IF YOU'RE not already packed for Hawaii, Baja California or Central America, you're probably going to have to settle for a partial eclipse when the moon passes across the sun's face Thursday afternoon.
Assuming skies are clear, the best you're going to be able to do in Baltimore or Washington will be to watch as a maximum of 7 percent of the sun's disk is nipped by the new moon.
The partial eclipse will begin here at 2:57 p.m. and obscure part of the sun's lower right quadrant.
The event will reach its maximum at 3:34 p.m., and it will all be over in Baltimore at 4:09 p.m.
Marylanders who aren't looking for it probably won't realize anything's happened. The sun's light will not be significantly diminished here.
For those who are looking, eye care specialists warn that no one should attempt to watch the eclipse directly. The sun's rays can scar the retina in seconds.
"The damage is generally irreversible and can conceivably cause central blindness," or a loss of vision at the point of focus, said Dr. Earle L. Hunter, executive director of the American Optometric Association, in St. Louis.
It's painless, Hunter said, and "sometimes you won't notice it for 10 to 24 hours. Then you start saying, 'Gee, where did that person's face go?' But there are no live cells there to receive an image."
"Parents . . . have really got to convince their kids not to take a look," he said.
After a total eclipse in March 1970, at least 245 people in the U.S. suffered eye damage; half of them never recovered their full vision, according to Sky and Telescope magazine.
Viewing the eclipse through smoked glass, photographic film or even most welders glasses is also risky, since they can pass damaging amounts of ultraviolet or infrared radiation to the retinas. Trying to watch directly through binoculars or a telescope, which magnify the sun's light, is even more dangerous.
Instead, doctors recommend viewing the eclipse indirectly, using one of several easy-to-make devices that project an image of the sun onto a piece of paper.
For the best and safest view of a slight partial eclipse like this week's, experienced eclipse-watchers recommend one of the following methods:
* An eclipse mirror: Punch a quarter-inch hole in a piece of paper and tape the paper over a small, high-quality mirror. Place the mirror on a windowsill in such a way that sunlight reflected from the mirror projects onto a far wall inside the room. The spot of light on the wall is an image of the sun's face, and you can safely watch the eclipse progress.
* An eclipse box, or "sunscope": Follow the directions in the graphic on page C1, or buy a ready-made eclipse box.
"I made one once for my kids, and it works like a charm," Hunter said. "It makes it safe and interesting."
Eclipse box kits are available at The Nature Company store at Harborplace in Baltimore. They cost $9.95 each and include instructions and general information about eclipses.
The July edition of Sky and Telescope magazine ($2.95 at the newsstand) contains comprehensive information on this and future eclipses.
One of the best new books on eclipses for the general reader is "Eclipse," by Bryan Brewer, also available at The Nature Company (95 pages, $14.95). It is filled with photographs, illustrations, diagrams and text on the history, mythology and science of eclipses.
Brewer's book also includes a comprehensive list of future total solar eclipses around the world through the year 2035, and a map showing where each will be visible.