Easy Guide to Viewing an Eclipse

In anticipation of the upcoming total eclipse on April 8, 2024, astronomer Terry Richardson has developed a cost-effective, safe and easy-to-build gadget for solar viewing. Known as the Safe Solar Viewer (SSV), the device projects sharp, magnified images of the sun onto a screen, a superior alternative to traditional cardboard pinhole viewers.

Richardson, a faculty emeritus of the College of Charleston in South Carolina, designed two versions of the SSV. The simpler version uses optics costing around $1, obtained from a pair of +1 reading glasses available at dollar stores. The focal length of the lens is approximately 39.4 inches (1 meter) and is determined by projecting the light from a room lamp through the lens onto a wall and measuring the distance at which the image is sharpest.

The SSV requires a long three-sided cardboard box, which should be around 6 or 7 inches (15.2 or 17.8 cm) longer than the lens focal length. After cutting a small, round hole in the center of the box end, the reading glasses lens is placed over it and secured with masking tape, duct tape, or glue. A white card is then glued at the opposite end of the box to serve as the projection screen.

The advanced version of the SSV employs two lenses, an objective lens and a Barlow lens, to project an image onto a white screen. The lens set costs around $5 and the device’s frame is preferably made of plywood to maintain alignment of the lenses. The objective lens should have a focal length between 400 and 600mm, while the Barlow lens should be between 18 and 30mm.

Both versions of the SSV are safe for solar viewing and can be easily made at home. They offer a practical solution for those without access to telescopes or binoculars, making solar eclipse viewing accessible and affordable. Apart from being a useful tool for solar viewing, building the SSV also serves as a valuable STEM project for parents, science classes, clubs, and Scout groups.

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