Rare solar events predicted

May 18, 2012

Three visually distinctive solar events will occur during the next two weeks, with a rare partial solar eclipse visible Sunday evening. (San Francisco Chronicle)

A partial lunar eclipse will follow several days later, and then will come a rare visual of Venus crossing the face of the sun — an event called a “transit.”

The solar eclipse will start at about 5:16 p.m. and last about an hour, said astronomer Andrew Fraknoi of Foothill College and the Astronomical Society of the Pacific.

All eclipses, including these, can be dangerous to eyes if viewed without protection. Dark sunglasses are not adequate, Fraknoi warned.

More than 35 percent of the full moon’s light will be blocked June 4 when Earth shadow’s the moon’s face at around 3 a.m. And the following day, Venus does her thing, blocking a corner of the sun starting at about 3 p.m.

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From SPACE.COM’s website (and generally accepted safe viewing):

Safety first

Warning: Never look directly at the sun, either with the naked eye or through telescopes or binoculars without the proper filters. Doing so could result in permanent and serious eye damage, including blindness.

To safely observe the annular eclipse, you can buy special solar filters to fit over your equipment, or No. 14 welder’s glass to wear over your eyes. No. 14 is denser than the standard No. 12 available in hardware stores and can be purchased only at specialized welders’ supply stores.

You can also buy “solar shades,” special glasses widely available from telescope stores before eclipses. Do NOT use standard sunglasses or any kind of homemade sun-shading contraption.

The safest and simplest technique is perhaps to watch the eclipse indirectly with the solar projection method. Use your telescope, or one side of your binoculars, to project a magnified image of the sun’s disk onto a shaded white piece of cardboard.

The image on the cardboard will be safe to view and photograph. But make sure to cover the telescope’s finder scope or the unused half of the binoculars, and don’t let anybody look through them.

If you do get the proper filter, you can take some impressive photos of the eclipse with almost any camera through your telescope or binoculars because the sun’s image through the filter is still quite bright. A camera adapter will ensure a firm connection between camera and telescope.