lunar eclipse

Solar Extravaganza- Total Eclipse 2017

by Marcia Dettloff, OD on July 18, 2017

Update 8/14/17  We are all OUT of solar specs. Thanks to your donations we collected $768 for Triangle Down Syndrome Network!  Unfortunately, there have been reports of substandard solar specs and even counterfeit products.  The American Astrological Society (AAS) has a list of reputable sources of solar viewers. From their updated guide  “Safe solar filters produce a view of the sun that is comfortably bright (like the full moon), in focus and surrounded by black sky. If you glance at the sun through your solar filter and find it uncomfortably bright, out of focus and surrounded by a murky haze, it’s [the viewer is] no good.”  If you don’t have solar glasses to safely view the eclipse directly, check out the links below for simple DIY projects that will allow you to safely view a projected image of the eclipse.

Since the last total solar eclipse in the US was in 1979, I had to settle for my photo of the 2015 blood moon lunar eclipse. But on Aug 21, 2017 a total solar eclipse will be visible across a large swath of the US and the entire US will see at least a partial solar eclipse. You don’t want to miss this once in a lifetime opportunity! I still remember the strange shadows on the grass and how surreal it was getting dark in the middle of the afternoon as I was walking between college classes during the eclipse in 1979 (where the obscuration only made it to 79% vs. the 93% we will experience in Cary).

While supplies last, we will be giving out ISO 12312-2 certified solar glasses from Thousand Oaks Optical for a donation of any amount to the Triangle Down Syndrome Network. Please stop by our office to get yours now.

Although a solar eclipse is an amazing experience, you need to be prepared in order to safely enjoy the eclipse. NEVER look directly at the sun without using special solar glasses (or shade 12 or higher welding filters) that block 99.999% of the sun’s visible light along with IR and UV blocking. Without protection, the intensity of the sun’s rays can cause damage to the retina that can result in permanent vision loss.  If you think you can safely take several quick peeks throughout the course of the eclipse, think again. The effect is cumulative and it only takes a combined total of 60 secs of exposure to cause damage.  Here’s a retinal photo of a Canadian friend of mine that has a macular scar in both eyes from looking at the eclipse of July 20, 1963 without solar glasses.  The scar is in the crescent shape of the eclipsed sun!

Here are some other safety tips:

  • The ONLY time you can view the sun without the filters is during the very short period of totality when the sun is totally blocked by the moon. At that point you will have to take off your solar spectacles to see anything because it will be dark. But you need to put them back on as soon as the sun pops out the other side. Since we are not in the Path of Totality, it will NOT be safe to view the sun without solar glasses during any part of the eclipse.
  • NEVER view the sun with binoculars or a telescope using the solar spectacles. They may get knocked off by the equipment. More importantly, the lens will magnify the intensity of the sun’s rays and can damage the solar spectacles or the equipment itself.  If you are going to use a binocular or telescope to view the eclipse, you HAVE to place a solar filter over the OBJECTIVE lens (where the light comes in), not the eyepiece.
  • A camera will also need a filter in FRONT of the camera lens because the sun will be too bright for the sensors. You also don’t want to be looking through the viewfinder without a filter.
  • Make sure the solar spectacles are free of scratches, pinholes or other defects before using them to view the sun.
  • The American Astronomical Society has a pdf handout with full details on safely viewing the eclipse

Here’s a map showing the path of totality for the eclipse. You can click any location to see the eclipse details for that location. Subtract 4 hours for our local time (Eastern DST).  The entire eclipse event lasts about 3 hours but only locations within the shaded band will experience totality where the moon totally blocks out the sun for up to 2 ½ minutes and major stars can be seen, like at twilight. Here in Cary, the moon will transit across the sun from 1:16 to 4:05 PM, blocking 93% of the sun at its max at 2:44 PM. That’s much more than what I experienced back in college. And if you are willing to drive 3 ½ hrs to south Carolina or 4 1/2 hours to the NC mountains, you’ll be able to experience a once in a lifetime total eclipse of the sun. At least take a few minutes to look out the window, wherever you are.

DIY projects for viewing the eclipse indirectly:
Cereal box pinhole projector

Science Friday’s 5 projects for viewing the eclipse

AAS Pinhole Projectors

Binocular projection system (for those that want a more sophisticated solution)

Other eclipse links:
Excellent explanation of all the phases of the eclipse and what to look for when at eclipse.aas.org

Simulation of eclipse  look up the local time for the eclipse by town/city and see a simulation of the effect at that location

NASA Safety Tips

Washington Post article shows what can happen when eclipse is viewed without proper protection

Astro-physics.com  Source of solar filters for cameras, binoculars and telescope and solar film for DIY filters

Youtube DIY instructions  for a solar filter for your camera

Megamovie citizen science project- take a picture that will be combined with other images along the path to make a video of the entire eclipse

American Astronomical Society

NASA Eclipse Info

Great American Eclipse

Astronomy magazine

Sky and Telescope

Eclipses for the next 10 yrs

 

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