Those who have been fortunate to witness a total solar eclipse are familiar with the otherworldly, transformative moment when darkness falls and the Moon blocks out the light from the Sun.
I remember my first total solar eclipse back in 1999. I went with some friends to Stuttgart, Germany, to observe the totality. The experience was not the one that I expected. It was very cloudy and it actually rain, but we could feel the breeze and how the darkness filled the space.
When the sun's corona becomes visible, a glowing halo appears around the darkened disk of the moon, creating a breathtaking sight.
The area where you can observe the totality is quite narrow. The image below represents the areas where you can view the next solar eclipse on April 8 2024, from total (100%) to partial eclipse.
Figure 01: Diagram of the locations where the total solar eclipse on April 8, 2024, can be seen. Source: NASA.
In this article, I’ll describe my recommended setup for public outreach activities to observe a solar eclipse and some interesting activities to do with kids.
Safety
Before we begin, it's crucial to emphasize the safety precautions for observing the Sun. It is never safe to observe the Sun with the naked eye or homemade equipment. Directly observing the Sun with a telescope is extremely dangerous unless you have a professional and suitable filter.
Please note that some inexpensive telescopes may come with a small piece of plastic labeled as a "SUN filter." It is important to never use this filter, as it can cause irreversible damage to your eyes. The best thing you can do with that filter is to throw it in the rubbish bin to prevent accidental use.
Figure 02: image of an unsuitable filter.
Eclipse glasses
If you don't have a telescope, using certified eclipse glasses is a safe way to view the Sun during a solar eclipse. These glasses are designed to block most of the Sun's ultraviolet, visible, and infrared light, allowing you to observe the eclipse without damaging your eyesight. Simply lie down on the floor or sit in a camping chair, put on your certified solar eclipse glasses, and look up. While these glasses enable you to see the Sun with your naked eyes, they do not provide a lot of detail.
Figure 03: Solar eclipse glasses. Source: Baader.
It's important to note that prolonged viewing of the Sun, even with eclipse glasses, is not recommended. It's best to observe the eclipse in short intervals instead. When acquiring solar eclipse glasses, ensure they are certified and from reputable suppliers or astronomy shops. Look for the International Organization for Standardization (ISO) mark and the ISO 12312-2 standard for filters. Before using the glasses, check for any punctures or scratches on the filter. If you find any damage, discard the glasses and obtain a new pair.
Telescope Setup for Public Outreach
There are two main solar filters, glass and film based. In my honest opinion, film solar filters are usually able to deliver better details of the surface of the Sun, but they are too fragile for outreach activities. A tiny scratch or puncture will put someone's eyes at risk and break the course of the activity. If you don’t have a replacement, you may need to cancel the event.Â
High Point Scientific has a very nice video comparing glass and film solar filters. Consider having a look.
My recommendation is to get a glass solar filter or consider using image projection on a white surface. A glass solar filter costs around 100 USD for a relatively small telescope. If you are in a school environment, you can use a whiteboard or a large and inexpensive white cardboard or acrylic panel. This method works extremely well for larger groups, as they don’t need to look through the eyepiece. The image projected onto the white surface can reveal a significant amount of detail regarding sunspots.
Figure 04: Telescope setup using a 90mm Maksutov-Cassegrain telescope on top of a Skywatcher StarAdventurer mount. The Skylabs Polar Alignment Adapter was used for alignment, and the Skylabs solar finder scope was used to locate the Sun. The image is projected onto a white cardboard iMac box.
Either way, the telescope will need to track the Sun. Otherwise, you will need to keep moving the telescope quite often, which can be challenging when you have multiple people around asking you questions. If you are using a star tracker or a regular equatorial mount, you need to align the mount with the celestial pole in the daytime. To achieve that, you can use our Polar Alignment Adapter, which allows you to align your equatorial mount without the need for visual access to Polaris or Octans asterism. You can follow the instructions available in the user guide.
Figure 05: Skylabs Polar Alignment Adapter used to align the equatorial mount in daytime.
Once this is done, you will need to point the telescope to the Sun. Obviously, you can’t use a finder scope. Instead, I recommend using our solar finder scope. This very simple device offers a safe and quick method to locate the Sun using your telescope, without the need to look directly at it. It projects an image of the Sun onto a translucent white screen, visible from both sides, and is compatible with all standard finder dovetail adapters.
Figure 06: Skylabs solar finder scope offers a safe and quick method to locate the Sun using your telescope.
Cool activity to do with kids
Grab a colander or any object with multiple small holes and hold it to project the shadows on the floor or any flat surface. Each hole acts as a pinhole camera, projecting an inverted image of the Sun. The holes don’t need to be round for this to work.
The shadows projected from the colander during an eclipse will generate a myriad small crescents cast in the shadow, corresponding to the eclipsed phase of the Sun.
Figure 07: myriad of small crescents projected from a colander. Credit: Beverly Hartline.
During the eclipse, shadows take on a different appearance, creating an unusual atmosphere. This effect is particularly noticeable when sunlight shines through the leaves of a tree. The gaps between the leaves act as pinholes, casting crescents of light onto the ground in the shade.
You can encourage kids to create those shadows by interlacing fingers leaving small gaps between them. Let the sunlight pass through their fingers onto the ground. During the partial phases of a solar eclipse, you can observe the same tiny crescents being projected onto the floor.
