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How to Watch Mercury's Journey
By Andrew Bridges
Chief Pasadena Correspondent
posted: 04:01 pm ET
12 November 1999
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mercury_howto_991104With or without a telescope, there are several ways to view the November 15 Mercury transit of the sun. First off, experts warn that improper viewing of a transit -- like a solar eclipse, or the sun on any normal day -- can cause severe damage to the eyes, even blindness. (And since Mercury is only 1/195th the diameter of the sun, it would not be visible to the naked eye in any case.) Perhaps the easiest way to watch the transit of Mercury across the sun is on the internet on streaming video delivered via one of any number of links. Otherwise, many planetariums and observatories across the country, including the Griffith Observatory in Los Angeles, plan to hold transit parties where telescopes -- equipped with the proper solar filters -- will be set up for viewing by the general public. Astronomers using their own telescopes should make sure they have good solar filters -- made of aluminized glass or aluminized Mylar -- before attempting to view the transit. Patrick So, an astronomical lecturer at the Griffith Observatory, said the safest way to view the transit with a small telescope -- even without use of the filters -- is to avoid looking directly into it at all. Instead, So said, viewers should hold a screen made of white paper or cardboard below the eyepiece, allowing the telescope to project an image of the sun onto it. To adjust focus, simply move the screen back and forth. By stopping down the aperture, you can compensate for the suns brightness. And take care to avoid the light directly as it strikes the screen -- like the light concentrated by a magnifying glass, it can burn your skin. Mercury will begin its transit at 4:15 p.m. ET and end at 5:06 p.m. To find the point where the planet will make first contact with the sun, So said, first determine which way the sun is drifting, i.e. toward the west. Then travel around the sun's disk counterclockwise 123 degrees to a point that should put you at about 11 oclock -- that should be where Mercury first begins its transit.
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