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Solar Eclipse 2017!
August 18, 2017 by Andrew Yee

On Monday August 21 all of Canada will experience a partial solar eclipse of various degrees as shown in the map below (full resolution of the map is available here). The further south a location, the greater extent of the partial eclipse.

In Greater Toronto Area partial eclipse will start at 1:10pm EDT. Maximum partial eclipse will be at 2:32pm EDT, when the Moon blocks 70.8% the area of the disk of the Sun (the technical term is eclipse obscuration). There will be no noticeable brightness change of the surrounding, it will be as bright as on any other afternoon at the same hour with the same weather condition. The entire partial eclipse will end at 3:49pm EDT.

Map source:

SAFETY WARNING: Do not look at the partially eclipsed Sun through stacked sunglasses, multiple layers of exposed film negative, darkened bottle and smoked glass, photographic polarizing and neutral-density filters, and other similar items that appear to reduce the brightness of the Sun. None of these items adequately cuts out the invisible infrared radiation which can permanently damage your eyes. It is still not safe to use any of these items to view the partially eclipsed Sun if there are clouds in the sky.

The only safe equipment to use to view the eclipsed Sun directly is shade no. 14 welder’s glass and certified solar viewing glasses. Shade no. 14 welder’s glass is hard to find. Few welding equipment companies stock the glass because it is used in high temperature arc welding and the glass is too dark for other kind of welding work. For special solar viewing glasses, on the market there are uncertified glasses that do not meet the safety specifications.

An interesting way to view the partial solar eclipse is to make a pinhole projection camera. Remember the pinhole is used to project an image of the partially eclipsed Sun on a surface. NASA has a special eclipse website with extensive resources on how to safely view the eclipse and make a pinhole camera.

An even simpler way to have a pinhole projection camera is to use a hat with many small holes or a colander. Even a tree becomes a giant multiple pinhole projection camera. Gaps among the leaves act like pinholes and project many images of the partially eclipsed Sun.

Clear skies and happy eclipse observing!

Andrew Yee, Astronomer

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