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photoartguy
2008-Apr-17, 06:14 PM
I'm trying to find a chart or diagram that shows at what latitude the sun is perpendicular at a given date. I know there is usually one on the side of some globes (which I do not have), but I'm having trouble finding one online. Any suggestions?

aurora
2008-Apr-17, 06:46 PM
What do you mean by perpendicular?

Do you mean straight overhead at local noon?

photoartguy
2008-Apr-17, 06:54 PM
What do you mean by perpendicular? Do you mean straight overhead at local noon?

Yes. At any given date, the sun will be perpendicular at some latitude -- which will be in the southern hemisphere in the (US) winter and farther north in the summer.

Hornblower
2008-Apr-17, 06:55 PM
Try this one.
http://en.wikipedia.org/wiki/Analemma
You can enlarge the first chart by clicking on the icon in its lower right corner. For any given date, subtract 38.5209 degrees from the altitude coordinate on that date and you will get the latitude at which the noon Sun is overhead.

mugaliens
2008-Apr-17, 07:39 PM
It's a simple sinusoidal equation, with the sun being directly over the equator at the Spring and Fall equinoxes (http://en.wikipedia.org/wiki/Equinox), and approximately 23 deg above and below during it's summer peak and winter minima.

If you're into equations and charts, though, here's a good link (http://herbert.gandraxa.com/herbert/lod.asp).

photoartguy
2008-Apr-17, 09:11 PM
Great -- that's exactly what I was trying to find! I never knew the effect was call 'analemma'.

Thanks, everyone!