Some of you may remember the Transit of Venus from June 2012, when the planet Venus — looking like a little black ball — slowly crossed the face of the sun. It was an amazing sight and one of the rarest predictable events in the sky. Unfortunately, the next one won’t be until December 2117. Did you know there are transits of Mercury too? These are a little less impressive because the dot of the planet against the sun is much smaller. They are more common, occurring about 14 times in a century. This next one occurs on Nov. 11, and it is favorable for viewers in the eastern U.S. Locally, little Mercury will crawl across the disk of the sun from 7:36 a.m. to 1:04 p.m.

How do you see it? Your left-over eclipse glasses from 2017 aren’t going to cut it. They do not provide the magnification needed to see Mercury, which will have an apparent size 1/194 that of the sun. Special equipment is needed, and this is where I must remind everyone that looking at the sun through binoculars or a telescope can cause instant, irreversible eye damage. Describing how to properly outfit a telescope for solar observing is beyond the scope (sorry) of this article, but it can be done responsibly. Do your homework, starting with the maker of any telescope you own. They may sell solar filters to go with it. Note that any proper telescope solar filter blocks the light before it enters the optical system. Do not try to combine eclipse glasses with binoculars! Make any plans or purchases soon while there are still a few weeks to prepare. If setting up a solar telescope is not for you, or if the weather does not cooperate, check online for live broadcasts. There will be many.

Ian Clarke is the director of the Hatter Planetarium at Gettysburg College. More information, including a calendar of free shows and field trip details, available at www.gettysburg.edu/hatterplanetarium.

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