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Tue12102019

Last updateTue, 18 Sep 2018 1pm

Robert Victor

Follow the moon each day at dusk or dawn—and within one cycle, it will introduce you to as many as all five naked-eye planets, and the five bright stars of first magnitude within the belt of zodiac constellations.

The new moon occurs on Friday, Oct. 4. Two days later, on Sunday evening, Oct. 6, about 20 minutes after sunset, a thin sliver of a young lunar crescent will appear very low in the west-southwest, 20 degrees to the lower right of the bright “evening star,” Venus.

Valley residents would need to seek out a place with an unobstructed sight line in that direction, since the moon will be less than 6 degrees up at 7 p.m., within a half-hour after sunset. (In other words, if you’re in downtown Palm Springs or elsewhere near the mountains, you’re out of luck!) But the view through binoculars is worthwhile: Flanking the moon will be Saturn, 3 degrees to the upper right, and Mercury, 2 degrees to moon’s lower left—all within a 5-degree field!

Mercury and Saturn are in the process of departing the evening sky, but Venus remains visible at dusk until early January.

As the moon withdraws farther from the sun nightly, the crescent thickens, and appears within 8 degrees of Venus the next two evenings—to the planet’s lower right on Monday, Oct. 7, and to its upper left on Tuesday, Oct. 8.

On Saturday, Oct. 12, the local Astronomical Society of the Desert will resume hosting its free monthly star parties at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, 4 miles south of Highway 111 in Palm Desert). For more info and a map, visit the society’s website, at www.astrorx.org. Early that evening, and until Sunday, Oct. 20, the famous red supergiant star Antares will appear within 5 degrees of Venus. On Wednesday, Oct. 16, they’ll be as close as 1.5 degrees, with Venus passing above the distant star.

High in the east these mornings, another striking pair, of reddish Mars and blue-white Regulus, takes place. From Oct. 7-23, they’ll appear within 5 degrees, and within 1 degree on Tuesday, Oct. 15.

Continue watching the moon in the evening sky until it reaches full on Friday, Oct. 18, when it rises around sunset, and for a few nights beyond, as it rises later each evening.

Look around 6 a.m. (about an hour before sunrise) for these events: On Oct. 22, the moon is near Aldebaran, eye of Taurus; on Oct. 25 and 26, the moon is near Jupiter (the brightest “morning star”) and the Gemini twins, Pollux and Castor. On Oct. 29, find the moon near Regulus and Mars, forming a nearly equilateral triangle 7 to 8 degrees on a side. On Nov. 1, look for Spica 9 degrees to the lower left of the crescent moon. On Nov. 2, about 45 minutes before sunrise, watch for the last thin old crescent moon rising 4 to 5 degrees to the lower left of Spica.

Beginning in mid-November, four bright planets will span the morning sky, and the long-awaited Comet ISON may perform. Check the Sky Calendar website for updates.

More here next month!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.

Courtesy www.pa.msu.edu/abrams/skycalendar

The Coachella Valley is a great place for inspiring views of the night sky—and among the visually impressive events is the pairing of Venus and the crescent moon.

While Venus is still visible in the evening sky for a few more months, Venus-Moon pairings will occur at dusk on Sept. 8, Oct. 7 and 8, Nov. 6, Dec. 5, and Jan. 1 and 2. Of these, the pairing this month, on Sunday, Sept. 8, will be the closest, and the moon will even help the observer spot Venus as they move together across the daytime sky.

From Southern California, the moon and Venus appear closest, in the southeast sky shortly after noon, with Venus only 0.6 degrees, or just more than the moon’s width, from the northern cusp or point of the crescent. When the moon and Venus are highest—due south, nearly halfway from horizon to overhead around 3:15 p.m.—they’re more than a degree apart. By sunset, Venus will appear more than 2 degrees to the right of the moon.

As twilight deepens, after 45 minutes, look for Spica within 4 degrees to the lower right of Venus—binoculars will help pick it out of the bright twilight—and Saturn some 11 degrees to the upper left of Venus, and 9 degrees to the upper left of the crescent moon.

