2017 Great American Eclipse - Methods and Equipment to Watch the Eclipse
(Michael Zeiler, www.GreatAmericanEclipse.com)
The ONLY time you can view the eclipse with your naked eye is during totality. The corona and any prominences will be visible, and safe to view, unaided. The sun is so intensely bright that PERMANENT DAMAGE can be done to your eyes if you look directly at the eclipse even up to 99% coverage. There is still plenty of action during the eclipse besides totality. Watching the shadow disk slowly creep along the surface, seeing Baily's Beads, and witnessing the Diamond Ring Effect are breathtaking to behold. There are plenty of options to view these stages of the Eclipse safely. The two primary methods are via Projection and Filtration.
How to View the Eclipse by Projection
Projection viewing is done by punching a small hole (about 1mm) in any piece of tin foil or cardboard. You can then mount the foil or piece of cardboard onto a larger piece of cardboard or something sturdy to hold. Then hold your pinhole projector so that the sun is behind you, and the projector is flat against the direction of the sun. Have another sheet of cardboard, other flat surface, or even the ground to project the image onto. That's it! You'll be able to see an image of the sun projected through the pinhole onto the second surface. DO NOT LOOK DIRECTLY AT THE SUN THROUGH THE PINHOLE. The size of the image depends on the distance between the pinhole and the surface, so have fun experimenting.
(http://www.imagen-estilo.com/images/articles/pinhole_full1.jpg)
This method can work with any small hole that you can then project onto some other surface. A standard kitchen colander will work, and gives many separate images of the eclipse: one for each hole in the colander.
(https://dyer.vanderbilt.edu/wp-content/uploads/sites/63/photo1.jpg)
With a bit of practice and patience, you can even get a projection through your own interlaced fingers.
(https://eclipse.aas.org/sites/eclipse.aas.org/files/Waffle-Fingers_RTF_512x323.gif)
The other projection method is with your own telescope or binoculars. BE VERY CAREFUL USING THIS METHOD: THIS CONCENTRATES THE SUN'S RAYS AND CAN CAUSE PERMANENT DAMAGE. With your binoculars, cover one side with a cap. Then point the now single-sided binoculars at the sun. DO NOT LOOK THROUGH THE BINOCULARS, THIS IS PURELY A PROJECTION TECHNIQUE. Place a sheet of paper or other flat surface further away from where you would normally look through your binoculars.
You will want the projection surface to be pretty far away from the eyepiece. If your projection paper is close such that the sun's beams form an actual focus point, then this can increase the risk for fire (think of melting crayons with a magnifying glass. This is exactly what to AVOID).
AGAIN, NEVER LOOK THROUGH YOUR BINOCULARS OR TELESCOPE UNFILTERED WHILE IT IS POINTED AT THE SUN!!!
(http://spaceweather.com/sunspots/images/binocularprojection2.gif)
Especially with telescope eclipse projection, it can be useful to attach a piece of cardboard around the telescope to provide a shaded area on the paper or other surface that you are projecting onto. This helps with the contrast of the image to more clearly see the progression of the eclipse.
(https://eclipse.aas.org/sites/eclipse.aas.org/files/S&T_Telescope_Projection.jpg)
How to View the Eclipse through Filtration
There are a variety of types of filters and systems that allow you to view the eclipse in all of its stages, as well as the full sun. First and foremost you CANNOT LOOK AT THE SUN OR THE ECLIPSE WITH STANDARD SUNGLASSES. Even those that block UV radiation will not suffice to protect your eyes. Viewing the sun or Eclipse with sunglasses can cause PERMANENT DAMAGE even before you physically feel any discomfort or pain. Solar filters that adequately protect your eyes must meet very precise specifications.
Furthermore, due to the required preciseness, all filters must be in pristine condition. Any scratches, holes, or other opening in the filters, no matter how small, will let in enough light to cause permanent damage to your eyes.
There are also two different kinds of filters for viewing: narrowband and white light (broadband). The following filter options are all white light filters. These block all but a very very small percentage of light, but allows the full spectrum of visible light through. These are great filters to see sunspots and all phases of the eclipse.
The easiest and most straightforward solar filters are Solar Viewers. These glasses look like old style 3D glasses, but instead of red and blue elements, they have sun-safe polymer filters that allow you to look directly at the sun. Just completely cover your eyes and view away! There are also various solar viewing specific binoculars. All of the protection and correct filtration elements are permanently manufactured within the binoculars. They are an excellent grab-and-go option that also provides some magnification.
If you already have your own standard binoculars or telescope, there are also solar filters that you can place over the front objectives. These filter out or reflect the vast majority of incoming light, allowing you to view the sun with your own optical setup. These are white light filters just like the glasses and binoculars above. You can witness the entire eclipse, and view the sun anytime it is out and be able to see any sunspots on the surface. These filters allow you to use your standard eyepieces as normal, affording all of the great magnification that you have become accustomed to. The filter material is available in loose sheets so you can make your own filters to match any aperture sizing you have in your collection. Finally, on some types of telescopes, there are wedges and filters that you can place on the back of your scope. These Herschel Wedges and the Quark system will not work on all telescopes. Please double check or ask us if you are unsure what will work for your system.
As a caution for using this solar film or any type of filters, just to reiterate: The film must be in pristine condition. Any scratches or holes, no matter how small, will let in enough light to damage your optical system, and cause permanent damage to your eyes.
Finally, for your viewing pleasure, there are dedicated solar telescopes. These can be used during the solar eclipse (though they will filter out too much light for use during totality) as well as anytime the sun is out. The options below filter out all of the incoming light from the sun except for a very narrow range of visible light, called Hydrogen Alpha (Ha). This range of light brings out the granularity of the sun's surface, any magnetic veins and other surface activity, as well as any flares or prominences. These sorts of details will not show up with white light filters. Ha telescopes can make the sun pop in a way nothing else can:
(http://www.365astronomy.com/images/D/2016-04-18-1011.8-Ha_g2_ap10.jpg)
There are plenty of options for any situation to enjoy all phases of the eclipse and the sun in general when it is out and shining. Remember to be safe and responsible in the sun. From all of us here at Cloud Break Optics, good luck and clear skies!
P.S. Stay tuned for the next blog post in which we discuss the gear and methods to photograph the solar eclipse!
