September equinox

[7] The September equinox is one point in time commonly used to determine the length of the tropical year.

The solar point of the September equinox passed from Libra and into Virgo in −729 (730 BCE) and will enter Leo in 2439.

For viewers at the north or south poles, it moves virtually horizontally on or above the horizon, not obviously rising or setting apart from the movement in "declination" (and hence altitude) of a little under a half (0.39) degree per day.

For observers in either hemisphere not at the poles, the Sun rises and sets more and more to the south during the 3 months following the September equinox.

This period is the second half of a 6-month long southerly movement, beginning with the June solstice when the Sun rises and sets at its most northern point.

Illumination of Earth by the Sun on the day of an equinox
Sunset at the equinox from the site of Pizzo Vento at Fondachelli Fantina , Sicily