Originally Posted by watha
the sun can't always be to the south of you in the northern hemisphere, because during summer, the earth's axial tilt causes us to "lean forward," and the sun would consequently be north of the equator, so portions of the northern hemisphere must be south of the sun's track. At least, I think that's right.
Correct. The sun is north of an observer on the equator when the sun's declination is north of the equator in the northern hemisphere from spring equinox to autumn equinox because of the inclination of the ecliptic (path of the sun through the sky) relative to the equator (23.4 degree tilt of the earth's axis relative to the sun).
This explains why the sun's declination (angular north/south distance from the equator) varies from 23.4 deg N to 23.4 deg S throughout the year, making the sun appear to move above and below the equator as the seasons progress. The sun moves northerly or southerly at about 1 knot
during the two equinox periods (summer or winter), when declination is changing the fastest.
So, the sun is north of the observer (or sun-bather) in the northern hemisphere any time between the spring and autumn equinoxes when the observer is south of the sun's declination.
A navigator has to take declination into account when reducing a noon sun sextant
sight to measure latitude.
Take a navigator on the equator (00deg 00.0'N) at longitude 064deg 0.00'W, on June 21, 2010 close to summer solstice, when the sun is as far north as it gets:
On that date and at that location, high noon was 13h17m48s DST. The sun was at an altitude of 66 degrees above the horizon, due north of the navigator. A person on land could have told us the sun was due north by looking at a sundial, but that device does not work well on a rolling boat, so the navigator at sea has to calculate the direction of the sun using sextant
altitudes and tables of data. Or today's navigators can look at a computer with a GPS antenna
attached to it to see where the sun lies relative to the boat.
On that near-solstice date at 1900 hours (7 PM) DST, the sun was about 4 degrees above the horizon and setting rapidly toward sunset at 1922, bearing 293.5 degrees from the navigator, or 23.5 degrees north of due west. Which makes sense, because the sun sets on the latitude of its declination north of the equator, and the declination on that date was almost 23.5 degrees north.
However, check this information with another source before relying on it. Hopefully someone else will step in to comment if I have mis-stated something.