Autumn astronomy: the best targets for longer nights

As nights get longer, these are the top night-sky highlights of autumn and how to see them.

If you're a planetary imager, make sure your laptop and software are ready for a new season of astronomy. Credit: Steve Marsh

From September to December, the new astronomy season kicks off, and astronomers get the chance to view summer jewels, catch autumn gems at their finest and take the first glimpses of the delights of winter.

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Thanks to a quirk of Earth’s axial tilt, as we approach the autumn equinox in the northern hemisphere the ever-lengthening nights bring astronomical summer delights to view earlier in the evenings, set against darker skies.

The glories of the Milky Way stay on view, giving us a chance to spot nebulae, clusters and the star clouds for that little bit longer.

Milky Way delights

Early on in September we can still see the Milky Way stretching up across the sky, starting with the centre of our Galaxy almost due south at the end of twilight. For more on this, read our guide How to see the Milky Way.

Here we have gorgeous summer objects such as the Lagoon Nebula (M8), the Trifid Nebula (M20) and the Omega Nebula (M17), while star clouds and clusters such as M24 and the Wild Duck Cluster (M11) cry out to be viewed.

An image of the Lagoon Nebula captured by the VLT Survey Telescope at ESO’s Paranal Observatory, Chile. Credit: ESO/VPHAS+ team
An image of the Lagoon Nebula captured by the VLT Survey Telescope at ESO’s Paranal Observatory, Chile. Credit: ESO/VPHAS+ team

The Summer triangle

Higher up towards the zenith all three members of the Summer Triangle asterism – bright stars Deneb, Vega and Altair – remain on view well into December.

Bounded within this triangle is the stunning planetary nebulae the Dumbbell Nebula (M27) and the Ring Nebula (M57). If you enjoy double stars and multiple stars, Albireo in Cygnus should be on your observing list.

Its golden yellow and sky blue components are easily resolvable with a small telescope.

Dark nebulae

Engrossed in the splendours of our Galaxy, it is easy to overlook dark nebulae. Look along the Milky Way towards Cygnus and note the split in the Milky Way.

This is the Cygnus Rift; a huge cloud of interstellar dust obscuring our view of background stars. Cosmic dust like this lies in the plane of our Galaxy and so gives rise to many dark patches that are worth looking out for.

Globular clusters

If you can pry your gaze from our Galaxy, take a look at the multitudes of globular clusters that surround it in a halo. For us this extends from Scorpius up into Serpens, Ophiuchus, Hercules and down into Capricornus, Aquarius and Sagittarius.

These incredibly distant objects, several thousand lightyears away, include such gems as M13 and M92 in Hercules, M5 in Serpens, and M22 and M28 in Sagittarius.

Through small telescopes they often look like little cotton balls.

A view of M92, as seen by the Hubble Space Telescope. Credit: en:NASA, en:STScI, en:WikiSky - en:WikiSky's snapshot tool
A view of M92, as seen by the Hubble Space Telescope. Credit: en:NASA, en:STScI, en:WikiSky – en:WikiSky’s snapshot tool

Approaching the end of autumn

As we move into October and November, the constellations of Aquarius and Capricornus become better placed over in the south, rich with promising targets.

Pick off the final batch of globular clusters such as M30, M2 and M72, along with M15 up in Pegasus. Seek out the faint but large Helix Nebula and the Saturn Nebula, two planetary nebulae in Aquarius.

For more, read our observing guide 6 planetary nebulae to spot in the night sky.

Winter sights

From October until the end of the year the final glories of the autumn skies come into view, taking us into the more distant reaches of space.

Pegasus has the often overlooked galaxy NGC 7331, while close by lies the more challenging Stephan’s Quintet of galaxies. This is prime time for galaxies as Andromeda and Triangulum move into sight.

Pick a clear, transparent night, head to a dark sky area and let your eyes become properly dark adapted (it takes about 40 minutes) to stand the best chance of seeing their namesake galaxies, M31 and M33, the farthest objects it is possible to glimpse with the naked eye.

Finally, as we approach December, stunning Taurus and mighty Orion come into view for us to feast our eyes on, heralding the start of winter’s observing and the joys it promises.

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Paul Money is BBC Sky at Night Magazine’s Reviews Editor. For more of his stargazing advice, visit his website Astrospace.