Thursday, July 6, 2017

BE SAFE!!! Don’t Misuse Solar Eclipse Viewing Glasses

  -- And Other Safe Ways to View a Solar Eclipse -- 

Viewing a solar eclipse improperly can put your eyesight in danger.  With the upcoming eclipse on August 21, now is a good time to discuss various methods to see the eclipse safely.

By now, everyone has probably heard about the special eclipse viewing glasses being made available.  At the Anderson Jockey Lot, 1000 pairs of these glasses will be given away on the day of the eclipse (yes, at NO charge) as long as supplies last.  Many organizations and companies are also offering such glasses for free as a public service.  These glasses are only needed during the period of the eclipse when part of the Sun is not covered by the Moon’s disk.  The only time you can safely look at the eclipse directly without the special glasses is during the scant few minutes that the disk of the Sun is fully hidden (at totality).  Indeed, during that brief totality you are encouraged to look directly at the eclipse to get the full effect in all of its glory.  The special glasses will be needed again as soon as totality is over, should you continue watching the Sun.

However, it is necessary to use the glasses in the way the manufacturer recommends to properly protect your precious eyesight!  Even when looking through the special eclipse glasses, you should observe the Sun for no longer than 3 minutes at a time with at least a 20-minute break in between each 3-minute observation.  Indeed, you will not miss anything by not looking at the Sun frequently before totality, because the Moon’s disk will gradually cover the Sun’s disk at a very slow imperceptible rate.  Those who wear prescription glasses should place the eclipse glasses in front of their regular glasses, as I am pictured doing in the above photo.

But there are safe ways to constantly view the eclipse, even before and after totality.  Those of you who have read one of my earlier articles know that you can see all the sunlit periods (called partial phases) of the eclipse by looking in the shade cast by a leafy tree.  If there is not a tree around, you can use a common kitchen colander.  The holes in that utensil will project nice multiple images of the eclipsing Sun  onto any surface you choose if hold the colander far enough away from the surface.

NEVER look at the Sun directly through binoculars or a telescope at any time, whether there is an eclipse or not.  However, if you own either of those, there is a safe way to use them to observe the solar eclipse.  If using binoculars, it is best to use an adapter (available for a few dollars) to mount the binoculars to a camera tripod.  Again, DO NOT LOOK AT THE SUN DIRECTLY THROUGH THE BINOCULARS.  While holding a white piece of cardboard behind the binoculars, tilt the binoculars with the mount until you see the shadows of the binocular’s tubes as perfectly round circles. At that time, the binoculars will be pointing directly at the Sun.  Now, move the cardboard far enough away from the binoculars for the Sun’s image (projected onto the cardboard by the binoculars) to appear at least 3 inches wide.   Looking at the image of the Sun, focus the binoculars until the disk of the Sun is sharp around the edges.  Click here to see a photo such a binocular projected image.

The same technique can be used with a small telescope, but the telescope should have a main lens or mirror no wider than 3 inches (75 mm) to avoid overheating.

Another way to safely observe the eclipse with binoculars or telescope is to buy professionally made full-aperture filters.  This method may be the easiest and most convenient way to use a telescope or binoculars to observe the Sun.  Here are a couple of sources: Thousand Oaks Optical and Orion Telescopes.

I hope you have found this article useful.  Have fun experiencing the once-in-a-lifetime total solar eclipse, but most of all, stay safe.  You are invited to join us at the Anderson Jockey Lot where we will have the longest totality along the I-85 corridor lasting 2 minutes and 40 seconds!