The Two-Way
8:00 am
Mon June 4, 2012

As Venus Transits The Face Of The Sun, Here's How To Safely Watch

Originally published on Mon June 4, 2012 11:53 am

DO NOT STARE AT THE SUN.

Is that clear enough?

As we looked this morning for good guides about how to safely watch on Tuesday as Venus passes across the face of the sun, there was no escaping the stern warnings about what NOT to do.

In fact, NASA's first "observing tip" is "do not stare at the sun." After all, you could go blind. (If that link isn't working, and at 2:40 p.m. ET it appeared to be broken, see NASA's "safe solar viewing" package.)

Webcast Note (added at 2:40 p.m. ET): NASA plans to webcast a view of the transit here.

Consider yourself properly cautioned.

So, how do you safely watch as Venus — looking like a little black dot — starts across the sun at 6:09 p.m. ET on Tuesday in the U.S. and Canada?

NASA says welding goggles with No. 14 glass are "a good choice." And that "No. 14" is very important — it's the darkest shade they come in.

But most of us probably don't have time to run around and find welder's supplies. And it may be too late to find the cardboard "eclipse glasses" that always go on sale when there's a sun-related show.

That means your best bet may be the trusty "pinhole camera" like the ones you made in elementary school. Don't remember how to make one? Life's Little Mysteries has a how-to video.

Or, find your local astronomy club and see what safe viewing options its members have set up.

As for why you might want to watch, as The Associated Press says, "it's a spectacle that won't repeat for another century." So you're probably not going to be around next time, in 2117.

Also, the transit has played a key role in understanding some important things about our planetary neighbors. As NASA writes:

"Transits of Venus first gained worldwide attention in the 18th century. In those days, the size of the solar system was one of the biggest mysteries of science. The relative spacing of planets was known, but not their absolute distances. How many miles would you have to travel to reach another world? The answer was as mysterious then as the nature of dark energy is now.

"Venus was the key, according to astronomer Edmund Halley. He realized that by observing transits from widely-spaced locations on Earth it should be possible to triangulate the distance to Venus using the principles of parallax.

"The idea galvanized scientists who set off on expeditions around the world to view a pair of transits in the 1760s. The great explorer James Cook himself was dispatched to observe one from Tahiti, a place as alien to 18th-century Europeans as the Moon or Mars might seem to us now. Some historians have called the international effort the 'the Apollo program of the 18th century.' "

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.