What are the right ascension and declination of the Sun at the time of the autumnal equinox?

Question

What are the right ascension and declination of the Sun at the time of the autumnal equinox?

Answer 1

Just to add a bit more to the answers you already received:

From ancient time, man needed a celestial reference for making a calendar and navigate.

The right ascension is the angle the sun makes with a reference point which is called the First Point of Aries because it was (but not anymore!) in the constellation of Aries. This is where the sun is at the spring equinox.

The ancient Babylonians measured then how many 'steps' there was in the advance of the right ascension of the sun in one year and they came with the number of 360. That was slightly wrong because the year is 365.25 days long but the figure of 360 is still used today to divide the circle in 360 degrees. Funny, isn't it? :-)

Answer 2

Assuming you mean Northern Hemisphere Autumn:

Right Ascension 12h 0m. Declination 0 degrees.

Note: the Vernal Equinox is Right Ascension 0h 0m.

Answer 3

Spring.........0h RA / 0 deg decl

Autumn......12h RA / 0 deg decl

Answer 4

0°/0°

Surprised?

Simple explanation: at the time of autumnal equinox, the sun is directly over the equator (declination 0°).

Seen from Earth, the sun is directly in the direction of the vernal equinox at that time, which is the reference direction for the RA.