For the past nine months, Maine Skies has been looking at monuments erected by the ancients to track significant astronomical events to which they attached religious connotations. None of these edifices has inspired more awe down through the ages than Stonehenge. It is fitting to end this topic with a three-part series on Stonehenge that will cover when it was built, its general structure, and its likely purpose.

Much of the material will come from “Stonehenge Decoded,” by archaeoastronomer Gerald S. Hawkins, whom I was privileged to know when he was on staff at Boston University.

Stonehenge was begun around 3000 B.C. by a Neolithic culture, the Windmill people, who used tools of stone and bone to begin digging huge circular ditches. They were followed 1,000 years later by the Beaker people, a Bronze Age culture named for their distinctive pottery burial drinking cups. They were responsible for setting up the huge stones we all associate with pictures of Stonehenge today. Last came the Wessex people around 1500 B.C., who built the inner rings and began the final structures that apparently never got completely finished.

Think of it. Three separate cultures, having no written language and in a constant battle for sheer survival, spent somewhere between one to two millennia building this massive stone structure. What could have possessed them to do it? Next month, a look at the physical structure of Stonehenge.

Focus on the planets

Venus may be the brightest of the planets, but October belongs to Mars as, over the next month and a half, it shines brighter and appears larger than it will again for 13 years.

Mercury is very low in the west, to the lower left of Jupiter, at sunset and will not climb into any position of prominence during the month.

Venus blazes low in the southwest at dusk. It will climb slowly up the horizon during October for a splendid showing in late November.

Mars continues to get larger and grow brighter throughout October. Look for the Red Planet to rise about 8:30 p.m. as the month opens and to be visible in the east at twilight as it draws to a close. Mars will be a large, orange Halloween pumpkin on All Saints Eve.

Jupiter is low in the west at sunset during the opening days of October. Look for the giant planet as it shines brightly to the lower right of Venus.

Saturn rises in the early morning hours and is high in the southeast at dawn. Look for the Beehive Cluster positioned to the upper right of Saturn.

Uranus is moderately high in the southeast as darkness falls, where its blue-green disk is a fairly easy target with binoculars as it nestles among the stars of Aquarius.

Neptune is high in the south during the early evening hours where its bluish-gray disk is visible with good binoculars or small telescope among the stars of Capricornus.

Pluto is a lost cause in October.

October events

1 Sunrise, 6:33 a.m.; sunset, 6:17 p.m.

3 New moon, 6:27 a.m.

4 The Soviets launched Sputnik 1 on this date in 1957, propelling the United States into the space race.

6 Venus sparkles above the thin crescent moon on the southwest horizon shortly after sunset.

7 The bright reddish star at the upper tip of the waxing crescent moon tonight is Antares.

8 The Draconid meteor shower peaks tonight. However, it is expected that very few of the slow-moving meteors will be visible.

10 Moon in first quarter, 3:01 p.m.

14 The moon is at perigee, or closest approach to Earth, today.

17 Full moon, 8:13 a.m. As the next full moon after the Harvest Moon, this is the Hunter’s Moon.

19 Mars shines to the right of the moon as they rise together shortly after dark.

21 The Orionid meteor shower peaks tonight. Formed by debris from Halley’s comet, the Orionids normally produce 20-25 meteors per hour, but its nearness to the full moon will likely lead to a disappointing shower this year.

23 The sun enters the astrological sign of Scorpio but, astronomically, is still in Virgo.

25 Moon in last quarter, 9:17 p.m. Saturn shines to the lower right of the moon just before dawn. The two bright stars high above are the twins Castor and Pollux.

26 The moon is at apogee, or greatest distance from Earth, today.

30 Daylight-saving time ends at 2 a.m. tonight. Don’t forget to set your clocks back one hour. The sun enters Libra on the ecliptic. Mars is closest to Earth tonight at a mere 43 million miles.

31 Halloween or the eve of All Saint’s Day. This is one of the cross-quarter days marking the midpoint between the autumn equinox and winter solstice. Sunrise, 6:12 a.m.; sunset, 4:26 p.m.