Astra’s Eclipse Guide

Solar Eclipse Safety

A total solar eclipse is one of the most exciting astronomical events. Some people travel all over the world just to find a few minutes of totality. But the rays of our Sun can damage our eyes if we look at it directly. Indeed, before proper protection was developed, some astronomers in the past lost their vision looking at the Sun. Do not use homemade filters to look at the Sun!

Today we can protect ourselves and still enjoy views of the Sun using proper equipment. Remember that failure to use safety precautions can lead to permanent eye damage or blindness!

On this page: Intro - Indirect Viewing | Eclipse Glasses | Astronomical Equipment | Other Safety Considerations | Eclipse Safety Resources

Indirect Viewing

The best method for observing solar eclipses is the indirect method called, "pinhole projection". By passing sunlight through a tiny opening, an image of the Sun can be focused on a plain background. Do not look directly at the Sun through the pinhole. A pinhole projector like this is also called a pinhole camera.

Make Your Own Pinhole Projector

Take a piece of cardboard or thick paper and punch a small hole near the middle, using a pin or needle. The smaller the hole, the sharper the projected image will be. Standing with your back to the Sun, hold the cardboard with the pinhole above your shoulder, allowing sunlight to pass through the pinhole. Position a second piece of cardboard, or other flat surface, several feet away from the pinhole. The image of the Sun will be projected onto this surface. By adjusting the distance between the pinhole and the flat surface, a clear and focused image of the Sun should appear.

Eclipse Glasses

Eclipse glasses can be made of hard plastic or paper. Plastic glasses work much like sunglasses, but they are special. If you use these, make sure they are certified safe by the International Organization for Standardization (ISO) or Conformité Européenne (CE). Before using, inspect them for any imperfections. You can never be too careful with solar filters!

Paper eclipse glasses are widely distributed but be careful, make sure that they are ISO and CE certified. Make sure you order them from a well-known source because they can be counterfeited. Inspect them carefully for pinholes. Hold them up in front you, several inches from your face and aim them toward the Sun (without looking directly at the Sun, of course), you can see if sunlight obviously passes through any pinholes. When you wear them, they should produce a comfortable image of the Sun, without any haziness. Never use defective glasses to view the Sun!

Equipment for Safe Eclipse Viewing

Solar filters especially designed for telescopes are available. Glass or Mylar filters may be mounted on the front of a telescope to minimize the light that enters the system. Since the Sun will not require a lot of magnification, some astronomers will use a solar filter with an aperture stop. Do not use filters that work at the eyepiece. It is safe to project the image from a telescope by removing the eyepiece or replacing the eyepiece with a screen. Do this with caution however, because some telescopes use more than one lens and they may be glued together. The extreme heat from the Sun will melt that glue, so be sure your system doesn't rely on an adhesive. Never look through the system without the protection to point the telescope at the Sun! Most astronomers rely on the appearance of the shadow from the telescope to point the system at the Sun.

The best solar filters for telescopes are hydrogen-alpha filters, abbreviated as Hα. These specialized filters are designed to observe the Sun in a specific wavelength of light known as the Hα spectral line. This type of filter is a narrow-band pass filter, that allows only the visible red light of hydrogen to reach the eye. Today H-alpha filters are affordable for amateur astronomers and they are used widely. Each filter allows a specific small range to pass. With this filter there are many features of the Sun that might be seen on the Sun's chromosphere such as thread-like filaments, solar flares, granules, and other features that are associated with sunspot activity. It is also important that you are familiar with your instrument, so test it out before the eclipse. Even if you've observed other solar eclipses, it really pays to work with your equipment ahead of the event.

There are also solar telescopes available. These are fairly expensive, but should be used if serious solar observing is the goal. Celestron sells its products with solar safe filter technology under the brand name, "EclipSmart". The Daystar Solar Scout is a 60mm dedicated solar telescope. The list goes on, but we haven't done an in-depth study of solar telescopes. Perhaps this best left for a future page.

Other Special Equipment

Other Solar Eclipse Safety Considerations

Don't neglect to protect your skin from the Sun while you are observing that solar eclipse! Yes, the sky will be dark at totality, but it is quite exciting to watch as the Moon crosses the disk of the Sun. If you are using a telescope or other magnification, the disk may be full of interesting sunspots. You may be hanging out in the Sun for several hours to view the whole eclipse. Make sure you have sunscreen, especially for your face and don't forget to use it. A hat will help as long as it doesn't interfere with instruments you will be using.

Wear protective clothing and be sure there is a place that you can rest out of the Sun for a while, if you watch the whole eclipse. Make sure you have access to water and other facilities. Umbrellas and chairs might be among the equipment you choose. If you go to a remote location, you will want to bring along food as well as water and other liquids. Be mindful of possible pests, insects or animals.

Although safety is important for human eyes, don't neglect to protect your equipment. Cellphones and handheld cameras can be damaged by the Sun if they are not protected. Don't let them be exposed to the Sun too long. No exposure without proper protection is the best route to take.