Autumn Night Sky: What to Observe

Autumn brings crisp, clear nights and a sky filled with mythological characters. The Summer Triangle lingers in the west while new patterns rise in the east. Autumn's signature attraction is the Great Square of Pegasus, a large, distinctive pattern that anchors a family of constellations connected by an ancient Greek myth. This is also the best time to observe our nearest galactic neighbor, the Andromeda Galaxy.

Key Autumn Constellations

Pegasus

The Great Square of Pegasus is the season's primary signpost -- four moderately bright stars forming a large square high in the south during autumn evenings. Despite its size, the interior of the square is notably empty of bright stars, making it easy to identify.

Andromeda

Extending from the northeast corner of the Great Square, Andromeda is a chain of stars that leads to one of the sky's greatest treasures: the Andromeda Galaxy (M31). This is the nearest large galaxy to the Milky Way, visible to the naked eye from dark sites as an elongated smudge of light. Through binoculars, it reveals its bright core and extended disk.

Cassiopeia

High in the north, Cassiopeia's distinctive W (or M) shape is a circumpolar constellation visible year-round but at its most prominent in autumn. It sits across Polaris from the Big Dipper and lies within a rich section of the Milky Way.

Perseus

Between Cassiopeia and Taurus, Perseus contains the famous variable star Algol (which dims noticeably every 2.87 days as a companion star eclipses it) and the beautiful Double Cluster -- two open star clusters side by side, magnificent in binoculars.

Cetus the Whale

A large, faint constellation below Pisces. Cetus contains Mira, a famous long-period variable star that ranges from naked-eye brightness to invisibility over about 11 months.

Aquarius and Pisces

These zodiac constellations are faint and spread out but contain the ecliptic, so planets frequently pass through them. Check planet positions to see if any planets are brightening these regions.

Autumn Deep-Sky Highlights

• M31 (Andromeda Galaxy): The premier autumn deep-sky object. At 2.5 million light-years away, it is the most distant thing visible to the naked eye. Binoculars reveal its elongated glow spanning several degrees.
• M33 (Triangulum Galaxy): A face-on spiral galaxy near Andromeda. Fainter and more diffuse than M31, it requires dark skies but can be spotted in binoculars.
• NGC 869/884 (Double Cluster): Two adjacent open clusters in Perseus. One of the finest sights in the sky through binoculars -- hundreds of stars sparkling in two tight groups.
• M15: A bright, compact globular cluster in Pegasus. Easily found with binoculars.
• NGC 7293 (Helix Nebula): A large, faint planetary nebula in Aquarius. Challenging but rewarding from dark sites.

The Milky Way in Autumn

The Milky Way passes through Cassiopeia, Perseus, and Cygnus (still in the west) during autumn evenings. While not as bright as the summer galactic center, this section is rich in star clusters and nebulae. Sweeping the Milky Way with binoculars through Cassiopeia and Perseus reveals numerous clusters and dark nebulae.

Planets in Autumn

Autumn morning skies from northern latitudes are the best time to catch Mercury before dawn. Jupiter and Saturn oppositions that fall in autumn provide all-night visibility during comfortable (if cool) evenings.

Meteor Showers

The Orionid meteor shower peaks in late October, producing about 20 fast meteors per hour from debris shed by Halley's Comet. The Leonids in November can occasionally produce spectacular storms.

Autumn Observing Tips

• Dress for cooling temperatures. Autumn evenings can start mild but turn cold quickly after sunset.
• Take advantage of longer nights. After daylight saving time ends (in areas that observe it), darkness arrives early, giving more evening observing time.
• Look for the zodiacal light. In autumn, a faint cone of light may be visible along the ecliptic in the east before dawn, caused by sunlight reflecting off interplanetary dust.
• Hunt for Andromeda. Make finding M31 a priority. It is a rite of passage for every stargazer.

Explore the Autumn Sky

Open StarGlobe to identify autumn constellations and locate the Andromeda Galaxy from your location. The autumn sky may lack summer's drama, but it offers its own quiet beauty -- vast, dark skies framing the farthest objects visible to the naked eye. See also our winter, spring, and summer sky guides.