Constellations Visible Despite Light Pollution: A Stargazer's Guide

Light pollution can make it difficult to see the stars, but it is still possible to spot some constellations from light-polluted cities. The brightest few hundred stars are resistant to light pollution, meaning the outlines of most constellations are accessible in suburban skies. Constellations that can be seen from light-polluted areas include Orion, the Plough, and Pegasus. In the summer and autumn months, Albireo (Beta (β) Cygni) in Cygnus, and Epsilon (ε) Lyrae in Lyra, are also within reach of a 150–200mm aperture telescope.

Constellations that are visible through light pollution include Orion and the Plough

You can tell the time using the position of the pointer stars in the Plough, as if the whole constellation were a giant clock with the pole star at the centre. Orion is also simple enough to spot when looking for his belt – three bright stars in a line. Looking below the belt reveals three much fainter stars forming the sword. The object at the middle of this is not a star, but the Orion Nebula – a cosmic nursery of new stars.

In the summer and autumn months, notable examples such as Albireo (Beta (β) Cygni) in Cygnus, and Epsilon (ε) Lyrae in Lyra, are comfortably within reach of a 150–200mm aperture telescope from sites with fairly bright night skies. If you’re interested in long-term observing projects with a telescope, you’ll also find that some variable stars – stars whose brightness fluctuates – like Algol (Beta (β) Persei) in Perseus, often periodically glow strongly enough to be seen through moderate light pollution.

To get the best results, you should perform the count close to the New Moon, and preferably near the autumn or fall equinox in September, when the constellation Pegasus sits high overhead around local midnight.

The brightest few hundred stars are resistant to light pollution, making the outlines of most constellations accessible in suburban skies

The brightest few hundred stars are resistant to light pollution, meaning that the outlines of most constellations can be seen from suburban areas. The Milky Way and Zodiacal Light are among the first to disappear in light-polluted skies, but the brightest stars and planets can be seen without trouble from the city centre. Constellations that can be seen from light-polluted areas include Orion and the Plough. You can even tell the time using the position of the pointer stars in the Plough, as if the whole constellation were a giant clock with the pole star at the centre.

Looking for Orion's belt – three bright stars in a line – is a simple way to spot the constellation. Below the belt are three much fainter stars forming a sword, and in the middle of these is the Orion Nebula, a nursery of new stars.

In the summer and autumn months, you can see some of the brighter double and multiple-star systems, such as Albireo (Beta (β) Cygni) in Cygnus, and Epsilon (ε) Lyrae in Lyra, with a 150–200mm aperture telescope from sites with fairly bright night skies. Some variable stars, such as Algol (Beta (β) Persei) in Perseus, periodically glow strongly enough to be seen through moderate light pollution.

The naked-eye planets are typically brighter than constellations and can be seen without trouble from the brightest city centres

The constellations that can be seen through light pollution are those made up of the brightest few hundred stars, as these stars are also resistant to light pollution. The outlines of most constellations can be seen in suburban skies, but fainter constellations are more challenging to make out.

The naked-eye planets are close enough to the Earth to form a disk in the night sky, and they shine with a more steady light than the stars. The brightness of a planet to the naked eye depends on its distance from the Earth, its apparent size, and the relative positions of the planet and the Earth in their orbits. For example, Mercury becomes brighter throughout November as it makes its way around the sun, and your best chance of seeing it is an hour prior to dawn or after sunset. Venus is so bright that it is often lost to the glare of the sun, but it can be viewed most of the year. Mars is another planet that can be seen with the naked eye. It gives off a notable red colouring and is highest in the sky around midnight, making it easier to spot.

If you're looking for constellations to spot through light pollution, Orion and the Plough are attainable targets. You can also try to spot the pointer stars in the Plough, as they can be used to tell the time.

The limiting magnitude of your stargazing site gives a numerical indication of whether a star or object can be seen there

The brightest few hundred stars are resistant to light pollution, making the outlines of most constellations accessible in suburban skies, although fainter constellations are more challenging. Constellations that can be seen through light pollution include Orion, the Plough, and Cygnus. The naked-eye planets are typically brighter still and can be seen without trouble from the brightest city centre.

To improve your chances of seeing stars through light pollution, it is recommended to get as high up as possible to reduce the impact of light on your line of sight. You can also use a small to medium aperture telescope to see some interesting targets. In the summer and autumn months, notable examples such as Albireo (Beta (β) Cygni) in Cygnus, and Epsilon (ε) Lyrae in Lyra, are comfortably within reach of a 150–200mm aperture telescope from sites with fairly bright night skies.

Brighter double and multiple-star systems can be seen through light pollution in built-up areas

Although light pollution makes it difficult to see the night sky, the brightest few hundred stars are resistant to light pollution, meaning that the outlines of most constellations are still visible in suburban skies. In built-up areas, you can see some of the brighter double and multiple-star systems, where two or more stars either appear close together or are whirling together as a gravitationally-bound group through space. Examples include Albireo (Beta (β) Cygni) in Cygnus, and Epsilon (ε) Lyrae in Lyra, which can be seen with a 150-200mm aperture telescope.

Some variable stars, whose brightness fluctuates, can also be seen through moderate light pollution. These include Algol (Beta (β) Persei) in Perseus, which periodically glows strongly enough to be seen.

The limiting magnitude of your stargazing site will give you an indication of whether a given star or object can be seen there. In the very brightest urban skies, the limiting magnitude is restricted to stars brighter than +4. The ideal limit of +6.5 is much better. From a dark rural site, you can see stars at least ten times fainter than the faintest visible in the city centre.

To reduce the impact of light pollution, it's best to get as high up as possible, for example, on the top of buildings. You can also check a dark sky calendar to pick the best night for stargazing.

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