Friday, December 2, 2011

Cities from Space - San Diego, CA

It is day two of the Visible Suns Cities from Space Advent celebration.

Today the view is of San Diego, California USA and Tijuana, Mexico:

Image from NASA's The Gateway to Astronaut Photography of Earth

You can easily see the international border between San Diego and Tijuana. It is marked by an orange line of light - the light of low-pressure sodium lamps (LPS). As you look northward from the border you can see a variety of colors in the city lights. Notice that north of San Diego the lights are predominantly the orange of LPS. LPS lighting is the least damaging to astronomy and these lights are there because lighting ordinances were put into place in the 1980s to protect Palomar Observatory.

The image was taken November 30, 2010 by the Expedition 26 crew of the International Space Station.

I'll have another city from space tomorrow as this Advent celebration continues.  Another way to celebrate Advent is to head over to the Pepsi Refresh and vote for the astronomy project being put forward by the International Dark-Sky Association. Your daily vote can help to make the project to happen.

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