Making Your Own Solar Filters for the Upcoming Eclipse

Rebecca Jean T.
5 min readMar 13, 2024

As you prepare for the total solar eclipse crossing America next month, you’ve probably heard a lot about solar filters and safely viewing the Sun. Making your own solar viewers can be an affordable alternative to purchasing premade ones, especially as costs rise and items go out of stock leading up to the total eclipse next month. As long as you have solar filter paper and can attach it properly, you can safely use telescopes, binoculars, and cameras to view the Sun.

Image of the sun taken through an amateur telescope. The surface is perfectly round and orange. A few sunspots are visible as faint black smudges.
Image of the Sun taken through a homemade solar filter using a small telescope. Homemade solar filters are made from exactly the same protective solar filter paper that solar glasses and speciality filters are made from, just attached to devices using a homemade frame. Credit: Rebecca Jean T.

Making your own solar filter is relatively simple. All you technically need is solar filter paper that meets ISO 12312–2 (or 12312–2:2015) standards and some way to properly attach it to your device. The key here is to make sure your solar paper completely covers the surface of what you are looking through. Measure the diameter of the first place sunlight will hit your device. For a camera, this needs to be in front of the lens. For telescopes and binoculars, you similarly need to place the filter in front of the optical tube. A solar filter at the eyepiece may stop some sunlight from reaching your eye, but it will not prevent concentrated sunlight from damaging and overheating your telescope.

Once you know what size solar filter you need, you can just purchase a square the size of your device’s diameter. So a telescope with a 4" diameter will need a 4x4" piece of filter paper. You can get pieces larger (and you may have to for binoculars anyway) but just know that you will have to trim larger pieces to fit. Don’t worry about trimming larger pieces into perfect circles, as long as your filter completely covers your device or has a solid frame covering the edges where it doesn’t, it is safe to use.

Two images of a homemade solar filter. On the left the solar filter paper sits in a cardboard frame with a circle cut out in the middle for the filter paper. On the right the filter is covered with a cardboard circle to protect it in storage.
A homemade solar filter for a small telescope. The inner cardboard can be kept to use as a protective cover for the filter when not in use. Credit: Rebecca Jean T.

To make a structure that can hold your solar paper in place, consider making a frame of cardboard for it to rest in. You can simply cut a square frame of cardboard with inner measurements just slightly smaller than your solar paper and outer measurements just slightly larger. This allows you to tape the filter in place on the inside of the frame without special cuts. You can also cut the inner part of the cardboard frame in a circle the same size as your…

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Rebecca Jean T.

Published author on NASA’s Radio Jove project. Researching science topics to deliver to you in bite-sized stories.