Guide

Right outsideSky

The Summer Triangle in the autumn evening sky

September to November

The Summer Triangle is a big triangle of three bright stars, Vega, Deneb, and Altair, that ruled the summer sky. On autumn evenings it is still up after dark, high in the south and overhead in September and October, then sliding into the western sky by November.

Why this time of year

Summer's brightest star pattern has not gone yet. In autumn it stays in the early-evening sky, and it reaches the same spot about four minutes earlier each night, so at the same clock time it sits a little farther west each week.

How to notice it

  1. Go out after dark, by mid-evening in September or early evening in October and November, and find the darkest spot you can, away from porch lights and streetlights. Give your eyes a few minutes to adjust.
  2. In September and October, face south and tip your head far back: the three brightest stars high in that part of the sky are the triangle.
  3. In November, face west instead: the triangle hangs high in the western sky.
  4. In November, look again an hour later. The whole triangle will have slid farther west, closer to the horizon.

Try this with kids: Which corner of the triangle looks the bluest to you?

Word to know: An “asterism” is a star pattern that is not itself an official constellation, so the triangle is made from three different constellations' stars.

Safety

  • Bring a jacket and a blanket for lying back on cool autumn nights, and stay in a safe, familiar spot if going out in the dark.

Sources

  • earthsky.orgEarthSky, dated 2015-09-01: 'This huge star pattern looms from south to overhead at mid-evening in September and early evening in October.' Vega is sapphire-blue; Deneb tops the Northern Cross; Altair has a fainter star on either side.
  • earthsky.orgEarthSky, dated 2025-11-16: 'Look for the Summer Triangle after dark in early November', 'high in your western sky', and 'As evening deepens, the Summer Triangle descends westward'. Also: it returns to the same place 'some four minutes earlier with each passing day, or two hours earlier with each passing month.'

Checked against these sources on September 29, 2026.

In the guide for September, October, November

Also worth noticing