The summer solstice, the longest day of the year here in the Northern hemisphere, is marked by the sun being directly over the Tropic of Cancer (about 23.5 degrees north of the equator) at noon. The winter of solstice, here in the northern latitudes is, of course, the opposite, that time when the sun appears to have migrated south and is directly over the Tropic of Capricorn (about 23.5 degrees south of the equator) at noon.
Because of the sun’s apparent migration (actually the migration is not the sun moving but a function of the earth’s tilt and where we are on our orbit around the sun) the sun rises north of due east in summer, exactly east at the equinoxes, and south of east in the winter. But at the summer solstice, how much north of east will the sun have migrated? And will that northern migration measure out a constant angle regardless of your latitude?
I was confident during our summer solstice the sun would be 23.5 degrees north of east. You see the connection from the first paragraph right? So this morning, when I saw the sun breaching the Waterville Plateau, I grabbed a good orienteering compass that’s adjusted for declination and grabbed a measurement that would confirm my brilliance. We’re 10 days away from the solstice (which means the sun is still a tad south of its complete migration) and the Waterville Plateau is higher than the horizon so the sun would have already a moved a tad south on its daily circuit. Given these two factors, I expected my reading to be perhaps 22 or 21 degrees north of east…or a true reading of roughly 68 or 69 degrees.
During my first reading, I figured the compass must not have been flat and the needle stuck. I shook the compass and re-measured. Again, I figured the needle got stuck. After the third measurement I knew it was not a faulty compass but faulty logic at work. My reading was a true reading of 56 degrees --the sun was breaching the horizon a good 12 degrees farther north than I expect.
So who can tell me what’s going on here (in simpleton’s terms please)? Is there an easy way to calculate how much north or south of east the sun will rise at a particular latitude? And, because this probably involves more complex math than a wordsmith can assimilate, is there a good reference (chart) telling where the sun will rise on different days at different latitudes?
Please ‘comment’ to this post and shed thy wisdom.