Special to CosmicTribune.com, September 15, 2024

Excerpts from weekly Sky&Telescope report.

MONDAY, SEPTEMBER 16

■ The two brightest stars of September evenings are Vega high overhead and Arcturus in the west, both magnitude 0.

■ Saturn this evening glows about 5° to the left of the nearly full Moon. Watch the Moon close in on it as the hours pass.

Then, for the western U.S. and parts of western Canada, the Moon occults Saturn. The planet slips behind the Moon’s extremely narrow dark limb. Saturn emerges from behind the bright limb up to an hour or more later.

TUESDAY, SEPTEMBER 17

■ Full Moon (exact at 10:34 p.m. EDT). A slight partial eclipse of the Moon occurs this evening for the Americas. We’ll see the Moon’s celestial north-northeast edge slightly dented by the umbra of Earth’s shadow from 10:12 to 11:17 p.m. EDT (7:12 to 8:17 p.m. PDT; 2:12 to 3:17 Sept. 18 UT). At maximum eclipse (10:44 p.m. EDT), the shadow will intrude a mere 9% of the way across the Moon’s disk. It will just brush the northern edge of the crater Plato, the dark, mountain-rimmed walled plain just north of Mare Imbrium.

WEDNESDAY, SEPTEMBER 18

■ The closing days of summer (the equinox comes in four days) always find the Sagittarius Teapot moving west of south during evening and tipping increasingly far over to the right, as if pouring out summer’s last tea.

THURSDAY, SEPTEMBER 19

■ Arcturus shines in the west these evenings after twilight fades out. Capella, equally bright, is barely rising in the north-northeast (depending on your latitude; the farther north you are the higher it will be.) They’re both magnitude 0.

Later in the evening, around 9 or 10 p.m. depending on your location, Arcturus and Capella shine at the same height in their respective compass directions.

FRIDAY, SEPTEMBER 20

■ Are you spotting Venus yet low in the afterglow of sunset? Is Spica already gone for you even with optical aid? See the scene below.

Venus is becoming a little more easily visible low in the sunset afterglow, while Spica is becoming ever more challenging, even with binoculars, as it moves down and away. This evening they’re 4° apart. Say goodbye to Spica until next spring.

SATURDAY, SEPTEMBER 21

■ The waning gibbous Moon rises in mid-evening: around 9 p.m. daylight saving time. Once it’s well up, notice the Pleiades just a few degrees to its lower left. The Moon creeps closer to them all through the night. It skims the southern edge of the cluster around dawn, depending on your location.

SUNDAY, SEPTEMBER 22

■ Earth crosses the September equinox point in its orbit at 8:44 a.m. EDT (12:44 UT). This is when the Sun crosses Earth’s equator on its six-month apparent journey south. Fall officially begins in the Northern Hemisphere, spring in the Southern Hemisphere.

Coincidentally, as if to mark this transition every year, Deneb is gradually taking over from brighter Vega as the zenith star after nightfall (for skywatchers at mid-northern latitudes).

This Week’s Planet Roundup

Mercury (magnitude –1.1) sinks lower in the dawn day by day. Early in the week, try for it very low due east about 30 minutes before sunrise. Binoculars help.

Venus, magnitude –3.9, is still very low in bright twilight. Starting 30 minutes after sunset, look for it low above the west-southwest horizon. Venus is getting very slightly higher and brighter week by week.

Spica, magnitude +1.0 (meaning 1/80 as bright), has been closing in on Venus. On Friday September 13th it’s 6° to Venus’s left. They pass each other on Monday the 17th, with Spica 2½° to Venus’s lower left. After that Spica continues its downward journey.

Mars and Jupiter (magnitudes +0.6 and –2.4, respectively) continue pulling apart from each other in the early-morning sky. Watch for bright Jupiter to rise in the east-northeast around 11 p.m. daylight-saving time. Mars, much fainter, rises more than an hour later to Jupiter’s lower left.

Saturn (magnitude +0.7, in Aquarius) is a few days past opposition. Look for it glowing fairly low in the east-southeast as the stars come out. It’s lower right of the Great Square of Pegasus, which is balancing on one corner. The Square’s upper-right edge points diagonally to Saturn, two fists at arm’s length away.

Saturn climbs higher through the evening. It shines highest in south by midnight.

  Sept. 16-22: Saturn rising as summer ends, The Sky