But don’t wait until Sunday, Sept. 8, to begin watching! During Labor Day week, the star Spica appears quite close to Venus, only 1.6 degrees to the lower left of the brilliant planet on Thursday evening, Sept. 5. Venus now moves about a degree daily against the background, so it will be easy to notice changes in their arrangement from one night to the next. A thin crescent moon can be easily spotted on Saturday evening, Sept. 7, if you look early enough—say, half an hour after sunset. You may want to keep a log of your sky-watching sessions, with notes and drawings of what you see.

On Sunday evening, Sept. 8, as the moon and Venus sink into the west-southwest—because of the Earth’s rotation—the moon creeps slowly to the upper left of Venus, owing to the moon’s revolution around the Earth. Check again after sunset on Monday evening, Sept. 9, to see how far the moon has progressed in 24 hours. On that evening, Saturn appears about 6 degrees to the right of the crescent moon. By Wednesday evening, Sept. 11, the red supergiant star Antares appears within 7 degrees below the moon, now nearly half-full. On Thursday the 12th, the moon appears just more than half full, having passed first quarter phase, 90 degrees east of the sun, earlier that day. The moon is full overnight Sept. 18-19, rising not long before sunset on the 18th.

For the next several evenings, the waning “Harvest Moon” comes up not much later each night, still rising before 9 p.m. on Sept. 22.

You can follow the waning moon in the morning sky daily an hour before sunrise from Sept. 19 through Oct. 3, watching it pass, in turn, Aldebaran, Betelgeuse, Jupiter, Pollux and Procyon, Mars, and Regulus. (See September’s morning twilight sky map below.)

Daytime Moonwatch: If you have children, take them outdoors daily Sept. 23-Oct. 2 to follow the moon as it changes from 82 percent full on Sept. 23, through 46 percent on Sept. 27 (just after passing last quarter phase, when it’s 90 degrees from the sun), to a thin 6 percent crescent on Oct. 2, just 28 degrees from the sun. The best time for this project is before students go off to school, or even while they are at school (suggest this moon-watch activity to their teacher), in playground time before classes begin, or as late as 9 a.m. This activity can be repeated during Oct. 21 through Nov. 1.

Whenever a planet passes near a star or another planet, the event will be great fun to track nightly for a week before and after the night they’re closest. Evening pairs coming soon include Venus-Spica on Sept. 5, Venus-Saturn 3.5 degrees apart on Sept. 17 and 18, and Venus-Antares 1.5 degrees apart on Oct. 16. Antares is the heart of Scorpius, the Scorpion. Our evening twilight chart for September (above) will help you pick out Venus, Saturn and the brightest stars as they appear about 40 minutes after sunset.

Now in the morning sky, bright Jupiter is a slow-moving planet, taking 12 years to make one circuit around the belt of zodiac constellation. During the 2013-2014 school year, note the changing shape of the triangle Jupiter makes with the Gemini twin stars of Pollux and Castor. During Labor Day week, these twin stars appear 11 to 12 degrees to the lower left of Jupiter, while Mars appears some 20 degrees more steeply lower left of Jupiter. On the weekend of Sept. 7-9, Mars passes through the Beehive Cluster of faint stars, an event best seen with binoculars. In a colorful, pretty pairing on the morning of Oct. 15, reddish Mars will pass within 1.0 degree of the blue-white 1.4-magnitude star Regulus, heart of Leo, the Lion.

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.

At dusk, watch Venus slowly close in on Spica and Saturn, until pairings occur in September.

Meanwhile, the best Milky Way viewing occurs this year on evenings through Aug. 9, and then again Aug. 26 through Sept. 7. Get to a dark site by nightfall, and enjoy!

Dark moonless predawn hours of Aug. 12 and 13 make this an excellent year for the annual Perseid meteor shower. And mid-August, dawn brings forth the greatest number of bright stars visible simultaneously.

Venus continues as the brilliant evening “star” low in evening twilight, while drifting from west to west-southwest as month progresses. Valley residents living closely east of mountains (such as near downtown Palm Springs) will want to seek out a location where the mountains don’t block the planet from view.

