Back to Volume
Paper: The Sun Funnel: A Do-It-Yourself Projection Device for Safe Solar Viewing by Groups
Volume: 457, Connecting People to Science
Page: 29
Authors: Fienberg, R. T.; Bueter, C.; Mayo, L. A.
Abstract: Virtually every commercial telescope comes with a warning not to point it at the Sun, since doing so could not only damage the instrument but also injure the observer. Yet the Sun is typically the only astronomical object visible in the daytime, and even in white light it offers much to see in a telescope: sunspots and limb darkening, the partial phases of solar eclipses, transits of Mercury and Venus, and even transits of the International Space Station. Teachers, planetarians, and other science educators who wish to share these phenomena with their students or visitors face a challenge: how to safely show a magnified image of the Sun to many people at once. Using aperture filters on telescopes is fine if you have lots of telescopes, but if you have only a few telescopes, or perhaps only one, the result is long lines at the eyepiece. One inexpensive solution is solar projection, i.e., projecting an image from the telescope onto a wall or screen. But this technique is fraught with danger, as there is always the possibility that someone will look into the bright beam of sunlight streaming from the eyepiece and risk serious eye injury. Here we describe a novel solar-projection device, the Sun Funnel, that fits in a telescope focuser in lieu of a regular eyepiece. It is quick and easy to build using inexpensive, readily available supplies and simple household tools. The Sun Funnel completely encloses the sunbeam coming from the telescope and forms a clear solar image on a rear-projection screen. With this device, many people can simultaneously and safely enjoy a telescopic view of the Sun.
Back to Volume