[mrjesse]

Said mrjesse: I have no doubt whatsoever that the sun is apparently 20 arcseconds displaced due to the transverse velocity (sideways) of the earth as it orbits the sun. But 20 arcseconds is 0.000277777 degrees. You're talking about 2.1 degrees, which is seven thousand five hundred times bigger!

How far off is it due to the earths angular velocity?

I'm not sure whether you're talking about the earth's angular velocity as it orbits the sun or the earth's angular velocity as it rotates at 24 hours per turn. I'm also assuming that you're talking about velocity as in km/sec rather then degrees/sec.

so to answer your question: The earth orbits the sun once about every 365.24 days, which comes out to be about 1 degree per day. Thus, 1 AU * 2 * PI / 365.25 / 24 in miles = 66,627.774 miles per hour.

Due to the earth's rotation, the surface speed at the equator is (7 926.41 * PI) / 24 = 1,037.56464 miles per hour.

The formula for the angle of stellar aberration for low transverse velocities (and falling snow and the like) is about atan(transverse_velocity/speedoflight), so we see that the earth's angle of Stellar Abberation will be:

(atan(66627.774 / 670616629) / PI) * 180 = 0.00569250757 degrees, or 20.4930272 arcseconds for orbital aberration, and

(atan(1037.56464 / 670616629) / PI) * 180 = .0000886468845 degrees or about 0.319128784 arcseconds at the equator.

So you can see that that Stellar Aberration does not cause anywheres near your alleged 2.1 degrees.

-Jesse

[LeGrande]

I'm not sure whether you're talking about the earth's angular velocity as it orbits the sun or the earth's angular velocity as it rotates at 24 hours per turn.

The earths angular velocity as it rotates 24 hours per turn, of course.