Venus will grace our evening sky until early January 2014. Until then, a waxing crescent moon passes Venus monthly, producing the most striking views at dusk on Friday, Aug. 9, and on Sunday, Sept. 8. Don’t miss these!

On our evening all-sky chart above, planets are plotted for each day when the sun has sunk to 9 degrees below the horizon, at “mid-twilight.” By then, two naked-eye planets and a half-dozen stars of first magnitude or brighter are easily seen. In mid-August in the Coachella Valley, mid-twilight occurs about 42 minutes after sunset.

Planet positions are represented by a separate dot for each date, with positions for each Thursday in August (1, 8, 15, 22, 29) represented by a larger dot and labeled. We find Saturn and Spica in the southwest to west-southwest sky this month, to the upper left of Venus. Rotate the chart until the portion of the horizon circle nearest to your target objects is below them, and you’ll see them depicted at the same orientation as they appear in the sky: On Aug. 1, Venus is in the west, with Saturn in the southwest 53 degrees to Venus’ upper left, while Spica is 12 degrees to the lower right of Saturn, and 41 degrees to the upper left of Venus. On Aug. 31, Venus is in the west-southwest, with Saturn 19 degrees to its upper left, while Spica is just 6 degrees to the upper left of Venus, and 14 degrees to the lower right of Saturn.

On the chart, stars’ daily positions are plotted not as individual dots, but instead by continuous tracks as the stars drift west (counter-clockwise around the North Star) over the course of the month, owing to the Earth’s revolution around the sun.

The brightest star in August’s evening sky is golden Arcturus, high in the west-southwest to west, to upper right of Saturn and Spica and forming a large triangle with them. When the sky darkens enough for the Big Dipper to become visible, you can “follow the arc (of the handle) to Arcturus and drive a spike to Spica.”

A close second to Arcturus in brilliance is blue-white Vega, very high in the east-northeast. Compare the contrasting colors of these two stars! To Vega’s lower left is Deneb, and to Vega’s lower right is Altair, completing the Summer Triangle. Face south to south-southwest to find reddish Antares, heart of the Scorpion.

From Aug. 8-21, the moon is above the horizon in evening mid-twilight. Follow it nightly as it waxes, or grows, from a thin crescent on Aug. 8, past first quarter (half full) by Aug. 14, to full on Aug. 20. The moon appears near Venus on Aug. 9, Spica on the 11th, Saturn on the 12th, and Antares on the 15th.

(I recommend the Abrams Planetarium Sky Calendar for its easy-to-follow illustrations of the changing positions of moon and planets against background stars. The current issues feature illustrations of the changing arrangements of Venus-Spica-Saturn at dusk and Jupiter-Mars-Mercury at dawn. Each month, an all-sky evening chart of the constellations is also provided. To subscribe, visit www.pa.msu.edu/abrams/SkyCalendar.)

Star Parties

The Astronomical Society of the Desert hosts free public sky-watching sessions at Sawmill Trailhead on Saturday evenings, Aug. 3, and Sept. 7. For more information and directions, visit www.astrorx.org and www.astrorx.org/sawmill%20Directions.htm.

August Evening Moonrise Watch

The full moon occurs on Tuesday, Aug. 20, at 6:45 p.m. in the Coachella Valley.

That evening, the moon rises nine degrees south of east at 7:05 p.m., about 22 minutes before sunset. Does the full moon at rising seem large? The moon at rising or setting always seems large (the “moon illusion”), even when it is at its most distant from Earth.

For those who enjoy watching or photographing the moon’s big reddened disk coming up over distant mountains, here are moonrise times for the Coachella Valley until a week after full. Times are when the moon’s disk would just start to appear over an ideal, flat horizon. In practice, our mountainous surroundings will delay risings and hasten settings by several minutes.

