Programmers might be interested is this last one.
Another Missing Link: The link to reference 11 does not work. — Preceding
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82.37.54.83 (
talk) 07:32, 2 June 2016 (UTC)
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I think the light weirdness makes very roughly about 20 angle seconds lag in where the sun is seen to be from where it really is. Such things are not talked about here. 121.127.214.82 ( talk) 15:47, 27 December 2022 (UTC)
Okay, I found Aberration of light#Solar annual aberration also gives ~20 angle seconds, so will add that to end of this one. 121.127.212.32 ( talk) 05:05, 18 February 2023 (UTC)
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There seems to be a number of bits and pieces of "how to calculate the Sun's position" scattered around many different articles. This article is a home for them, so we can stop cluttering up every other astronomy article with this information. Tfr000 ( talk) 17:19, 19 April 2012 (UTC)
![]() | Text and/or other creative content from Declination was copied or moved into Position_of_the_Sun. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
It was more appropriate for this article. Tfr000 ( talk) 14:53, 30 May 2012 (UTC)
![]() | Text and/or other creative content from Horizontal_coordinate_system was copied or moved into Position_of_the_Sun. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
I am putting this here for now. We already have a section very similar to this in the article. Tfr000 ( talk) 16:20, 2 July 2012 (UTC)
There are several ways to compute the apparent position of the Sun in horizontal coordinates.
Complete and accurate algorithms to obtain precise values can be found in Jean Meeus's book Astronomical Algorithms.
Instead a simple approximate algorithm is the following:
Given:
You have to compute:
where N is the number of days spent since January 1.
The article contains the following translations of its subject:
Obviously, these mean "declination", not "position". I've read the Spanish (es) one. (The Catalan is very similar.) It definitely describes the Sun's declination.
DOwenWilliams ( talk) 16:20, 24 December 2012 (UTC)
The article descibes where on the sky the sun can be found. But sun declination is a main part of this, which gives the excact latitude, at which the centre of the sun (somewhere at this latitude) currently stands in zenith position. This is always at one (and one only) signular point of the surface of the Earth. A singular point is none-dimentional and not an area. But a point that is located at a certain latitude between the tropics. Sun declination borders the equator at the equinoxes (which are excact moments, not time-periods), and tropic of cancer at northern hemisphere summer solstice (which also is a moment) , and tropic of capricorn at northern hemishpere winter solstice. The sun declination follows a sinewave (and a sinewave is a displaced cosinevawe, and reversed) whith an amplitude that eaquals the angle between the ecliptic and the equator - approx. 23.5 degrees. I belive this even is the definition of eqinoxes and solstices (?). The orbit of the Earth around the sun isn't circular, hence local noon differs between months. But - if I'm right - the sun declination isn't affected by the annual elliptic path of the Earth !? In any case this part of "position of the sun", the sun declination ought to have an article of its own, I think. It tells us at which latitude the (centre of the) sun reaches zenith. Now "sun declination" points to this page, and the issue isn't delt with. (I do not suggest that this page is wrong, just that sun declination itself is importaint enough for an article of its own) Boeing720 ( talk) 20:34, 29 August 2013 (UTC)
which can be simplified by evaluating constants to:
is wrong, first of all, one is -arcsin and the other is +arcsin? and in adittion I have tried to use both and I am getting numbers like 0.0003º when was expected around -17º.
-- 79.109.245.126 ( talk) 18:11, 12 November 2014 (UTC)
The J2000.0 value for the ecliptic longitude of the Earth λE is from the Explanatory Supplement to the Astronomical Almanac. Δt is the elapsed time from the start of the year 2000. The maximum error found for the longitude, λ, was about 1.5 minutes of arc. -- Jbergquist ( talk) 21:21, 28 January 2016 (UTC)
The mean motion, n, is strictly speaking an angular velocity so one would expect it to be expressed in ° per unit time or radians per unit time but the product nΔt is just an angle and the article expresses product as the mean daily angular change and the number of days and fractions thereof if necessary. The correction for aberration is about 20 arc seconds or less and has a sinusoidal dependence on the longitude and the light time from the Sun also has an annual variation. The formulas for longitude and declination don't appear to be corrected for changes in the position of the vernal equinox. These corrections aren't necessary if one is working at the level of 1 minute of arc accuracy. -- Jbergquist ( talk) 17:44, 29 January 2016 (UTC)
I've been trying to figure out how to best use Cooper's relationship for declination. In this article it is reported as:
even if in Cooper's original paper (The absorption of radiation in solar stills, 1969) is:
In particular, I was wondering what N=0 meant. What instant does it represent? In this article it's written N=0 is midnight UTC between December 31st and January 1st. In Cooper's original paper is only written: "convenient approximate relationship for solar declination in terms of the day of the year n (i.e. 1st or 200th)".
I personally tried to do some calculations and I think the best thing would be to consider N=1 as the noon UTC on January 1st. I believe this minimizes the error.
Also, however, don't you think that instead of "overestimates", "underestimates" should go? You could have a look here https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle
Sam X ( talk) 21:50, 11 May 2020 (UTC)
The article has a bad link --> http://asa.usno.navy.mil/SecK/2013/Astronomical_Constants_2013.pdf
Some of it is good. This may be the best place for the topic to start. http://asa.usno.navy.mil/
All that is needed here is either delete the bad one or see if it has been moved.
While doing any changes take a look at http://www.iausofa.org/
Programmers might be interested is this last one.
Another Missing Link: The link to reference 11 does not work. — Preceding
unsigned comment added by
82.37.54.83 (
talk) 07:32, 2 June 2016 (UTC)
Hello fellow Wikipedians,
I have just modified 2 external links on Position of the Sun. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
This message was posted before February 2018.
After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than
regular verification using the archive tool instructions below. Editors
have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the
RfC before doing mass systematic removals. This message is updated dynamically through the template {{
source check}}
(last update: 5 June 2024).
Cheers.— InternetArchiveBot ( Report bug) 20:52, 22 May 2017 (UTC)
I think the light weirdness makes very roughly about 20 angle seconds lag in where the sun is seen to be from where it really is. Such things are not talked about here. 121.127.214.82 ( talk) 15:47, 27 December 2022 (UTC)
Okay, I found Aberration of light#Solar annual aberration also gives ~20 angle seconds, so will add that to end of this one. 121.127.212.32 ( talk) 05:05, 18 February 2023 (UTC)