Light Pollution.  What causes it and is there a low cost way to get around it?

Anyone who’s looked at the night sky in the city or suburbs knows what light pollution is. The light from street lights, cars, shopping centres, homes and countless other sources scatters in the atmosphere turning the night sky into a dull, murky mush and blocking the light from all but the brightest stars and planets.

Light pollution is a costly and wasteful use of resources. Through billions of years of evolution, the natural cycle of day and night is tightly embedded into the DNA plants and animals. By disrupting this cycle via artificial lighting, not only the environment is harmed but our own health and wellbeing is adversely impacted as well. 

On top of the cost and harm it causes, light pollution robs everyone of a good chunk of the wonders of a truly dark night sky. 

We often get asked at BINTEL if there’s a way to get around light pollution when observing through a telescope or taking astro images. 

Sadly, there’s nothing that can be done to stop it completely except getting away from city lights. 

BUT there’s a number of light pollution reduction (LRP) filters and accessories that can assist somewhat. 

These work by blocking the light frequencies from some of the main sources of light pollution while allowing through the narrow band of light produced by astronomical objects like nebulae. They are a start and will let you see more when observing from washed out skies in the city or suburbs. 

One product we’ve been impressed by is the Orion Sky-Glow filter. This $115 gizmo screws into the bottom of any standard 1.25” eyepiece that comes with almost every telescope.

The light we see from above us comes from two main sources. One is of course direct starlight from the stars themselves. You might notice that stars have slightly different colours and this difference becomes more obvious viewed through a telescope. The light from the Moon, planets and some types of nebula comes to us in the same way everything in daylight is seen. Light from the Sun (or their nearest star) reflects off it. Galaxies including our Milky Way are lit up by the light from stars as well. 

Even though we see stars as different colours, they emit light across a very wide range of frequencies. 

A large percentage of light pollution that blocks out the night sky comes from street lighting that does not emit light across all visible light frequencies. A filter like the Orion Sky-Glow can block out a significant percentage of this polluting light. This will increase the contrast and details of astro objects that shine through reflected star light. 

Orion SkyGlow Filter

(Photo of M42 showing the effects of a SkyGlow filter)

One spectacular type of astronomical object that’s always a favourite with telescope owners are emission nebulae like the Orion Nebula (M 42) or the Eta Carina (The Keyhole) Nebula and Tarantula Nebula in the far southern skies.  These types of nebulae don’t directly reflect starlight. Instead, the gasses they’re made of them absorbs energy from nearby stars and emits light at a different and very limited range of wavelengths.  Filters can block out light pollution but only have to let a very limited range of light through to bring out much of the details of these types of nebulae and greatly improve the viewing and imaging of them in city and suburban skies. 

Bottom line – will I see a difference using a light filter like the Orion Sky Glow?

The short answer is that there is a very good chance it will reduce the impact of light pollution and will improve your views. Planets and star clusters will improve slightly. Objects like the Orion Nebula will definitely be improved. 

Nothing beats a trip away into the country to spend some time under Australia’s magnificent dark night sky, but the Orion Sky Glow Filter is a low cost accessory and one we suggest is well worth trying.  

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