Tuesday, Aug. 20: 7:05 p.m.—9 degrees south of east (full)

Wednesday, Aug. 21: 7:44 p.m.—3 degrees south of east (98 percent)

Thursday, Aug. 22: 8:21 p.m.—3 degrees north of east (94percent)

Friday, Aug. 23: 8:57 p.m.—8 degrees north of east (88 percent)

Saturday, Aug. 24: 9:34 p.m.—13 degrees north of east (80 percent)

Sunday, Aug. 25: 10:12 p.m.—17 degrees north of east (71 percent)

Monday, Aug. 26: 10:53 p.m.—21 degrees north of east (61 percent)

Tuesday, Aug. 27: 11:35 p.m.—23 degrees north of east (51 percent)

August Predawn Riches!

Up to 13 objects of first magnitude or brighter, and a meteor shower, are all visible in the early morning hours! Our all-sky chart for morning mid-twilight, below, depicts the sky about 42 minutes before sunrise in the Coachella Valley.

Jupiter is the bright morning “star.” In mid-twilight, you’ll find it about 20 degrees up in east-northeast on Aug. 1, and climbing nearly halfway from the east horizon to overhead by month’s end. Mars, of magnitude 1.6 (and not quite qualifying as first magnitude), is to the lower left of Jupiter, within 5 degrees on Aug. 1, and widening to 18 degrees by Aug. 31. Mercury on Aug. 1 is within 8 degrees to the lower left of Mars and 12 degrees to the lower left of Jupiter, but drops into bright twilight around mid-month. To Jupiter’s upper left, find bright Capella, the “Mother Goat” star, in the northeast, getting higher as month progresses. To the upper right of Jupiter is reddish Aldebaran, eye of Taurus the Bull, with the compact Pleiades star cluster or Seven Sisters (not shown), 14 degrees higher. Below Taurus, find Betelgeuse and Rigel, shoulder and foot of Orion the Hunter (with his belt, a nearly vertical line of three stars midway between them, not plotted).

The Summer Triangle of Vega-Deneb-Altair is still visible in the west to west-northwest at dawn early in August, but only Deneb remains at month’s end.

From midnight through the predawn darkness hours of Monday and Tuesday, Aug. 12 and 13, watch the annual Perseid meteor shower rise to peak. With no moon present to spoil the view, this is a very good year!

After viewing the shower, follow Orion’s belt downward as dawn brightens to watch for the rising of Sirius, the “Dog Star,” in the east-southeast. Procyon will have already risen in the east; it completes the Winter Triangle with Sirius and Betelgeuse. Try to spot Sirius before you lose sight of Altair sinking in the west, and you’ll see both the winter and summer triangles simultaneously!

If you succeed, you can tally 11 stars and two planets of first magnitude or brighter. We’ve not yet mentioned Pollux, in the east-northeast to the lower left of Jupiter (with 1.6-magnitude Castor, the other Gemini Twin, not plotted, 4 1/2 degrees above Pollux), and Fomalhaut, mouth of the Southern Fish, very low in southwest.

The waning crescent moon in the morning sky appears near the Pleiades star cluster on and Aug. 27, Aldebaran on Aug. 1 and 28, Jupiter on Aug. 3 and 31, Mars on Aug. 4 and Sept. 2, and Mercury on Aug. 5.

Robert C. Victor was a staff astronomer at the Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

In July 2013, the brilliant evening “star” Venus gleams low in evening twilight, drifting from west-northwest to west as month progresses. Valley residents living near the mountains (in downtown Palm Springs, for example) will have to seek out a location where mountains don’t block the view.

On our evening all-sky chart (above), planets are plotted for each day when the Sun has sunk to 9 degrees below the horizon, at mid-twilight. By then, the two naked-eye planets and eight stars of first magnitude or brighter plotted on the chart are easily visible, except for Pollux and Regulus sinking in the twilight glow. In July, from the Coachella Valley, mid-twilight occurs about 45 minutes after sunset.

Planet positions are represented by a separate dot for each date, with positions for each Monday in July (1, 8, 15, 22, 29), represented by a larger dot and labeled. We find Venus and Regulus in the western sky this month. Rotate the chart until the portion of the horizon circle nearest to the pair is at bottom, and you’ll see the planet and star depicted at the same orientation as they appear in the west to west-northwest sky: Regulus is 25 degrees to the upper left of Venus on July 1, and 12 degrees to the lower right of Venus on July 31.

