Light pollution and observatories

Before going stargazing it is useful to check a good place where there's no light pollution or other distractions. Then where are those areas and what does light pollution mean?

What is light pollution?

Light pollution is misdirected or unwanted artificial illumination. It is usual in most of the inhabited areas around the world. Some researchers say that up to 99% of United states and European people live under light-polluted skies. The cause behind light pollution, or in other words photopollution or luminous pollution, is bright lights, especially blue lights, which are kept on for 24 hours per day. Blue light reflects differently in air than red light, which allows more light to get lost to the sky.

A good example of unnecessary lighting is parking lots and big commercial walls on which the lights are kept on all the time. These days light planning for cities has luckily developed in a better direction. For example lights are syncronised to react to how much traffic there is and at nighttime lights dim until pedestrians come which is when the lights get brighter.

Light pollution can cause for example a red-looking horizon at night which complicates stargazing by hiding the Milky Way and most of the stars.

What can we do?

First of all we can turn lights off when not needed, especially during nighttime. If possible use led-lights where the light intensity can be adjusted. When planning house lights it's good to know how different lamps direct the light. From the picture you can see more clearly how different light fixtures spread the light around. Outdoors it is good to have automatic lights which react to movement and turn on only then. Tips for good lightning:

• The light is only as bright as needed
• The light is directed correctly only to the targeted areas
• The spectrum has a longer, red wavelength
• The light is only where needed.

Where to go?

Here are a couple of tips for you to find a good spot to explore the sky as it is meant to be seen. On this page is a map of the light pollution in different areas. Check the map for the darkest place possible. The map also shows nearest observatories if you are interested to visit. As you can see not even the observatories are always in good locations in terms of light pollution. A good example of that is Observatorio Kaivopuisto in Helsinki.

Normally a good place for stargazing is where there are no city lights around nor other obstacles, for example a tall forest or big buildings. Recommended time to go on a stargazing adventure is near new moon when you can avoid most of the moonlight. In terms of seasons the fall and the spring are the most opportune time to see the sky at its full potential.