Given the latitude and time of year, how do I calculate the angle of the sun at any random date? For example, at 66.5°N, the angle of the sun is 0° on Dec 22, 23.5° on the equinoxes and 47° on the summer solstice. Am I correct in that the speed is not linear (ie the angle would change much faster around the equinoxes than around the solstices). What equation can I use?
2006-12-10 17:33:09 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
The particular angle you are talking about is the declination, and it is a simple sine curve, maximal at the solstices and zero at the equinoxes. Other calculations in which you might be interested are more complicated:
- The time of solar noon, when the sun is highest in the sky and directly south (or north) of you. This differs from clock noon by an amount called the equation of time; precise calculations of this are quite complex but I was able to come up with a Fourier series for it with sufficient accuracy for my application using just three terms.
- The time of sunrise and sunset. This requires doing some spherical trig with your latitude and the sun's declination, and adjusting the results with the equation of time.
- The azimuth of the sun at sunrise and sunset. See above.
2006-12-10 17:56:04 · answer #1 · answered by Anonymous · 0⤊ 0⤋
No, it's definitely not linear, and moreover, if you want to be accurate, it's affected by a LOT of things - pull from Jupiter and Saturn gravitationally, general relativistic corrections from Mercury, and so on. I would use some of the canned programs out there to do it for you - there might be a web-based one, I don't know. I use an IDL routine, but you need to have paid for the IDL license.
2006-12-10 17:37:47 · answer #2 · answered by eri 7 · 0⤊ 0⤋
The motion of the sun must be a smooth cyclical function that goes between two extrema. A sinsuoid would fit that description
2006-12-10 17:41:33 · answer #3 · answered by arbiter007 6 · 0⤊ 0⤋