Another planet is present on July evenings: Saturn, tracking from south to southwest in mid-twilight as July progresses. Notice the first-magnitude star Spica 12 degrees to the west (lower right) of brighter Saturn all month, with the blue-white twinkling star preceding the steady yellowish planet as both objects go westward across the sky.

The brightest star in July’s evening sky is Arcturus, high in south-southwest to west-southwest, above Saturn and Spica, and forming a large triangle with them. When the Big Dipper becomes visible, you can “follow the arc (of the handle) to Arcturus and drive a spike to Spica.”

Next after Arcturus in brilliance is Vega, climbing high in the east-northeast. Compare the contrasting colors of these two stars! To Vega’s lower left is Deneb, and to their lower right is Altair, completing the Summer Triangle. Climbing in the south-southeast to south is reddish Antares, heart of the Scorpion.

Find Regulus, heart of Leo, the Lion, within 5 degrees of Venus during July 18-25. They appear closest on the evenings of July 22 (1.2 degrees apart), and July 23 (1.3 degrees). Sinking lower nightly, Regulus will pass on the far side of the Sun on Aug. 22.

Follow the Moon

During July 10-23, the moon is above the horizon in evening mid-twilight. Follow it nightly as it waxes, or grows, from a thin crescent on July 10, through first quarter (half full) on July 15, to full on July 22. The moon passes, in order, Venus on July 10, Regulus on the 11th, Spica on the 15th, Saturn on the 16th, and Antares on the night of July 18.

I recommend subscribing to the Abrams Planetarium’s Sky Calendar; it illustrates the moon’s changing position against background stars in July, and the changing arrangements of Venus-Regulus at dusk and Mars-Jupiter-Mercury at dawn. For information on subscribing, visit www.pa.msu.edu/abrams/SkyCalendar.

July Moonrise Watch

Full moon at 11:16 a.m. on Monday, July 22, occurs 22 hours after the moon’s third-closest approach of the year, 222,700 miles from Earth.

From the Coachella Valley that evening, the moon rises 17 degrees south of east at 7:48 p.m., about six minutes before sunset. Does the full moon at rising seem unusually large this month? The moon at rising or setting always seems large (the “moon illusion”), even when it is at its most distant from Earth.

For those who enjoy watching or photographing the Moon’s big reddened disk coming up over distant mountains, here are moonrise times for the Coachella Valley for a week, starting at the full moon. Times are when the moon’s disk would just start to appear over an ideal, flat horizon. In practice, our mountainous surroundings may delay risings and hasten settings by several minutes.

Monday, July 22: 7:48 p.m.—17 degrees south of east (full moon)

Tuesday, July 23: 8:32 p.m.—12 degrees south of east (97 percent)

Wednesday, July 24: 9:12 p.m.—6 degrees south of east (92 percent)

Thursday, July 25: 9:50 p.m.—due east (84 percent)

Friday, July 26: 10:25 p.m.—6 degrees north of east (75 percent)

Saturday, July 27: 11:01 p.m.—11 degrees north of east (65 percent)

Sunday, July 28: 11:37 p.m.—15 degrees north of east (54 percent)

Dawn

Our all-sky chart for morning mid-twilight (below) depicts the sky about 45 minutes before sunrise in Southern California. The Summer Triangle of Vega-Deneb-Altair is high in the western sky at dawn, sinking lower as month progresses. During all of July, the Summer Triangle is up all night.

Bright Jupiter emerges by end of first week, low in the east-north east to the lower left of faint (magnitude +1.6) Mars. To their upper left, find bright Capella, the “Mother Goat” star, in the northeast, higher as month progresses. To upper right of Jupiter is reddish Aldebaran, eye of Taurus the Bull, with the compact Pleiades star cluster, or Seven Sisters (not shown), 14 degrees higher. Fomalhaut, mouth of the Southern Fish, drifts from south to south-southwest. By July’s fourth week, Betelgeuse and Rigel, shoulder and foot of Orion, the Hunter, rise from the dawn glow into the eastern sky. (Orion’s belt, a nearly vertical line of three stars midway between them, isn’t plotted.)

