Solar Eclipse May 20

Solar Eclipse May 20

In the afternoon of May 20 we will experience an impressive eclipse of the Sun.  In Page, Arizona and in Saint George, Utah the eclipse will be “annular” – the Moon will pass centrally across the Sun but will leave a narrow ring of the Sun completely surrounding the Moon.  It will not be annular here in Southern California, but it will be impressive nonetheless with the Moon covering 84% of the solar disk.

The Moon will begin to encroach on the Sun’s disk at 5:26 p.m. and maximum eclipse will occur at 6:39 p.m. with the Sun appearing as a thin crescent 13 degrees above the western horizon.  The eclipse ends at 7:43 p.m., about at sunset.

Even though the Sun will be 84% covered, you must use a proper filter to look at the Sun directly you must not look at the Sun directly without a proper filter!  A simple filter made of metalized mylar film can be obtained from Scope City, 3033 Bristol St., Ste J, Costa Mesa 92626, (714) 957-6900.  Please call for their hours;  they are closed on Thursdays.  A welder’s filter glass also can be used, but it must have a rating of 13.  Whatever filter you use, if you can see anything through it when simply looking at surrounding landscape during the day, it is not dense enough.

A day or more beforehand, find a spot where you have an unobstructed view of a fairly wide span of the western horizon – remember, at max, the Sun will be only one-seventh of the way up from the horizon toward the zenith.  (On the coast could be good – but watch the weather forecast;  an on-shore breeze could bring fog and low clouds.)  If there is a moderately large blank, light-colored surface, such as the side of a house, which faces west and if there is a tree or other large plant ten or fifteen feet from that surface located so that at eclipse time it would produce dappled sunlight on the surface, then near max eclipse you will see the usual dappled effect replaced by dozens of overlapping crescents, a rather startling effect.

If you have an inexpensive telescope or binocular, you may aim the instrument at the Sun while holding a white board 15 to 20 inches behind the eyepiece.  Aim the instrument by watching its shadow on the board DO NOT UNDER ANY CIRCUMSTANCES TRY TO LOOK THROUGH THE INSTRUMENT!!!  Doing so can blind you in less than a second!  You may have to focus the instrument to get a sharp crescent projected on the board.  (The reason for suggesting an inexpensive instrument is that a better instrument may produce enough heat within the eyepiece to damage it.)  Practice this before max eclipse so that you don’t have to fumble around later.  If you obtain a nice sharp image, you may even be able to spot a sunspot or two.  Good luck and hope for reasonably clear skies.

Contributed by Carroll Slemaker, OLLI Science Committee Member

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