2026, September 22: Autumnal Equinox 2026: Daylight, the Ecliptic, and the Harvest Moon Effect

September 22, 2026: The autumnal equinox occurs today. Learn why daylight and darkness are not exactly equal, how the ecliptic changes angle with the horizon, and why the Harvest Moon rises at nearly the same time each evening.

Sunrise approaches
Photo Caption – Sunrise approaches, July 3, 2022.

by Jeffrey L. Hunt                                                

Chicago, Illinois: Sunrise, 6:38 a.m. CDT; Sunset, 6:48 p.m. CDT.  Times are calculated by the US Naval Observatory’s MICA computer program. Check local sources for sunrise and sunset times.

Venus as an Evening Star

Autumnal Equinox

black and gray desk globe
Photo Caption – Earth Globe (Photo by lilartsy on)

The autumnal equinox occurs today at 7:05 p.m. Central Time. At this time, the sun’s light is most direct at the equator, passing overhead at local noon. After today, the sun’s direct rays are south of the equator until March 20, 2027, at the next vernal equinox.

Frequently, we state that daylight and darkness are equal on this date. In the way sunrise and sunset are defined, Chicago’s daylight spans 12 hours, 10 minutes, compared to 12 hours, 8 minutes in Miami. In Anchorage, the sun is in the sky for 12 hours, 14 minutes. South of the equator, in Auckland, daylight lasts 12 hours, 8 minutes, compared to 12 hours, 9 minutes in Nashville. Both cities are nearly equidistant from the equator. In Auckland, daylight and darkness were equal three days ago.

Daylight is longer than 12 hours because the atmosphere bends sunlight and sunrise and sunset are timed from the sun’s upper edge rather than its center. While the equinox marks a balance point in the sun’s annual motion, daylight and darkness are not exactly 12 hours long on this date.

Celestial Longitude

Autumnal Equinox is the intersection of the ecliptic and the celestial equator, marking the spot where the sun’s rays begin to shine more directly in the southern hemisphere.
Chart Caption – Autumnal Equinox is the intersection of the ecliptic and the celestial equator, marking the spot where the sun’s rays begin to shine more directly in the southern hemisphere.

As for the equinox, the sun reaches celestial longitude 180°, halfway through its annual circuit that begins at the vernal equinox in late March each year. For simplicity, sky watchers frequently use the sun’s perceived motion to describe seasonal changes, rather than referring directly to Earth’s motions. Sunrise and sunset are commonly used to describe the sun’s daily appearance in the east and disappearance in the west, although those motions result from Earth’s rotation.

Earth’s annual revolution around the sun is mirrored in the sun’s perceived motion along the ecliptic, the plane of the solar system. The ecliptic serves as a coordinate system for the motions of the planets and moon. Celestial longitude is measured eastward along the ecliptic from the vernal equinox point. With the sun at 0° celestial latitude, meaning it is on the ecliptic, and at celestial longitude 180°, it appears in front of Virgo, signaling the equinox.

On September 1, a Venus–Spica conjunction occurred. Spica is Virgo’s brightest star. It is at solar conjunction on October 17.

Seasons

Spring flowering trees
Photo Caption – Spring flowering trees

The equinoxes and solstices mark the beginnings of the astronomical seasons and are points on the ecliptic coordinate system. At sunrise on today’s equinox, the autumnal equinox point is on the eastern horizon, the summer solstice point is in the south, and the vernal equinox point is on the western horizon. The ecliptic makes a steep angle with both horizons. To see this, trace an imaginary line from Jupiter to Mars before sunrise.

At sunset, the equinox points are reversed and the winter solstice point is in the south. The ecliptic makes a shallow angle with both horizons. This is seen in Venus’ low altitude in the west-southwest during evening twilight. During evening twilight, Venus highlights the shallow angle of the ecliptic after sunset.

Harvest Moon Effect

Moon, September 19-23, 2026
Chart Caption – 2026, September 19-23: The waxing moon is in the southern sky appears farther eastward in front of Sagittarius and Capricornus.

The Harvest Moon Effect results from autumn’s shallow ecliptic angle. During this time of year, the moon’s altitude changes little from night to night around the Full Moon, although it appears farther eastward along the horizon. This causes the moon to rise only a short time later each evening near the Harvest Moon.

It is the autumnal equinox. Daylight continues to shorten across the Northern Hemisphere.

Enjoy the new season.

For our Southern Hemisphere readers, Happy Spring!

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