I am interested in determining the angle of the sun on the shortest day of the year. I know my latitude and longitude.
How do I go about computing what the lowest angle of the sun will be on the upcoming winter solstice? Thanks for your help
I am interested in determining the angle of the sun on the shortest day of the year. I know my latitude and longitude.
How do I go about computing what the lowest angle of the sun will be on the upcoming winter solstice? Thanks for your help
You mean highest?
90[sup]o[/sup] - latitude[sup]o[/sup] - 23.5[sup]o[/sup]
Sorry for the poorly constucted question. I do mean “What will be the angle of the sun above the horizon at noon on the shortest day of the year?..How do I caculate this angle if I know my latitude?”
Well, I assumed that was the question, and I’ve given you the answer.
As a bonus, the angle on the longest day is:
90[sup]o[/sup] - latitude[sup]o[/sup] + 23.5[sup]o[/sup]
At either of the equinoxes, it’s:
90[sup]o[/sup] - latitude[sup]o[/sup]
Right. Also note, this is at the sun’s apex, which is probably within an hour or so of noon, but isn’t in general, for various reasons.
“Various reasons” being time-zone width and non-circularity of orbit.
Also the tilt of the Earth’s axis.
The Equation of Time takes these last two, the eccentricity of Earth’s orbit and the tilt of Earth’s axis, into account.
Come on, Achernar, what are you talking about?
“tilt of the Earth’s axis”? That’s the fundamental thing we’re talking about.
If you want to post a detailed explanation, do so. You’re not being too helpful to the OP so far.
Oh… I’m sorry.
I didn’t know the OP wanted a detailed explanation, but I figured if you were going to go into details, they ought to be complete.
But I’m not qualified to describe it in detail. I’ll, uh, just be quiet.
If you’re less interested in figgering it all out yourself and just want an answer, a good resource is the US Naval Observatory.
Unfortunately, they seem to be down at the moment so I can’t direct you to the specific page, but you can look up the date of the winter solstice, and then get “Complete Sun and Moon Data for One Day.” The figure you’re looking for is the Sun’s elevation at noon.
[slight hijack]
If you want a fascinating hobby, sundials are pretty cool. Dover has a couple of really good books on the subject.
[/slight hijack]
Well, Achernar did say the Equation of Time, which I’m pretty sure is what you were alluding to when you mentioned the non-circularity of the Earth’s orbit. The Sun is late or early to zenith by the Equation of Time, which is graphed out at analemma.com. The two factors that influence the Equation of Time are the Earth’s elliptical orbit, and the tilt of its axis.
For instance, at Asheville NC on Feb. 2 of this year, the Sun didn’t hit the zenith until 12:44pm (and that doesn’t even involve Daylight Saving Time, which hasn’t been mentioned in this thread yet). Of that extra 44 minutes, 30 of them were due to Asheville’s longitude, which is a full half time zone width (7 1/2 degrees) west of the Eastern Time Zone center longitude, 4 of the minutes were due to the elliptical orbit, and 10 minutes were due to the tilt of the Earth’s axis.
As can be seen from the analemma.com graph, the Earth’s tilt does not make a significant difference on the dates of the four equinoxes and solstices, but Achernar was speaking in general.
Thanks for the information! So now for “high noon”, I can now get the sun angle at the summer soltice (maximum height in sky), the sun angle at the winter soltice (minimum height in sky), and the sun’s angle on the equnoxes. Very cool.
The links that were supplied were equally interesting. Thanks for those too.
(You’d think with a name like sunstone, I would know this…)