Astronauts Neil Armstrong and Buzz Aldrin stepped into history 238,000 miles from here, on July 20, 1969, at a desolate spot called the Sea of Tranquillity. It's been 30 years since humans first walked on the moon.

Armstrong, Aldrin and Michael Collins left Pad A at the Kennedy Space Center, Fla., aboard Apollo 11 on July 16. After a four-day journey, they reached the moon's vicinity.

Collins stayed in the command module, Columbia, orbiting the moon while Armstrong and Aldrin boarded the lunar module, Eagle, and prepared to descend to the moon's surface. At 4:18 p.m. EDT, the Eagle landed. About six hours later Armstrong came out of the module, climbed down the ladder and weightlessly strode onto a place where prior generations only dreamed of going.

Fifteen minutes later, Aldrin joined his colleague on the dusty surface. But before he did, he said, "Now, I want to partially close the hatch, making sure not to lock it on my way out." Armstrong replied: "A good thought."

The astronauts returned safely to Earth four days later. Recount that glorious time with some special events:

July 10 -- "Exploring Space: Apollo 11 Family Night," at the National Air and Space Museum, from 6:45 p.m. to 11 p.m. A play about a young astronomer's dream of going to the moon, "Apollo to the Moon," will be performed. You'll participate in hands-on activities, see the Apollo 11 command module Columbia, and hear plans about the International Space Station. Recommended for families with children ages 7-12. Registration deadline: Today. Fees: $20 for adults, $10 for children. Information, 202-357-2700.

July 18 -- Goddard Space Flight Center's Model Rocket Contest, 10 a.m. to 4 p.m. Trophies go to the winners of the altitude and parachute spot landing events. At the Goddard Visitor Center in Greenbelt. Rain date: July 25. Information, 301-286-8981.

July 20 -- "Discover the Moon Activities," at the National Air and Space Museum, 10 a.m. to 4 p.m. Participate in the Lunar Touchables demonstration, take a lunar quiz and meet Andy Chaikin, author of "A Man on the Moon."

July 20 -- "The Dynamic Moon: What We've Learned from the Apollo Missions," a talk presented by the AstroTerps, the undergraduate astronomy club, at the University of Maryland astronomy department's open house. Sky viewing after the lecture. At the university observatory, on Metzerott Road across from the system administration building. 9 p.m. Information, 301-405-3001 during business hours [www.astro].

While we celebrate the moon this month, the planets and stars put on their own spectacular show. Mars is just west of south in the evening sky as dusk falls. As the summer sky darkens, you'll see the red planet noticeably close to a famous summer star Spica in the constellation Virgo. When facing south, Spica is to the right (west) of Mars. In clear skies, at dusk, you should be able to find Mars.

If you speed on from Spica and look higher, you'll see the star Arcturus in the tail of the constellation Bootes.

Meanwhile, Venus presents a dazzling sight in the western sky. At sunset, you'll be able to see the first glimmer of this bright planet. It is now located in the constellation Leo, nestled comfortably next to the star Regulus. (Regulus is the "period" in the backward question-mark shape in Leo.) Watch a young moon sneak up on Venus on July 15.

For those with a clear view of the horizon, see the fleet Mercury this evening just above west-northwestern horizon.

Jupiter ascends the eastern sky in the early morning hours, followed closely by Saturn. Now in the constellation Pisces, Jupiter rises at about 1:30 a.m. Jupiter and Saturn are high in the southeast just before dawn. In two weeks, both planets will rise about an hour earlier, and by the end of the month, a bright Jupiter will be rising shortly after midnight, and Saturn follows about 45 minutes later.

Down-to-Earth Events

July 10 -- Explore this summer's heavenly objects with the National Capital Astronomers and the National Park Service at Military and Glover roads NW, near the Rock Creek Nature Center. Telescopes will be set up. 9 p.m. Information, 202-426-6829.

July 25 -- Scheduled to launch in the fall of 2000, the Microwave Anistropy Probe satellite will measure the temperature differences in the cosmic background radiation. Learn all about it in a talk by NASA scientist Gary Hinshaw at the Goddard Space Flight Center's Visitor Center in Greenbelt. 1 p.m. Information, 301-286-8981.

July 31 -- What causes the seasons? Astronomers using a planetarium projector provide the answer in a lecture, "Why the Seasons?" 6 p.m., Einstein Planetarium, National Air and Space Museum.