Date: October 24, 2009

Title: Great Light Switch Out


Podcaster: International Dark Sky Association

Organization: International Dark-Sky Association

Description: The Great Light Switch Out is a program to encourage people to make their outdoor light fixtures dark sky friendly.

Bio: Established in 1988, the International Dark-Sky Association is an educational, environmental 501(c)(3) nonprofit dedicated to protecting and preserving the nighttime environment and our heritage of dark skies through quality outdoor lighting. With thousands of members in more than 70 countries, IDA is the leading authority concerning the problems and solutions related to light pollution.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Jeff Dutton, member observing chair of the Durham Region Astronomical Association. The DRAA is a standing organizational member of the International Dark-Sky Association, committed to abating light pollution. Pay us a visit at


P1: Look at all this candy, I sure do love trick or treating!

P2: We’ve only got one house left, that really bright one at the end of the street.

P1: You mean the one we’ve been staring at all night? It’s been lighting up the entire block!

P2: That’s the one! Last year it blinded Mrs. Kravitz, and she thought our fairy princess costumes were ghosts, so she didn’t give us any candy.

P1: Why do think it’s so bright?

P2: Probably for safety…

P1: WHOSE safety? The light makes a big shadow when it hits the shrubs. It’s totally dark on our side, and if you’re walking down the porch steps you can’t see where you’re going!

P2: You remember how last year, your big brother Matt hid in the shadow and scared us coming down those steps?

P1: I sure do! We couldn’t see him at all until he jumped out at us!

P2: Hey, we learned about this in Astronomy class last week. A guest speaker from the International Dark-Sky Association talked about how people like to over light their houses for safety, but how in reality the excess light is just creating blind spots and glare—and destroying the view of the stars.

P1: Well it sure kills the atmosphere on this street! I feel like it’s daytime. I would hate to be their neighbor, with the light shining in the window all night. I don’t think I could sleep. Did the speaker from the International Dark-Sky Association say how to fix the problem?

P2: They said there’s really simple solution. It’s all about using light where you need it, when you need it, and for how long you need it. They talked about pointing the light downwards, on the ground, and shielding the bulb, so you don’t waste energy shining the light up.

P1: So if the light was shining down with a shield over it, that means we wouldn’t see the light bulb, and there wouldn’t be all that glare. So we could have seen Matt hiding in the shadows.

P2: Exactly! Dark sky doesn’t mean dark ground!

P1: It sounds like that’s common sense. But if there are so many benefits, how come more people don’t do it?

P2: Most people don’t consider the effects of their light, they think brighter means safer… what they don’t know is that the less light you use, the less you actually need to see. The speaker was talking about how our eyes adapt to the night, but that it takes twenty minutes to become fully dark adapted, and when you are distracted by something bright, it makes it more difficult to see.

P1: So you’re telling me we could actually see better if they put in a different fixture?

P2: Right, if the light were evenly spaced and didn’t glare.

P1: Where can we find fixtures like that?

P2: You can usually find fixtures at your local hardware store. You just have to look for one that’s designated dark sky friendly, or fully shielded.

P1: What’s fully shielded?

P2: It means the light doesn’t shine up, above 90 degrees, so you can’t see the actual light source. The bulb is completely hidden.

P1: Wouldn’t that actually make the light less efficient?

P2: No because you’ve got the light concentrated on the ground where you need it. People can lower the wattage and their energy use. The speaker also said that for the International Year of Astronomy there’s a program called the Great Light Switch Out to encourage people to make their fixtures dark sky friendly, and good neighbor friendly.

P1: The Great Light Switch Out…Sounds like a great program, let’s go tell this house about it.

Doorbell Rings

Just in time for daylight savings, the International Dark-Sky Association encourages you switch your porch light to one that’s dark sky and good neighbor friendly. IDA has a comprehensive database of practical guides and brochures to help in the education process. The newly released PG 3 – Residential Lighting: a Good Neighbors Guide, will give you all the information you need to observe the stars while helping you see better at night. Visit for information on how you can be part of the Great Light Switch Out!

End of podcast:

365 Days of Astronomy
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