Venus transit: A last-minute guide

See the article for pictures and maps
I live in Atlanta, and it's been cloudy all day, so we'll probably not be able to see it live unless it clears up quickly.

http://cosmiclog.msnbc.msn.com/_news/2012/06/05/12056397-venus-transit-a-last-minute-guide?lite

By Alan Boyle 6/5/2012

Thousands of scientists and skywatchers around the world have made detailed plans to monitor today's transit of Venus across the sun, but chances are that word of the last-in-a-lifetime event is just now sinking in for millions of just plain folks — so what's the big deal? And what's the best way to watch the transit?

We've had dozens of stories about Venus' day in the sun over the past few weeks, but for those of you who are just tuning in, here are the top 10 things to keep in mind about today's transit, whether your skies are sunny or completely socked in:

Venus comes between Earth and the sun five times in the course of every eight years, but because of the inclination of the planets' orbits, Venus usually misses passing over the sun's disk, as seen from Earth. In fact, that passing-over phenomenon occurs only twice in the typical person's lifetime. Two transits occur eight years apart, but each pair is separated by either 105.5 years or 121.5 years. We had a Venus transit in 2004, and we're having another one today. The next one won't come until 2117. So if you're into rare sky phenomena, today is as good as it gets.

Venus' disk begins to pass over the left edge of the sun's disk a little after 6 p.m. ET, and makes a stately crossing that lasts until about 12:50 a.m. ET. (Of course, the sun will have set on the East Coast by then.) Some part of the transit will be visible from most locations on Earth — though you're out of luck if you're in eastern South America, western Africa, the Iberian Peninsula, Antarctica or the middle of the Atlantic.

The precise time when different edges of the planet's disk cross the sun's edge is actually a big deal. Those times vary by location on Earth, and the variations can be used to calculate dimensions and distances in the solar system. Today, so much is known about those dimensions that astronomers can predict the key times of the transit based on your location. To find out what you can see when, use the U.S. Naval Observatory's transit computer.

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This is where I type out the bold-face warning that you should never gaze at the sun without proper eye protection. Sunglasses are not adequate. Neither are black plastic garbage bags, or film negatives. Unsafe viewing can damage your retinas. This video from "Astronomy Dave" Fuller explains the difference between proper and improper eye protection, not only for the transit, but for anytime you want to observe the sun:

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I'm guessing that most transit-watchers will be getting at least some of their looks via the Internet, particularly if the weather is lousy. Here's a listing of the webcasts that'll be available, including msnbc.com's simulcast of NASA's coverage:

NASA TV and NASA EDGE at Mauna Kea: The Hawaii show starts at 5:45 p.m. ET, and you should be able to watch it here:

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There are a bunch of webcasts to choose from, so even if some are at locations that are cloudy, some should work.

The following is from the SLOOH space camera, so doesn't have to worry about clouds:

http://www.slooh.com/transit-of-venus/

http://events.slooh.com/

http://www.cnn.com/video/?/video/cvplive/cvpstream1&hpt=hp_c2#/video/cvplive/cvpstream1


The following has info about past, present, and future eclipses of various kinds:

http://eclipse.gsfc.nasa.gov/eclipse.html