Preparing for the April 8 Solar Eclipse: Projection
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One of the best ways to watch the April 8 solar eclipse is by using official eclipse glasses that provide protection to the eyes. No one should ever look directly at the Sun without wearing eye protection because permanent eye damage and even blindness can occur. File photo
DAN SLAIS, Retired Science Teacher
This is the seventh in a series of articles by retired science teacher Dan Slais to help Parkland residents prepare for the April 8 solar eclipse that will be visible in southeast Missouri. – Editor
To enjoy the approximately three hours of the total eclipse on April 8, one must prepare a way to look at the Sun without endangering the eyes.
Eclipse glasses, which are available at many sites, #14 welding glass, or solar filters are all excellent possibilities; however, several projection methods may be helpful, as well.
The old-fashioned handheld pinhole projection method is the easiest because it’s simple and easy to set up. Telescope and binocular projection can work, but care must be taken, especially when magnifying the Sun. The goal is to keep safe!
Note that pinhole projection does not mean looking at the Sun through a pinhole!
The steps to make a pinhole projector are as follows:
– Take a sheet of paper and make a tiny (pin-sized) hole in the middle of it using a pin or a thumbtack. Make sure that the hole is round and smooth.
– With your back towards the Sun, hold the paper with the pinhole above your shoulder, allowing the Sun to shine through.
– The second sheet of paper will act as the projection screen. Hold it at a distance, catch the sunlight, and you will see an inverted image of the Sun.
– To make the image of the Sun larger, hold the screen paper further away from the paper with the pinhole. You are not looking at the Sun. You are looking at a projection of the Sun on a piece of paper.
Compared with pinhole projection, optical projection generally provides bigger, brighter, sharper images. Optical projection uses a telescope or binoculars to project images of the partially eclipsed Sun onto a surface for convenient viewing. Optical projection involves optics, i.e., lenses and/or mirrors.
The following are steps for setting up a projection for a Reflecting Telescope:
– First, take the spotter scope off the telescope.
– Place the telescope on a tripod with the open end facing the sun.
– With your back toward the Sun, use the shadow of the telescope to center the view.
– Place a white poster board on an easel opposite the eyepiece.
– Light will go through the scope and be magnified on the poster board. It can be focused with the knob at the eyepiece. The distance can be changed to maximize the size of the projection.
– A dark-colored pencil will smoke and catch on fire if placed where your eye would normally be placed at the eyepiece. That should make quite clear the importance of not looking through the eyepiece and/or a telescope. To show the heat of the light produced by the magnification of the telescope, it might be a far better plan to cook hotdogs at lunch.
– The round perception of the bright Sun will show the shadow of the Moon crossing and producing the eclipse. Do not leave your scope unattended. It is basically a two-man setup, with one working the scope and the other handling a poster board.
This can work with a refracting telescope or binoculars. Be sure to block one side of the binoculars to avoid difficulties. The heat of the Sun coming through the lens can build up. One should be careful in handling the lens and eyepieces. First, check for heat. If it is getting hot, stop the operation for a time and allow the surface to cool down. Again, the white poster board is catching the light, not your eyes.
Remember to always keep your back towards the Sun while looking at a pinhole or optical projection. Normally, the telescope eyepiece that provides less magnification (25mm) is best to use. Some of these setups can be practiced before the eclipse date to increase your confidence that the projection will work.
