Viewing Kentucky's total solar eclipse can be a truly amazing experience, but keep in mind there are certain risks associated with eclipse viewing. Special attention should always be paid to safety to ensure a happy viewing experience. To avoid potential accidents or health problems, here are some things you need to remember before turning your gaze to the sky August 21, 2017.
While this may seem to be common knowledge, it should be pointed that the sun is an extremely bright celestial object. In fact, it is approximately 120 billion times brighter than stars of the first magnitude and 460,000 times brighter than a full moon. As a result, there is a very real risk of causing serious damage to the eyes if you stare directly into the sun for even the shortest amount of time.
While the sun may appear darker through sunglasses or other filtering devices, this is only because the visible light has been weakened. Infrared radiation, which is harmful to the eyes, is usually not shaded. Since the human eye does not feel the brightness of infrared radiation, serious damage could be occurring undetected.
Fortunately, a total solar eclipse can be viewed when the sun is blocked out in totality, so for two minutes and 40 seconds those viewing the August 21, 2017 eclipse will be able to get a good look at this natural phenomenon. It is important to remember, though, that partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions.
Before we get into the proper ways to view a total solar eclipse (and the equipment required to do so), let’s examine a few ways that are incorrect and potentially hazardous.
First a foremost, the sun should never be looked upon directly with the naked eye. Even sunglasses do not provide enough protection to view the sun directly. The sun should also not be viewed directly using a telescope or binoculars. Those wishing to take photos of an eclipse should not aim their viewfinders directly at the sun. Problems ranging from retina problems to even eyesight loss could occur if the sun is viewed incorrectly.
According to NASA, “Even when 99 percent of the sun's surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection.” As mentioned above, an eclipse can be viewed when the sun is blocked out in totality, but there are precautions that can be taken to reduce the risk of eye damage outside of the two-minute, 40-second window that will occur August 21, 2017.
The safest and most inexpensive way to prevent eye damage while viewing an eclipse is by using projection. With projection, a pinhole or small opening is used to form an image of the sun on a screen placed approximately three feet behind the opening. Multiple openings can be used to cast a pattern of solar images on a screen. These items can be created with perfboard or a loosely-woven straw hat or even interlaced fingers. Overlapping leaves from a broad-leafed tree can create crescent-shaped images on the ground. Binoculars or a small telescope mounted on a tripod can also be used to project a magnified image of the sun onto a white card. While this offers a way to view partial phases of an eclipse safely, care must be taken to ensure no one looks through the device. The main advantage of any type of projection method is the no one is looking directly at the sun.
Filters designed specifically to protect the eyes are also available. Most of these filters feature a thin layer of chromium alloy or aluminum deposited on their surfaces to reduce both visible and near-infrared radiation. One of the most widely available filters for safe solar viewing is shade number 14 welder’s glasses, which can be obtained from welding supply outlets. An inexpensive alternative is cardboard-framed glasses with lenses coated in aluminized Mylar manufactured specifically for solar observation (Note: This is not the same aluminized Mylar used in “space blankets” or the type used in gardening.)
Some experienced solar observers use one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density. The metallic silver contained in the film emulsion serves as a protective filter. Some of the newer black-and-white films use dyes instead of silver, however, which makes them unsafe for using as a filter. Also, black-and-white negatives with images on them should not be used. Some solar observers have even used floppy disks and compact discs as protective filters, covering the central openings and looking through the disk media. The viewing quality when doing this can be relatively poor, however, and some CDs made with very thin aluminum coating are not safe to use.
While there are definite precautions that need to be taken when viewing a solar eclipse, the danger also exists of being so cautious you may actually miss out on the best parts of the experience. Remember, the total phase of an eclipse can (and should) be viewed without any filters whatsoever, so make sure you don’t miss a moment of this truly unique natural phenomenon!