3 ms·

I've never heard the term "solar north" used that way before. It seems like you're defining it as 90 degrees left of the point of sunrise, but that seems arbit

I've never heard the term "solar north" used that way before. It seems like you're defining it as 90 degrees left of the point of sunrise, but that seems arbitrary -- why not define it as 90 degrees to the right of sunset instead? And if you try to resolve this ambiguity by defining it as the midpoint between sunrise and sunset, then that's just the same as true north. The sunrise and sunset points are closer together in summer and farther apart in winter, but true north is always halfway between them. (Well, there's a very slight seasonally-dependent error, due to the fact that the sun is at slightly different latitudes when observed 12-ish hours apart. But on average it's exactly the same.)

TeMPOraL 4y ago
Ok, what about the "orbital north" then? As in one of the two points on the surface intersected by a line that goes through the very center of Earth and is perpendicular to the Earth's orbital plane. (Or maybe let's call it "normal north", since the line is along the normal vector of the orbital plane.)
- teraflop 4y ago
  "Orbital north", a.k.a. the north ecliptic pole, isn't really something that makes sense to plot on a map. It's a three-dimensional vector that points in the direction of the northern constellation Draco. So when viewed from the perspective of an observer on the Earth's surface, it appears to trace out a circle in the sky (centered on Polaris) every 23 hours and 56 minutes, as the Earth rotates under it. I suppose if you want, you could calculate the projection of that vector onto a local tangent plane to the Earth's surface at a particular instant in time, and translate that to a compass direction. It would point somewhere between NNW and NNE, depending on your latitude, time of year, and time of day. (If I'm visualizing it correctly, it ought to point due north at local noon on the summer and winter solstices.)

TeMPOraL 4y ago

Ok, what about the "orbital north" then? As in one of the two points on the surface intersected by a line that goes through the very center of Earth and is perpendicular to the Earth's orbital plane. (Or maybe let's call it "normal north", since the line is along the normal vector of the orbital plane.)

teraflop 4y ago
"Orbital north", a.k.a. the north ecliptic pole, isn't really something that makes sense to plot on a map. It's a three-dimensional vector that points in the direction of the northern constellation Draco. So when viewed from the perspective of an observer on the Earth's surface, it appears to trace out a circle in the sky (centered on Polaris) every 23 hours and 56 minutes, as the Earth rotates under it. I suppose if you want, you could calculate the projection of that vector onto a local tangent plane to the Earth's surface at a particular instant in time, and translate that to a compass direction. It would point somewhere between NNW and NNE, depending on your latitude, time of year, and time of day. (If I'm visualizing it correctly, it ought to point due north at local noon on the summer and winter solstices.)