The autumnal equinox breezes in this month

Published September 3, 2005

The autumnal equinox occurs at 6:23 p.m. Sept. 22, marking the start of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. On this day, there will be equal amounts of daylight and darkness.

If you look low to the west-southwest at twilight, you'll see a spectacular grouping of Venus, Jupiter and the star Spica. The two planets were closest together Sept. 1 (about a degree apart); Venus is the brighter. Venus will remain at the same height above the horizon, while Jupiter moves closer to the glare of the sun and becomes lost to view toward the end of the month. Notice Spica, which moves ever closer to Venus until they reach their closest Monday through Wednesday. A thin crescent moon joins the trio on Tuesday and Wednesday.

Mars rises in the east around 10:30 p.m. at the start of the month and a little earlier each evening. Before dawn, Mars will be highest in the south-southwest. The planet will double its brightness as the Earth moves closer to it, and by the end of the month it will be almost as bright as Jupiter. Since Mars is only some 4,000 miles in diameter, it is of great interest as the telescope shows it becoming larger; the planet reaches maximum size and brightness on the evening of Oct. 29-30. This will be the best it gets for Mars fans until 2018.

Also notice that Mars is to the lower right of the moon on the evening of Sept. 21.

Before dawn, look toward the east to locate Saturn, which is nicely placed to the right of the crescent moon on the morning of Sept. 28.

In the morning twilight during the first week of September, you may find Mercury very low to the east-northeast horizon. The planet closest to the sun will be next to the star Regulus on Sunday.

At the planetariums

The Science Center of Pinellas County (7701 22nd Ave. N, St. Petersburg): The Science Center is offering planetarium shows on Saturdays at 11:30 a.m. and 2:30 p.m. and a laser light show on Saturdays at 1:30 p.m. A Super Saturday that starts at 10 a.m. on Sept. 10 features optical illusions, glowing minerals and much more.

Learn how to build a telescope at the ongoing classes Saturdays from noon to 4 p.m. in the optical laboratory in the annex building behind the main building. The St. Petersburg Astronomy Club meets at the Science Center at 8 p.m. Sept. 23. Visit its Web site at www.tampabayastronomy.com

For more information, call 727 384-0027 or visit www.sciencecenterofpinellas.com

St. Petersburg College (Fifth Avenue and 69th St. N, St. Petersburg): The college planetarium at the St. Petersburg campus will offer free planetarium shows at 7 and 8:15 p.m. on Friday nights. When the skies are clear, telescopes will be set up after the shows. Call (727) 341-4320 for details.

Gulfport: Telescopes will be set up Sept. 17 at dusk on the corner of Beach Boulevard and 31st Avenue S for astronomical viewing, but only if the skies are clear.

St. Pete Beach: Telescopes will be set up at dusk today for viewing on Corey Avenue in front of the Beach Memorial Funeral Home.

Bishop Planetarium (201 10th St. W, Bradenton): The Bradenton planetarium has undergone major renovation and is now showing "Passport to the Universe" for adults and "The Secret of the Cardboard Rocket" for the younger set.

Sonic Vision is an animated digital alternate music show. For more detail on the largest planetarium in the area, call 941 746-4131 or visit www.southfloridamuseum.org

Museum of Science and Industry (4801 E Fowler Ave., Tampa): The planetarium is showing "More Than Meets the Eye," which compares views of celestial objects by naked eye, binoculars and telescopes. Also, on weekends the "Tonight Show Live" explains what is visible in the current night sky.

The IMAX Dome Theater presents Top Speed, about super-fast humans pushing the envelope, and The Human Body.

The astronomy club MARS offers free telescope viewing at dusk Sept. 10, weather permitting. Call (813) 987-6100 or visit www.mosi.org for more events.

Sky calendar

TODAY-SUN.: Look low to the west-southwest to find Venus, Jupiter and the star Spica in a horizontal straight line.

SUN.: With the coming of dawn, look low to the east-northeast to find Mercury (on the left) next to the star Regulus.

TUE.-WED.: Low in the west-southwest, Venus, Jupiter and Spica (in order of brightness) are joined by the crescent moon.

SEPT. 10: Super Saturday at the Science Center of Pinellas County. SkyWatch at MOSI, where telescopes are set up for free viewing at dusk, under clear skies only. The red star Antares is to the right of the moon in the south-southwest after dusk.

SEPT. 11: First-quarter moon.

SEPT. 16: Moon is closest (perigee) to the Earth at 223,945 miles.

SEPT. 17: Full moon rises about the time the sun sets. Mercury in superior conjunction - on the other side of the sun. Telescopes set up in Gulfport at dark.

SEPT. 21: Mars to the lower right of the moon in the predawn hours. Look to the east-northeast.

SEPT. 22: Autumnal equinox is at 6:23 p.m. Mars to the lower right of the moon before sunrise.

SEPT. 23: St. Petersburg Astronomy Club meets at 8 p.m. at the Science Center of Pinellas County.

SEPT. 25: Last-quarter moon.

SEPT. 28: Look east to locate Saturn to the right of the crescent moon before the light of dawn. Moon is at an apogee (greatest distance) of 251,846 miles.

SEPT. 30: Regulus is to the upper right of the crescent moon in the east before sunrise.

- Daryl L. Schrader is an astronomy and mathematics professor at St. Petersburg College and teaches astronomy at the University of South Florida.