I've been getting very confused about which direction is actually south. I need this for determining how solar panels will face. The problem is not which direction they should face (I've read articles about that, the answer is that optimally they should tilt south at some angle determined by latitude, and I've seen calculators for determining angle but still thinking about that part), but which direction is actually south.
I figured the ultimate measure of south would be 90 degrees from west, and west is where the sun sets, right? I didn't trust my cheap compass because of magnetic declination and possibly bias from local magnets. I don't trust my housing tract layout either.
My latitude is about 29.5 degrees north, and the description below applies to those in the mid northern hemisphere (like continental USA).
It turns out that where the sun sets depends on the time of year (and latitude). Basically, the sun rises in the southeast and sets in southwest...IN THE WINTER (or around winter solstice). In the summer, the sun rises in the northeast and sets in the northwest. In either case, it basically makes an arc across the sky, so at midday it is always at some southerly angle. So to add to the wierdness, in the late afternoon around the summer solstice, the sun appears to be traveling almost north, since it is moving away from the southern angle it had at midday.
Here is a convenient calculator which made this clear to me.
When does the sun rise exactly in the east and set exactly in the west? Well, that's twice a year, during the Vernal and Autumnal equinoxes.
The axial tilt of the earth is 23.4 degrees. That suggests that on midday around the summer solstice the angle of the sun southward is a mere 6.1 degrees from straight up vertical here at 29.5 degrees longitude, because the axial tilt is mostly canceling the latitude. In winter, the two add up so the sun would be 52.9 degrees southward from vertical. And that goes a long way toward explaining why solar panel is supposed to be tilted a mere 30 degrees up from horizontal, though it still seems pretty weird.
Strange considering how important the sun is, how little close attention I've actually paid to it.
I figured the ultimate measure of south would be 90 degrees from west, and west is where the sun sets, right? I didn't trust my cheap compass because of magnetic declination and possibly bias from local magnets. I don't trust my housing tract layout either.
My latitude is about 29.5 degrees north, and the description below applies to those in the mid northern hemisphere (like continental USA).
It turns out that where the sun sets depends on the time of year (and latitude). Basically, the sun rises in the southeast and sets in southwest...IN THE WINTER (or around winter solstice). In the summer, the sun rises in the northeast and sets in the northwest. In either case, it basically makes an arc across the sky, so at midday it is always at some southerly angle. So to add to the wierdness, in the late afternoon around the summer solstice, the sun appears to be traveling almost north, since it is moving away from the southern angle it had at midday.
Here is a convenient calculator which made this clear to me.
When does the sun rise exactly in the east and set exactly in the west? Well, that's twice a year, during the Vernal and Autumnal equinoxes.
The axial tilt of the earth is 23.4 degrees. That suggests that on midday around the summer solstice the angle of the sun southward is a mere 6.1 degrees from straight up vertical here at 29.5 degrees longitude, because the axial tilt is mostly canceling the latitude. In winter, the two add up so the sun would be 52.9 degrees southward from vertical. And that goes a long way toward explaining why solar panel is supposed to be tilted a mere 30 degrees up from horizontal, though it still seems pretty weird.
Strange considering how important the sun is, how little close attention I've actually paid to it.
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