Never look at the sun with unprotected eyes. Intense exposure to electromagnetic radiation can destroy your retina (the cells that line the back of your eye) and cause permanent eye damage, so it's important to protect your eyesight while viewing any astronomical phenomenon involving the sun.
Specially manufactured solar viewing glasses reduce all forms of light that are known to cause damage to the eyes. Be aware that they are made of a thin polymer plastic that can be scratched or damaged. Do not use the filter if you suspect is has been damaged.
Do not use sunglasses, smoked glass, exposed film or CD/DVDs as filters. While these objects may reduce the amount of visible sunlight your eye receives, they don't significantly reduce the amount of UV light or x-rays.
An alternative is number 14 (or greater) welding glasses. Do not use the glasses if they have been damaged, or you are unsure of their rating.
If you own a telescope, there are a range of solar filters available such as Baader folm and Hydrogen-alpha. The latter type allows you to see the structure of the sun, such as prominences and flares, in fine detail. You should only use filters that attach to the front of the telescope which filter light before it enters the tube. Never use filters that attach to the eyepiece. Naturally you cannot use your telescope's viewfinder. Make sure the viewfinder has the cap securely attached (or even remove it entirely just to be save) so that you cannot look through it or so the sun cannot accidentally burn you through it (I tape the cap on just to make sure).
Southeast students, faculty, and staff can pick up solar glasses at the designated locations with their Redhawks ID. Solar glasses will be available during the events at Houck Field and River Campus for members of the University community and the general public while supplies last.
There are a number of ways you can indirectly view the sun. All involve some form of projecting the sun's image onto a viewing surface.
The simplest method is to make a pinhole camera. Using a sharp pin, poke a small hole in a piece of stiff cardboard. Stand with your back to the sun and hold the card up, allowing light to pass through the hole and project onto a flat surface that is in the shade. Never look through the pinhole at the sun. The greater the distance between the pinhole and screen the greater, but fainter, the image will be.
This method is extremely good at showing large sunspots or the partial stages of a solar eclipse.
If you are close to or on the eclipse path, look at the shadows of the leaves of trees near maximum eclipse. You will see lots of little crescents as the gaps between the leaves act like little pinhole cameras.
To see a larger, brighter image, you can use a pair of binoculars or a viewfinder to project the image of the sun. You can project the image of the sun onto a wall or onto a piece of white cardboard attached to a chair or some other movable object so the projection surface can be moved as the sun moves across the sky. I use a length of dowel to attach my cardboard view screen to the binoculars.
To make viewing easier, you can put a cardboard disk or square around the binoculars so the projected image is in the shadow.
Never look at the sun through the binoculars. Also, make sure that onlookers and young children do not try to look through the binoculars while you are showing them the projected image.
You can use a tripod and attachment to fix the binoculars in place, but be aware that the heat from the sun passing through it may cause damage to the glue and lenses so give them a break ever so often.
You can also use a telescope to project an image. This will give you quite a detailed image and is good for watching sunspots being covered by the encroaching moon. Here it is best to attach the projection screen to the telescope as the image will drift significantly. Again, you have to be careful that the heat will not damage the telescope (reflecting telescopes are at risk of the secondary mirror being damaged), and that other people will not accidentally look into the projecting eyepiece.
If you have a large group of people and a refracting telescope, a good projection system is the sun funnel. Here the image is projected onto the back of a special screen. This allows lots of people to see the image with no danger of accidentally viewing the unfiltered sun.
Looking directly at the sun is unsafe except during the brief total phase of a solar eclipse (totality, when the moon entirely blocks the sun's bright face). The only safe way to look directly at the partially eclipsed sun is through special-purpose solar filters, such as "eclipse glasses" or hand-held solar viewers. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the sun. To date, three manufacturers have certified their eclipse glasses and hand-held solar viewers meet the ISO 12312-2 international standard for such products: Rainbow Symphony, American Paper Optics, and Thousand Oaks Optical.
Totality is safe to look at, and in fact, to experience the awesomeness of the event, you must look at the sun without a filter during totality. If you are within the path of totality, remove your solar filter only when the moon completely covers the sun's bright face, and it suddenly gets quite dark. Experience totality, then, as soon as the bright sun begins to reappear, replace your solar viewer to glance at the remaining partial phases.
You won't need a telescope. One of the great things about the total phase of a solar eclipse is that it looks best to naked eyes. The sight of the corona surrounding the moon's black disk in a darkened sky is unforgettable.
Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars, or other optical device. Similarly, do not look at the sun through a camera, a telescope, binoculars, or any other optical device while using your eclipse glasses or hand-held solar viewer - the concentrated solar rays will damage the filter and enter your eye(s), causing serious injury. Seek expert advice from an astronomer before using a solar filter with a camera, a telescope, binoculars, or any other optical device.Statement on Eye Safety