As we explained last week, this evening is likely your last chance to ever see Venus pass in front of the sun—unless you plan on surviving until the year 2117. The transit of Venus, as it’s called, happens in pairs spaced eight years apart, separated by gaps of more than a century. Follow these steps to see this twice-in-a-lifetime astronomical phenomenon.
1. Be ready at the right time: Fortunately, astronomers are able to predict precisely when the transit will begin and end, so you shouldn’t be caught off guard. Viewers in North America will be able to see roughly the first third of Venus’ journey across the face of the sun, beginning in the evening and ending when the sun sets. In the United States, it will begin at 6:04 Eastern, 5:04 Central, 4:05 Mountain and 3:06 Pacific Time. For those in parts of Asia and Africa, the transit will be in progress when the sun rises tomorrow, on June 6th. Lucky residents of East Asia and the Pacific will be able to see the entire event, which takes about 6 hours and 40 minutes.
2. Know what to look for: The transit is essentially an eclipse, but because Venus is so much farther away than the moon, it appears as a tiny black dot roughly 1/32 the diameter of the sun, instead of blocking out a large portion of it. The planet will make its first contact against the upper edge of the sun at the times listed, and will gradually make its way inward until it is fully inside about 17 minutes later. The planet will then move diagonally across the sun, moving downward and to the right, until it exits from the bottom-right edge, ending the transit.
3. Take the proper precautions: As with solar eclipses—or anytime, really—it’s not safe to look directly at the sun, either with the naked eye or through a digital camera, but there are several other options. Many observatories are holding public viewings of the transit through telescopes outfitted with special filters. You can also purchase an inexpensive pair of solar eclipse viewing glasses, which block out all but 0.003 percent of visible sunlight, at observatories, planetariums and museums, or use a piece of #14 welder’s glass if you happen to have some on hand. Don’t try to use normal sunglasses, as they don’t block out enough near-infrared radiation to prevent harm to your eyes.
There are simpler options, too. You can make a box pinhole viewer in just a few minutes with commonly available materials, or make an even simpler viewer by taking a piece of cardboard, punching a hole in it, and holding it up to the sun’s light. An image of the transit will be projected on the ground beneath the cardboard, showing a miniature version of Venus moving across the sun. The farther away you hold the viewer from the project surface, the larger the sun and Venus will appear. Telescopes and binoculars can also be used to project an image of the transit if you turn the large end toward the sun and point the smaller end toward the ground. Make sure never to look directly into the eyepiece itself, only the projection.
4. Take a picture: Since you won’t see this ever again, capturing it for posterity is a great idea. If you want to photograph the transit, you can use the same eclipse viewing glasses or filters over your camera’s lens, but make sure not to use the lens uncovered—the sun’s powerful rays will fry your camera just as they’ll damage your retinas.
5. Hope for the best: Weather, of course, will play a role in determining whether you get to enjoy this rare astronomical event—if it’s cloudy where you live, you’re basically out of luck. However, NASA will broadcast streaming coverage from 10 observatories around the world, so you can enjoy the transit virtually even if weather doesn’t cooperate. Also, transit-themed events and festivals are being hosted at a number of sites around the country, rain or shine, including the National Mall, where the Air and Space Museum is holding curator talks, viewings of the transit through safe solar telescopes and projecting the event on large screens for everyone to see.