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Last Week's Stargazing Tips

September 23: Last-Quarter Moon

The Moon reaches last quarter today. Half of the side that faces Earth is bathed in sunlight, while the other half is in darkness. When the Moon is at last quarter it is leading Earth in our planet’s orbit around the Sun.

September 22: Autumn Skies

The Sun changes hemispheres today. It crosses the equator from north to south, a moment known as the equinox. That ushers in autumn here in the northern hemisphere, and spring in the south.

September 21: Mu Cephei

The reddest star in northern skies stands high overhead during the evening hours. Its official designation is Mu Cephei, but it is also known as the Garnet Star. It is a red supergiant, which means it is much larger and cooler than the Sun.

September 20: Moon and Aldebaran

Aldebaran, the bright orange eye of Taurus, the bull, rises to the lower left of the Moon before midnight, and stands closer to the Moon at first light tomorrow.

September 19: Vela X-1

Enif, the star at the nose of Pegasus, the flying horse, is in the east at nightfall, to the upper right of the Great Square of Pegasus. The star is about 670 light-years away, so the light we see from it tonight actually left the star in the 1340s.

September 18: Autumn Constellations

As summer comes to an end, the constellations of autumn are moving into prime-time evening viewing hours. The best known are from Greek mythology: Pegasus, Andromeda, Perseus, Cassiopeia, and Cepheus, all of which stand high overhead in mid-evening.

September 17: The Colt

Equuleus, the colt, graces the evening sky this month. The tiny constellation looks like a flat-topped pyramid. A couple of hours after sunset, it stands about halfway between the eastern horizon and the point directly overhead.