Faint reddish Mars and bright yellowish Jupiter appear no more than 5 degrees apart July 11 through Aug. 1, and as close as 0.8 degrees apart on July 22. By July 25, Mercury has emerged as a first-magnitude “star” to their lower left, and brightens to magnitude 0 by month’s end.

The waning crescent moon in the morning sky passes near the Pleiades star cluster on July 4 and 31, near Aldebaran on July 5 and Aug. 1, near Mars and Jupiter on July 6 and Aug. 3-4, and near Mercury on Aug. 5.

Star Parties

The Astronomical Society of the Desert hosts free public sky-watching sessions at Sawmill Trailhead this summer on Saturday evenings, July 6, Aug. 3 and Sept. 7. For more information and directions, visit www.astrorx.org and www.astrorx.org/Sawmill%20Directions.htm.

Robert C. Victor was a staff astronomer at the Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

During evening twilight in June 2013, the brilliant evening “star” Venus gleams very low in the west-northwest, while Mercury lingers nearby during the first three weeks.

Saturn glows yellowish and steadily, well up in the south-southeast to south, contrasting with the twinkling blue-white star Spica just 12 to 13 degrees to Saturn’s west (right).

On our evening all-sky chart, which you can see above, planets are plotted for each day when the sun has sunk to 9 degrees below the horizon, which we call “mid-twilight.” We have chosen that time, because we have found that by then, most planets and stars of first magnitude or brighter are easily visible to the unaided eye. In June, from Palm Springs, it takes 46 or 47 minutes after sunset to reach mid-twilight.

Planet positions are represented by a separate dot for each date, with the positions for each Saturday in June (1, 8, 15, 22, 29) represented by a larger dot and labeled. Using binoculars, folks with unobstructed views may spot Jupiter barely above the horizon on June 1 (look earlier to catch it higher). Rotate the chart until the portion of the horizon nearest to the cluster of planets low in the west-northwest is at the bottom of the circle, and you’ll see the cluster depicted at the same orientation as in the sky: Jupiter 4.5 degrees steeply lower right of bright Venus on June 1, and Mercury nearly as far to Venus’ upper left.

Note that Jupiter drops below the horizon in a couple of days, while Mercury and Venus climb a little higher each evening. Mercury reaches its peak altitude for this apparition around June 8, while Venus slows its climb and begins shifting to the left, or southward. In fact, on June 5, Venus sets the farthest north for this entire evening appearance, then starts a long southward trek until Nov. 6, when Venus will set far to the southwest.

In June, Mercury lingers 5 degrees above Venus for several days around June 6-7, and then starts to move closer to Venus. Pick out the planet dots for June 19; on that date, Mercury and Venus will appear closest, 1.9 degrees apart, with rapidly fading Mercury passing to the south (lower left) of Venus. Mercury dots are shown through June 27, but in practice, we’ll lose sight of it sooner: Mercury fades as it heads down toward the near side of the sun and becomes backlighted. Use binoculars to keep Mercury in view until the last possible date. By the last week in June, Venus will be the only planet remaining of the beautiful compact planet trio we enjoyed in late May.

One other planet resides in our June evening sky: Saturn tracks from south-southeast to south in mid-twilight as June progresses. The reason it drifts that way is that our Earth is moving in orbit around the sun, overtaking the outer planets. Stars on our chart drift westward for the same reason: The revolution of Earth around the sun. Notice the blue-white first-magnitude star Spica 12 to 13 degrees to the west (right) of Saturn and preceding it as both objects go westward across the sky. The stars’ daily positions aren’t plotted as individual dots, but are simply represented by tracks as the stars go west (counter-clockwise around the North Star) in the course of the month, or during a single night.

The brightest star in June’s evening sky is Arcturus, high above Saturn and Spica, and forming a large triangle with them. When the Big Dipper becomes visible, you can “follow the arc (of the handle) to Arcturus and drive a spike to Spica.”

Next after Arcturus in brilliance is Vega, climbing in the northeast. Compare the colors of these two stars! To Vega’s lower left is Deneb, and ascending into view later in the evening or later in the month is Altair, completing the “Summer Triangle.” Climbing in the southeast is reddish Antares, heart of the Scorpion.

