Sunday evening, we face the opposition.

When Saturn reaches astronomical opposition, we’ll be treated to some marvelous views of the ringed and gaseous planet as it stands opposite the sun, from Earth’s perspective. In other words, when Saturn ascends the eastern sky at dusk, the sun will be setting in the west.

Think about this concept: When the moon is full from Earth’s perspective, the moon is opposite the sun. On the evening of a full moon, the lunar orb rises in the east at dusk while the sun sets in the west. It’s the same for Saturn and the sun.

With clear skies at night, Saturn loiters in the constellation Virgo at sundown, near the star Spica. This planet becomes a beacon to find at zero magnitude, which is bright enough to see from urban, light-polluted locations. Through April, it generally remains visible all night long.

Saturn gets a cosmic weekend guest, as the waxing moon approaches it April 16. Find the official full moon April 17, when it becomes this celestial body’s turn to sit opposite the sun.

Like cowboys entering town at dawn, the foursome of Mercury, Venus, Mars and Jupiter find their way back to the eastern sky in late April. About 6 a.m. April 22, Venus ascends first, followed by Mercury, Mars and Jupiter — all ahead of the sun and all trying to shed the sun’s glare.

By April 30, before dawn, the waning, skinny crescent moon scoots near Venus (very bright, at negative third magnitude), just above the eastern horizon. Find fleet Mercury — albeit dimmer and a little lower than Venus — at zero magnitude. The two lagging planets, Mars and Jupiter, have moved into a huddle. They conjunct May 1.

Down-to-Earth events
l  April 4: “Stars Tonight” for April at the David M. Brown Planetarium, 1426 N. Quincy St., Arlington, adjacent to Washington-Lee High School. Hosted by Jonathan Harmon, director. $3 for adults, $2 for seniors and children. 7:30 p.m. Information, 703-228-6070. ­saveplanetarium.­org.

l  April 5: Astronomer Alex Moiseev discusses “High Energy Cosmic Ray Electrons: Messengers from Nearby Cosmic Ray Sources or Dark Matter?” at the open house at the University of Maryland Observatory, College Park. Heavenly views with a telescope afterward, weather permitting. 8 p.m. 301-405-6555. ­astro.­umd.edu/openhouse.

l  April 7: See images of Martian avalanches made from frost, dust and ice in “Mars: A Dynamic World,” a lecture by Alfred S. McEwen, a professor at the University of Arizona and the principal investigator for the HiRISE camera on the Mars Reconnaissance Orbiter. Lockheed Martin Imax Theater, National Air and Space Museum, the Mall. Meet the lecturer at 7:30 p.m. The lecture starts at 8. At 9, telescope viewing outside the museum. nasm.si.edu.

l  April 9: Jessica Rosenberg, George Mason University astronomer, examines “Gas and Stars in the Local Universe: What Normal Matter Can Teach Us About the Formation and Evolution of Galaxies,” in a lecture at the National Capital Astronomers meeting, University of Maryland Observatory, College Park. 7:30 p.m. ­capitalastronomers.org.

l  April 10: Astrophysicist Kirk Borne of George Mason University talks on “The Large Synoptic Survey Telescope: Mapping the Dynamic Universe,” at the regular meeting of the Northern Virginia Astronomy Club. 7 p.m. Enterprise Hall, Room 80, GMU, Fairfax. novac.com.

l  April 16: Discover cosmic distances and time, and how the universe is pixelated, in “Time-Space Invariance and Quantum Gravity: Or how c, G, and h create the fabric of Reality!” at the Montgomery College planetarium, Takoma Park. 7 p.m. montgomery ­­­college.edu/­Departments/planet.

l  April 20: Dennis Bodewits on “Cometary X-rays” at an open house at the University of Maryland Observatory, College Park. Telescope viewing afterward, weather permitting. 8 p.m. 301-405-6555. www.astro.umd.edu/openhouse.

Blaine Friedlander can be reached at PostSkyWatch@gmail.comPostSkyWatch@gmail.com.