PORTLAND — Edward Gleason’s job won’t allow him to head south to see the total effect of what is expected to be the year’s most-viewed astronomical event.

But the University of Southern Maine astronomer, who manages its Southworth Planetarium, said the partial solar eclipse on Monday, Aug. 21 will offer plenty to see in the Portland area.

“Eye protection will be necessary throughout the entire event,” he cautioned Monday, for anyone who plans to watch during the 2 1/2 hours the moon will move through the path of the sun.

The moon will begin to move at 1:29 p.m., Gleason said, and the eclipse will cover nearly 60 percent of the sun over southern Maine for about 2 1/2 minutes beginning at 2:45 p.m.

By 4 p.m., the eclipse will be over. Another one won’t be seen locally until April 2024.

For total darkness, head south or west, where a swath from Oregon to South Carolina will go completely dark, Gleason said. Locally, head to Monument Square, where the Portland Public Library is handing out solar eclipse glasses for adults beginning at 1:30 p.m.

The glasses look like the 3-D kind first popularized at the movies 60 years ago, but they are tinted to make viewing the partial eclipse safe.

Gleason said human eyes cannot endure the bright stages before and after a total eclipse, or at any stage of a partial eclipse.

“The eyes have a protective reflex, it hurts too much,” he said of looking at the sun under normal conditions.

The eclipse can be viewed indirectly as well. One way is poking a hole in a piece of cardboard, then holding it over another piece while pointing the pinhole at the sun.

Gleason recommended lining a box with aluminum foil, making a pinhole, then attaching paper opposite the hole to watch the stages.

Preliminary weather reports call for sunny weather Aug. 21, and Gleason offered one last warning for watching the solar show.

“You want to be sure the eclipse shades block out the vast majority of the radiation,” he said. “If you are not sure, do not use them at all.”

David Harry can be reached at 781-3661 ext. 110 or dharry@theforecaster.net. Follow him on Twitter: @DavidHarry8.

A map showing the total solar eclipse’s “totality path,” the region where observers will be able to see a total solar eclipse on Aug. 21. Southern Maine sky watchers will see a partial solar eclipse.