TUSCALOOSA, Ala. (AP) — Tuscaloosa will experience a partial solar eclipse when the moon passes between the sun and the Earth in August, and astronomers at the University of Alabama are preparing to help people view the astral phenomenon safely.

Dean Townsley, an associate professor in UA's Department of Physics and Astronomy, said the eclipse is expected to be visible in all 48 of the continental United States on Aug. 21.

Most astronomers on campus plan to head to points north on that day, settling somewhere inside the 70-mile swath where the sun will be obscured entirely and viewers on the ground can experience a total solar eclipse. Townsley, though, will be on the Quad in front of Gallalee Hall equipped with a number of tools for safely observing the event.

"I run simulations and work with stellar physics, so I'm more about calculations than observations," Townsley said. "That may make me a little less sky-oriented than others in the department, so I'll still be here."

Townsley plans to set up a table with a telescope, a projection screen and 100 filtered viewing devices so anyone can walk up and experience the partial eclipse without damaging their eyesight.

"I think people are so interested in eclipses because they don't happen very often, it's only every decade or so that there's an eclipse people can see," Townsley said. "It's really interesting to us to observe something in the sky change, to become different while we're standing there and it's also dramatic -- if you're in totality, the sun just goes out."

William Keel, another UA astronomer, said 90 percent of the sun will be obscured during the height of the eclipse in Tuscaloosa. He said an eclipse that "deep" was last visible here in 1991 and the next won't occur until 2024.

The real show, though, is predicted in August 2045, when astronomers expect Tuscaloosa, Montgomery, Dothan and all points in between will experience a total solar eclipse.

"It's an astonishing thing that we can tell where the moon is going to be to the fraction of a second, but we're far enough from the sun and from black holes that even Newton's understanding of gravity made the study of the motion of planets a really exact science," Keel said. "Planets and moons move through space to with extraordinary high accuracy, and when you're calculating that motion, nothing but gravity matters."

The partial eclipse next month should begin a few minutes after noon and reach the moment of greatest obscurity around 1:30. Keel said observers in Tuscaloosa and elsewhere across the country will be "completely at the mercy of the weather," but said he was rooting for a clear day.

"For anybody's who has ever experienced a total solar eclipse, it's an emotional experience on top of what you see visually," Keel said. "It's something else."

The best way to view the partial solar eclipse over Alabama that day are pinhole projections, solar filters and projections from telescopes or binoculars, he said.

. Pinhole projection: In this method, sunlight passing through a small hole makes an image of the sun on whatever surface is used as a screen. The image of the sun gets larger the further the screen is from the hole, and only small holes will work, Keel said. A puncture in cardboard or aluminum foil works well, but any material works, and even gaps in tree leaves can project the eclipse onto the ground, he said.

. Solar filters: Solar filters are thin films in a cardboard or plastic mount. Only special-purpose solar filters, such as eclipse glasses or handheld solar viewers, are sufficient to look at the sun. Several vendors can provide safe solar filters, Keel said.

. Projections through lenses: Most telescopes and binoculars can focus enough to project a sharp image of the sun onto a sheet behind the eyepiece. Telescopes with eyepieces at a 90-degree angle from the tube offer easy ways to shade the image for clearer views, Keel said. Those choosing this method need to be careful to keep anyone from looking directly through the eyepiece to avoid severe damage to the eye.

___

Information from: The Tuscaloosa News, http://www.tuscaloosanews.com