In the west to northwest in early June is a curved arch of four stars topped by Pollux (and Castor, not shown, because at magnitude 1.6, it’s just a little fainter than the magnitude 1.5 brightness limit of our chart). These two stars make up the heads of Gemini, the Twins. To the Twins’ lower left is Procyon, the Little Dog Star, and in the northwest, anchoring the northern end of the arch, is Capella, the Mother Goat Star, ranking next after Vega in brightness.

Ranking last in brightness of the 16 stars of first magnitude or brighter visible in the course of a year from Southern California is 1.4-magnitude Regulus, heart of Leo, the Lion. Watch Regulus descend the western sky during June and July, before it passes on the far side of the Sun around August 23.

Follow the Moon

During June 10-23, the moon is above the horizon in evening mid-twilight. Follow it nightly as it waxes, or grows, from a thin crescent on June 10, through first guarter (half full) on June 16, to full on the night of June 22-23. The moon passes, in order, Venus and Mercury on June 10, the Twins on June 11, Regulus on June 13 and 14, Spica and Saturn during June 17-19, and Antares on June 21.

(The Abrams Planetarium monthly Sky Calendar illustrates such gatherings of moon, planets, and stars. To view a sample issue, visit www.pa.msu.edu/abrams/SkyCalendar.)

Full moon at 4:32 a.m. PDT on Sunday, June 23, nearly coincides with the moon’s closest approach of the year, 221,824 miles from Earth.

From the Coachella Valley on Saturday, June 22, the moon rises in the east-southeast at 7:22 p.m. PDT, about 38 minutes before sunset. On Sunday morning, June 23, the moon sets in the west-southwest at 5:55 a.m., 19 minutes after sunrise (after the moon has been up all night). And on that Sunday evening, the moon rises in the east-southeast at 8:21 p.m., some 21 minutes after sunset.

Does the full moon at rising or setting seem unusually large this month? Note that the moon at rising or setting always seems large (the “moon illusion”), even when it is at its most distant from Earth.

For those who enjoy watching or photographing the Moon’s big reddened disk coming up over distant mountains, here are moonrise times for the Coachella Valley for a few evenings after full. Times are when the foon’s disk would just start to appear over an ideal, flat horizon. In practice, our mountainous surroundings may delay risings and hasten settings by several minutes.

Monday, June 24: 9:13 p.m.

Tuesday, June 25: 9:59 p.m.

Wednesday, June 26: 10:40 p.m.

Thursday, June 27: 11:17 p.m.

Friday, June 28: 11:52 p.m.

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

On six evenings—from Friday, May 24, through Wednesday, May 29, including all of the Memorial Day weekend—three bright planets will form a “trio,” fitting into a 5-degree field of view, low in the west-northwest sky at dusk.

Ordinary binoculars, with magnifications of 7- to 10-power, will take in all three planets—Venus, Mercury and Jupiter—simultaneously. Due to the differences in the speeds of the planets in their orbits around the sun, the arrangement of the planets will change from one night to the next.

Illustrations of the nightly arrangements of the planets appear on the Abrams Planetarium Sky Calendar, available online at www.pa.msu.edu/abrams/SkyCalendar.

Saturn will also be visible, well up in the southeastern sky on the dates of the trio, May 24-29. A telescope will easily show Saturn’s rings.

On Friday, May 24, the first evening of the trio, Venus is within 4 degrees (to the lower right) of Jupiter, while Mercury passes within 1.4 degrees to Venus’ upper right. (As a side note: The full moon tonight will be the brightest of the year.)

For the next several evenings, while the planets are in their tightest gatherings, it will be easy to notice changes in their arrangement. If you observe at the same stage of twilight each evening—for example, 30 minutes after sunset, or 45 minutes after sunset—you’ll notice the distant, slow-moving outer planet Jupiter dropping about 0.7 degrees lower each night, while the brighter inner planet Venus—on the far side of its orbit and gaining on Earth—climbs about 0.2 degree higher each night. Speedy Mercury, during the six evenings of the trio, climbs 0.6 to 0.8 degrees higher each night.

