As the nights lengthen, Rod Mollise reveals rewarding objects to seek out in suburban and city skies this autumn
PART 3 OF 4
Autumn’s arrival means the evenings are drawing in and the promise of long, dark, starry nights beckons us to get our telescopes out. As summer’s jewels recede and the delights of winter make their first appearance, we are presented with a view away from the plane of the Milky Way. Galaxies are again the main attraction for observers and there are some great ones lurking in autumn skies. Autumn also offers a good selection of other objects, from star clusters to nebulae too.
The key to exploring the urban night sky is to ensure you have the tools: larger apertures will reveal more. But perseverance is also important – you will be amazed at the marvels you can discover. Let’s get stuck in!
Autumn sights
Take our tour of autumn’s favourable constellations, unearthing jewels as we go
Pegasus, the Flying Horse
This well-known constellation is easy to find in the night sky
Pegasus’s Great Square – three bright stars in Pegasus, one in Andromeda – is easy to spot. Extending from the Square’s southwest corner is a line of stars that represents the Horse’s neck and head, terminating in brilliant mag. +2.3 Enif (Epsilon (ε) Pegasi), Pegasus’s nose. Just 4˚ northwest of this is target number one, globular star cluster M15 (mag. +6.3, 18’ across). Although it’s easy to see, resolving its stars is difficult for smaller instruments. In the city, what is visible depends on your telescope’s aperture: the larger the better. The most impressive thing about M15 is its bright core. Most groups of galaxies in Pegasus are faint, but spiral galaxy NGC 7331 (mag. +9.48, 10’10” x 3’42”) can be seen by urban astronomers.
Andromeda, the Maiden
The famous constellation is at the northeast corner of the Great Square
M31 (mag. +3.4, 3°9’ x 1°1’) is so bright it can be seen with the naked eye, even in the city. Located 7˚30’ northwest of mag. +2.0 star Mirach (Beta (β) Andromedae), M31 is so large you’ll need binoculars or the widest field telescope. In the suburbs, it’s possible to glimpse its spiral structure. A 12-inch or larger reflector reveals a bright star cloud near its southwestern tip: NGC 206, an oval, 3’-long brightening of the galaxy’s nebulosity. In suburban skies, 8-to 12-inch telescopes reveal one of M31’s many globular star clusters, mag. +13.8 G1, also known as Mayall 1.
Like the Milky Way, M31 has a number of smaller galaxies orbiting it. The brightest, M32 (mag. +8.0, 8’30” x 6’30”), lies 24’ south of its big sibling. It’s easy to see in 3-inch refractors in the city and in 50mm binoculars from darker sites.
M31’s other bright companion, M110 (mag. +8.0, 21’54” x 11’), is difficult to see with reflectors of 4-inch aperture, but easier to view with a 6-inch.
Finally, the outstanding planetary nebula NGC 7662 (mag. +8.3, 20” x 15”) is easy to see from the city, even in 3-inch refractors, if you use 200–300x magnification.
Triangulum, the Triangle
A small constellation that’s home to one of the gems of the night sky
While its stick figure – a triangle of 3rd and 4th magnitude stars – doesn’t stand out, Triangulum should be visible in most urban skies if you know where to look and you’ve allowed it to climb high in the sky. That’s more than can be said for the much larger constellation it lies next to, Pisces, the Fishes. An attractive constellation from darker skies, Pisces’s member stars are mostly faint, near mag. +5.0, and thus the Fishes suffers in city skies and may be completely invisible. The deep-sky objects it does contain are equally faint and difficult to realise from the city and suburbs.
Triangulum, however, contains one of the most beautiful galaxies in the sky, M33 (mag. +5.7, 68’42” x 41’36”), the Triangulum Galaxy, with wide-open spiral arms and a near face-on orientation. But it is difficult to see in the city and any moisture in the air will make viewing the spiral arms almost impossible. A UHC-type nebula filter can help and may even reveal a small bright patch on the northeastern edge of the spiral, M33’s titanic nebula NGC 604.
Cassiopeia, the Queen
This W-shaped constellation holds two Messier clusters
First up is an interesting cluster, NGC 457 (mag. +6.4, 20’ across). Once you have it in the eyepiece, you’ll understand how it got its nickname, the ET Cluster. This medium-sized group of stars forms a little stick figure with an upraised arm that seems to be waving across the lightyears. The googly eyes, one of which is mag. +4.95 star Phi (φ) Cassiopeiae, do suggest a comical extraterrestrial. There is a red star in ET’s right armpit that makes the cluster look even more attractive.
M103 (mag. +7.4, 6’ across) has 40 stars, but expect to see up to 15 from light polluted areas, depending on aperture. Luckily, M103’s few suns, which form an equilateral triangle, are scattered across a small area, so it looks rich in the eyepiece. M103 is better from urban rather than dark sites, as out of the city the cluster melts into the star-rich background. M52 (mag. +6.9, 16’ across), west of Cassiopeia’s ‘W’, is far better, showing as a larger, brighter and richer circle of at least 20 stars with a 3-to 4-inch refractor.
