Don't Look Into the Light!

Any source of light that is designed to help humans see is bad for astronomers. Even very small white light sources have a very bad affect human night vision. Remember, we are trying to see objects in space that can be millions of light years away.

In general, it takes about three minutes of darkness to realize a third of our night vision. To get another third takes about thirty minutes more. The last third develops slowly over the next three hours. But while it takes many hours to fully develop our night vision, it can vanish in a single flash of bright light. So, if you arrive at a star party three hours after dark and flash everyone with your headlights, you may be facing some very unhappy campers.

Flash cameras are even worse because they tend to be right next to the people and the telescopes. Imagine looking through the eyepiece of a telescope -- a device designed to collect and focus light -- and someone a few feet away hurls a blinding flash directly into your optic nerve. Once night-adapted, bright light has a number of unfortunate affects on human physiology.

When going to a star party, please keep in mind a few courtesies astronomers lavish on one another to preserve night vision:

	Please... No flash photography after dark.
	Arrive early -- before sundown.
	Do not bring a flashlight unless it is tinted red and not terribly bright.
	Do not drive towards a crowd of observers with your headlights on.
	Shield lighters, cell phones and other sources of white light.
	Do not leave your car doors open -- or manually turn off interior lighting.
	Resist the prey-animal urge to start a campfire.

If you have never been out in the dark with the express purpose of keeping it dark, some of this will probably seem a little obsessive. But the first time you do this, then squint in discomfort when someone opens their cell phone, you will understand.

Some things cannot be avoided. For instance, some modern cars won't let you turn off your headlights or interior lighting. Also, some people will arrive after dark and must be able to see to park. Just do what you can and be patient while your night vision develops.

Light pollution, in general, is a real problem. Many professional quality observatories have been rendered useless by America's need for 24-hour daylight.

Click here to learn more about the light pollution problem on a larger scale.