That experience inspired my first amateur research project. Every day that summer at precisely 11:00 A.M., I set up my telescope and carefully sketched the sunspots on a piece of graph paper. I quickly discovered that the sun's surface, unlike the earth's, rotates at different rates depending on latitude. Sadly, my intensive investigations soon wore out the scrawny scope. Since then, I've visited our home star mostly through no. 14 welder's glass duct-taped over binoculars and recently via the World Wide Web.

But the total eclipse that will be cutting across Europe and western Asia on August 11 put me on the lookout for better ways to see the sun. So you can imagine my excitement when I learned of an elegant solar projector designed by Bruce Hegerberg of Norcross, Ga. It creates a dazzling daylight display. The so-called limb-darkening effect--that is, the apparent drop in brightness near the sun's edge caused by the longer viewing path through the sun's atmosphere there--is plainly visible. Also, the characteristic structure of sunspots, with a dark inner umbra surrounded by a lighter penumbra, can be clearly seen.

Because the solar image can be easily viewed in daylight by many people at once, Hegerberg's fabulous device is perfect for eclipse watching. Moreover, by presenting such enticing images during the day when it is easiest to reach nonastronomers, this projector could revolutionize sidewalk astronomy--the time-honored practice whereby amateur astronomers set up small telescopes to give passersby a peek at the heavens.

Hegerberg fashioned his first solar projector, the "Sun Gun," from an inexpensive telescope assembly, some PVC piping and a large flowerpot. Those interested in the details should check out his Web site. Here I will describe his second-generation device, the "Sun of a Gun," which can be quickly and cheaply assembled from a paint bucket. If your telescope has a heliostatic (sun-following) motor drive, you'll be able to track the sun's motion for hands-free viewing.

You'll need a plastic five-gallon (20-liter) paint bucket (such as Home Depot part no. 084305355553). Discard the lid and paint the inside of the bucket black to prevent ambient light from coming through the translucent plastic. Cut a 21/4-inch hole in the bottom using a hole saw attached to an electric hand drill. Through the hole, thread a male flexible adapter for a water hose (Ace Hardware part no. 45708) and secure it in place with one two-inch conduit locknut (Home Depot part no. 051411461966). (Obviously, readers outside the U.S. will need to adapt these measurements to a metric equivalent, depending on the availability of hardware.)

Next, drill an 1/8-inch hole about a half-inch from the end of the adapter. Line up this hole with the screw hole in the eyepiece assembly and lock the two together using the screw that normally holds the eyepiece in place. If the adapter does not fit your scope, affix a universal camera adapter (about $30 from Orion Telescopes; 800-676-1343) to your scope and attach the bucket to that.

The sun's image appears on a rear-projection screen of the kind often used in large-screen TVs. Many varieties of screen are available, each with different trade-offs in viewing angle, image brightness, sharpness and contrast. Hegerberg purchases a flexible Da-Tex rear-projection screen for $10 per square foot from Da-Lite Screen Company (800-622-3737). A 15-inch square will suffice. Secure the screen, polished side facing out, over the open end of the bucket. You can use a 48-inch plastic wire tie positioned just under the bucket's lip. The tie is the same type that can bind large bundles of wire, and Home Depot has them (part no. 728494104805). Pull the screen taut as you tighten the tie, so that the assembly resembles a drum. Alternatively, you can secure the screen with a large rubber band. Cut off the excess screen, leaving about a half-inch of fabric below the tie for future adjustments.

Finally, Hegerberg removes the bucket's handle and slips a large rubber band over it. After reattaching the handle, he connects the band to the finder scope to relieve some of the stress on the focusing assembly [see illustration above]. Depending on the size of your bucket and scope, you might also need to add a counterweight to the telescope tube.

To get a clear image of the sun, you'll need a good eyepiece and a filter that screws into it. Hegerberg recommends Plössl eyepieces because they deliver the sharpest and best color-corrected images, but Huygenian eyepieces contain no cemented elements and so may better survive long-term exposure to the sun's heat. You'll need focal lengths between 17 and 25 millimeters depending on the size of your telescope. If you happen to own a Schmidt-Cassegrain telescope, try a 20-millimeter eyepiece for a four-inch instrument and a 25-millimeter eyepiece for an eight-incher. Sirius Plössl eyepieces retail for about $50 from Orion. If your telescope's aperture is larger than four inches, you must attenuate the light using a piece of cardboard with a four-inch hole in it. Attach this cardboard to the front of your scope. Otherwise, your instrument could overheat.

For the filter, Hegerberg recommends #21 (orange), #11 (yellow green) and #12 (yellow), any of which Orion sells for about $15. But keep in mind that these filters were never intended for direct solar viewing. Just as you would never press your eye over the lens of a movie projector, so you should never look directly into the eyepiece--even with one of these filters. Doing so could permanently damage your vision. The projection screen on the Sun of a Gun diffuses the light so that it is safe to look at.

Because the finder scope can focus sunlight enough to cause burns, always cover it before using the Sun of a Gun. Of course, never look through the finder scope at the sun. To align the telescope with the sun, first adjust its position so that it casts the smallest possible shadow. Then use the focus to sharpen the image on the screen.

Armed with this powerful tool, you'll be ready to explore our home star on any clear day. You, too, may enjoy observing the life cycle of sunspots, recording the ratio of the umbra to penumbra area or mapping their size over time.

For more information about this and other projects, check out the Society for Amateur Scientists's Web page. You may also write the society at 5600, Post Road, #114-341, East Greenwich, RI 02818, or call 1-401-823-7800.

Image: Daniels and Daniels

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.