Cepheus, the King
Northwest of Cassiopeia lies her husband
The emission nebulae of Cepheus are a challenge for urban observers, but there is one good planetary nebula in the constellation: NGC 40 (mag. +10.9, 37” across), the Bowtie Nebula. It’s formed by two arcs of material opposite each other around the mag. +11.6 central star, which form the tie’s knot. The Bowtie’s magnitude sounds forbidding, but that is not a problem as it is small but bright.
Perseus, the Hero
Riding high in the east and full of treasures
This constellation, which represents the hero of the Andromeda myth, is not only distinctive in urban skies, being blessed with numerous bright stars, it holds one of the most beautiful deep-sky objects in the sky.
Perseus’s treasure is actually two objects, bright open star clusters NGC 869 (mag. +3.8, 30’ across) and NGC 884 (mag. +3.8, 30’ across). Bold in a small telescope, they sit just 25’ apart. This is the famous Double Cluster. NGC 869 shows 30 stars to a 2-inch refractor under most conditions, while NGC 884 looks slightly less rich and is also more noticeably elongated.
M76 (mag. +10.1, 3’7” x 2’3”), the Little Dumbbell Nebula, isn’t bright but it’s not large either, so its light is concentrated. It actually looks more like a dumbbell than its more famous relative, M27, the Dumbbell Nebula. With increased aperture, say a 12-inch reflector, M76 gives up more nebulosity and begins to resemble a rectangle rather than two round spots. On the best nights, arcs of nebulosity connecting the two lobes become visible.
While the north of Perseus is a place of open clusters, the southern half is littered with galaxies. Most are beyond the range of urban astronomers with small telescopes, except for one: lenticular galaxy NGC 1023 (mag. +10.2, 4’46” x 2’11”) shines through heavy light pollution and is visible with a 4-inch refractor.
Aquarius, the Water Bearer
A trickier constellation with some challenging wonders to uncover
M2 (mag. +6.3, 16’ across) rivals the best globular star clusters of autumn. In the city, it takes reflectors of 10-inch aperture to resolve the many stars ringing the bright core, but even a 4-inch version provides tantalising views. NGC 7009 (mag. +8.0, 41” x 34”), the Saturn Nebula, was given its nickname by its discoverer Sir William Herschel in the 18th century. With enough aperture and magnification, it does look a little like Saturn when its rings are edge-on. NGC 7293 (mag. +7.6, 25’ across), the Helix Nebula, is a great ring of nebulosity that is worth viewing. An OIII filter shows the nebula’s dark centre and averted vision reveals mottling in the ring and hints of the streamers that give the Helix its name.
Cetus, the Whale
A sprawling constellation where you’ll find an impressive spiral galaxy
Cetus lies close to the horizon, although the area that contains M77 (mag. +8.8, 7’ across) is slightly higher. M77 is a Seyfert galaxy, meaning it has a very bright core due to a massive black hole at its centre. In a 3- or 4-inch reflector, it shows a small, bright central region when using 100x magnification and upwards.
Capricornus, the Sea Goat
The sail-shaped constellation can be hard to see
The Sea Goat is often masked by smoke and haze near the horizon – the constellation never gets much higher than 25°. But it contains M30 (mag. +7.7, 12’ across) which is easy to see with a 6-inch or larger refractor from badly lightpolluted areas. From the suburbs, with a 12-inch refractor and 150x magnification, two streams of stars extend from the cluster, looking like the horns of a goat.
Taurus, the Bull
One of the most beautiful constellations in the night sky
The V-shaped pattern of the face of the Bull is formed from the brightest stars of an open cluster, the Hyades (mag. +0.5, 5°30’). It is so large because it is so close to Earth – only 151 lightyears away. The size of the group means it’s best suited to small, short focal length telescopes and binoculars.
M1 (mag. +8.4, 4’ across), the Crab Nebula, was the first object to make it on to Charles Messier’s list. While it is easy to find, only 1° northwest of star Beta (β) Tauri, which forms one of the corners of Auriga’s pentagon, it is badly compromised by light pollution.
You don’t need a telescope or a Go-To system to locate M45 (mag. +1.2, 2°), the justly famous Pleiades – it is a brilliant open cluster. It can be mistaken for Ursa Minor’s Little Dipper asterism; its brightest stars are arranged in a similar, vaguely dipper-like shape.
The rise of M45, the Pleiades, heralds the end of autumn and the advent of winter, and brings this part of our seasonal tour to a close.
‘Uncle’ Rod Mollise is an American amateur astronomer and writer who lives near Mobile, Alabama. He is the author of Choosing and Using a New CAT