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Comment by xrd | Hacker News Reader

I didn't read all the comments so perhaps this is already answered? I'm curious why this is the largest when you've got massive land areas in the Midwest where very few people live.

As an Oregonian I'm both proud and surprised. Nice work to all involved.

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The midwest can definitely get dark, but the "seeing" isn't as good as the oregon outback for a few reasons, 1) elevation, most of eastern oregon is above 1200m, steens mountain is almost 3000m. 2) climate, the midwest can be very humid and hazy, whereas the high desert is very arid and clear, 3) obscuration, eastern oregon is covered in mountain ranges with dry basins in between (hence "basin and range" name), and you only have to go over one range from any kind of town to have its light totally blocked.

This is terrific. Thanks so much.

Can you elaborate on why the elevation matters? I mean, a few thousand feet isn't going to make up the distance between the earth and the star providing the light. ;)

Less atmosphere (the closer to the ground, the denser the air), above the clouds means no difraction, etc. through water.

Dry near zero humidity desert locations also have spectactular night views.

a similar blocking effect happens in Joshua Tree. Very clear skies even though LA is not far away.

The Midwest is smoothly populated with regular towns and farms. If you look at darkskymap.com, the darkest areas in Midwest are darker but not the darkest. It is only leave Corn Belt that get dark spots. But taxes going to the western deserts to get really dark.

The organization that grants these titles, DarkSky International, bases them more on local policy towards light pollution rather than the absolute magnitude of darkness. It's more about whether the local municipality has committed to good lighting ordinances etc.

Indeed. For example, Cranborne Chase Dark Sky Reserve isn't that dark at all. At darkest, it's at about Bortle 4, which means that the Milky Way is visible, but not that impressive, and if you have reasonably youthful eyes you could probably walk around without carrying a light source on an overcast day.

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