On Sunday, May 26, the evening of the most compact gathering, two planets appear within 2 degrees of Venus (the brightest planet): Jupiter to Venus’ upper left, and Mercury to Venus’ upper right. On the same evening, Mercury passes 2.4 degrees to Jupiter’s upper right.

On Monday, May 27, the compact gathering is still striking as brilliant Venus moves 1.2 degrees to the right of Jupiter, while Mercury stands 2.4 degrees above Venus, and 2.7 degrees to the upper right of Jupiter.

On Tuesday evening, May 28, the two brightest planets appear closest to each other, as Venus passes just more than 1 degree to the upper right of Jupiter. Find Mercury 2.8 degrees above Venus.

By Wednesday, May 29, the planets will have reversed their order of a week earlier. Now Mercury is the highest (within 3.3 degrees above Venus), and Jupiter is the lowest (1.7 degrees below Venus). This is the last evening all three planets fit within a 5-degree field. However, the three planets will remain in a nearly straight line for several more days as they spread farther apart.

Within the first few days of June, Jupiter will be gone, as it sets ever earlier in bright twilight before its conjunction on the far side of the sun on June 19.

Mercury will linger about 5 degrees to the upper left of Venus from June 3-10, before heading down to pass within 2 degrees lower left of Venus on June 19. Mercury will fade from view within a few days later, as it heads between the Earth and sun and becomes more backlit.

Venus will keep us company at dusk until early January 2014. In November and December 2013, Venus will attain its highest position in the evening sky this time around, with its greatest brilliancy, and will display its visually most-interesting crescent phases.

Saturn remains in the evening sky, passing through the south at dusk in June, and sinking into the west-southwest twilight glow in October. Before then, Venus will pass 3.5 degrees to the lower left of the ringed planet on Sept. 17 and 18.

Observing the trio from the Coachella Valley

Any place with a good view of sunset is fine for viewing the planet-gathering on the evenings of May 24-29. Among the best places in the Coachella Valley are those with a view of Banning Pass toward the west-northwest.

Start looking for the planets early, low in the west-northwest, where twilight is brightest, within 30 minutes after sunset. By then, brilliant Venus will be visible, closely accompanied by Jupiter. Continue until at least 45 minutes after sunset. As the sky darkens, Mercury will also be seen. Sunset in the western Coachella Valley occurs at 7:47 p.m. on May 24, and at 7:50 p.m. on May 29.

An astronomer will be on hand to assist folks in viewing the compact gathering of planets from 8:15 to 8:40 p.m. on the following evenings. Bring binoculars for the best views. After following the trio of Venus, Jupiter, and Mercury, we’ll use a telescope to view Saturn’s rings:

Saturday, May 25: In the northern part of Palm Springs, meet in Victoria Park on Via Miraleste just south of Vista Del Monte Elementary School at 8:15 p.m.

Sunday, May 26: In Idyllwild, location to be announced.

Monday, May 27: In the northern part of Cathedral City, meet on the west side of San Eljay Avenue just north of 30th Avenue at 8:15 p.m. That’s across San Eljay from the southwest entrance of James Workman Middle School. The location has a fine view toward Banning Pass.

How unusual is this gathering of planets?

The compact gathering of Venus-Jupiter-Mercury low in the west-northwest at dusk is a rare event especially worthy of observation. There will be only 14 other trios of planets (when all fit within a 5-degree field) before 2050. Of these, the next one, of Venus-Mars-Jupiter in the morning sky in October 2015, will be the most impressive, more 30 degrees up in dawn mid-twilight. With daylight saving time in effect in October, planet-gazers won’t have to get up very early to see that wonderful gathering in autumn of 2015.

For the next evening trio as good as this month’s gathering, with the planets clustering more than 4 degrees up in the middle of twilight, we’ll have to wait until September 2040.

So take advantage of this weekend’s opportunity to see three planets gather. Many years will pass before planet-watchers can enjoy as favorable a view of a similar event in the evening sky.

Robert Victor is the former as staff astronomer at Abrams Planetarium at Michigan State University.

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