California Skies for December 2021 - January 2022
By Robert C. Victor. Twilight charts provided by Robert D. Miller
December highlights: Venus bright enough for daytime naked-eye, of peak interest for optically aided viewing, and a spectacular pairing with a crescent Moon. An eye-catching lineup of three evening planets all month, with a fourth joining the party before Venus checks out in early January. A few hours of dark moonless skies coinciding with the year’s best meteor shower. An extra-bright Moon, a northernmost Moon, and a southernmost Sun, all in a 3-day span. And two celestial gifts on the last day of 2021: A compact dawn gathering of an old crescent Moon with a planet and its namesake star; and the Dog Star reaching its high perch in time to howl at midnight.
Our evening twilight sky map shows the positions of the naked-eye planets and the brightest stars at mid-twilight, when the Sun is 9° below the WSW horizon. [See monthly links under The Sky at Dusk, below.] In December, this occurs nearly 45 minutes after sunset. Throughout the month, a lineup of three planets dominates the southwest quadrant of the sky. Brilliant Venus, in SW to WSW, anchors the lower right end of the lineup. In the first two weeks, Venus gleams at mag. –4.9, as bright as it gets, and fades to mag. –4.3 at month’s end. Jupiter, next in brightness at mag. –2.3 to –2.1, marks the upper left end of the lineup. Jupiter’s distance from Venus is 34.5° on December 1, shrinking to 31.4° on December 14, and expanding to 37.5° on December 31. Saturn, at mag. +0.7, lies between the two brighter planets.
Moon passages (evenings): Follow the Moon at dusk December 5-18. [See link to December Sky Calendar, below.] The arrangement of Moon and three bright planets is especially attractive as Moon grows from a thin young crescent 15° lower right of Venus on December 5, through First Quarter phase, when the Moon is half full, 90° from Sun, and 23° east of Jupiter, on December 10. The very best evening is Monday, December 6, when the 11-percent Moon appears 2.6° lower left of Venus at dusk. Don’t miss that! For several hours that day, we are presented with an easy opportunity to spot Venus in the daytime. Try looking when the 10-percent crescent Moon passes due south, 30° up on December 6, at 2:19 p.m. PST in Palm Springs, for example. Venus then appears 3.2° to the Moon’s upper left. A telescope magnifying only 45-power would make the 24-percent crescent Venus appear the same apparent size as the Moon with an unaided eye. And with Venus at its brightest, a Moon-Venus pairing seldom gets better than this! The Moon will close in on Venus until they set, more than 2½ hours after sunset, when they’re 2.4° apart.
On the next evening, Tuesday, December 7, Saturn will appear 5° upper right of the 19% crescent Moon. On Wednesday, December 8, find Jupiter within 7° to the 29% crescent Moon’s upper left at dusk. Four hours later, when they’re about to set, they’ll be just over 5° apart. On Thursday December 9, the 40% fat crescent Moon is 10° east of Jupiter.
One week later, on December 16, the 96% Moon is 5° from the Pleiades and within 9° of Aldebaran. On the next evening, find Aldebaran within 8° lower left of the 99% Moon.
Through the telescope: Venus appears larger than Jupiter in all of December, because it’s unusually close to Earth. Inferior conjunction, Venus nearly between Earth and Sun, will occur on January 8. Venus grows more than 50 percent in apparent size this month, ending up more than one arcminute (1/60 degree) across. At that size, a magnification of 30-power would make Venus appear about as large as the Moon with an unaided eye! Venus is bright enough to be spotted in daylight. In December 2021, find Venus to upper left of setting Sun, by 41° on December 1; by 36° on December 10; by 32° on December 16; by 26° on December 21; by 17° on December 28; and by 13° on December 31. If using optical aid such as a telescope or binoculars, be sure to block the Sun from view or wait until it sets in late December or early January, when Venus appears close to the Sun. Even binoculars easily resolve Venus’ crescent phases: 28 percent illuminated on December 1; 20% on December 10; 15% on December 16; 10% on December 21; 5% on December 27; 3% on December 30; and 2% on January 1.
Saturn with its ring system (still 18° from edgewise) and Jupiter with its dark cloud belts and four large satellites discovered by Galileo in 1610 are always impressive for telescopic viewing.
On December 1 at dusk, look for the Summer Triangle of Vega, Altair, and Deneb, in order of brightness, well up in the western sky. On that date, a line from Vega to Altair, 34° long, extended 31° to the south ends at Saturn, which is then 18.1° upper left of Venus and 16.5° lower right of Jupiter.
Other bright stars: Look in S to SSW at dusk for Fomalhaut, mouth of the Southern Fish, 22° to 20° lower left of Jupiter. Watch for yellowish Capella, the Mother Goat star, ascending in NE, and red-orange Aldebaran, ascending in ENE to E, 31° lower right of Capella. On December 1, Aldebaran is at opposition as Earth passes between that star and the Sun. Look for Aldebaran low in ENE at dusk and low in WNW at dawn, as shown on the evening and morning twilight maps. Although Aldebaran marks the eye of Taurus the Bull, its name translated from Arabic means “the Follower”, of the beautiful Pleiades or Seven Sisters star cluster, not plotted on the maps. Aim your binoculars 14° above Aldebaran as darkness falls, and enjoy!
As December progresses (or later in the evening), watch 21° below and 26° lower right of Aldebaran for Orion’s two brightest stars, 19° apart: Reddish Betelgeuse rising north of east, and blue-white Rigel rising south of east. Within 45 minutes after you first spot them, look for the “Twin” stars of Gemini, Castor and Pollux, 4.5° apart, rising farther north, 30°-34° below Capella.
The Geminid meteor shower reaches its peak in the predawn hours of Tuesday, December 14. The bright waxing gibbous Moon sets four hours before sunrise, leaving 2½ hours of dark skies for excellent viewing of “shooting stars” until dawn brightens. Meteors can light up anywhere in the sky, but the tracks of Geminids, extended backward, will all radiate from a common point, not far from the star Castor in the constellation Gemini. Morning twilight gets underway about 1½ hours before sunrise, as the Pointer Stars of the Big Dipper stand directly above the North Star.
Later that same Tuesday, in the evening, we witness the least span of the three bright planets, Venus-Saturn-Jupiter, 31.4°. Two days later, on Thurs. December 16, Venus approaches to within 14° west of Saturn, but no closer! Venus commences retrograde, or westward motion against the stars, on night of December 18-19.
Opposition surge: The Full Moon on Saturday evening, December 18 will shine with extra brilliance, because it will lie just outside the Earth’s shadow and reflect much of its light back toward Earth. On the next evening, Sunday December 19, witness this month’s northernmost moonrise, 32° north of east, about half an hour after sunset for southern California. Northernmost moonset will take place the next morning, 32° north of west, about 1.4 hours after sunrise from SoCal. (Note: If you have surrounding mountains, that would delay moonrise and hasten moonset.) Midway in time between Sunday evening’s moonrise and Monday morning’s moonset, soon after midnight very early on Monday morning, the Moon passes just south of overhead. High Moon!
Winter begins on Tuesday, December 21 at 7:59 a.m. PST, when the Sun stands directly over the Tropic of Capricorn, lat. 23.4° south. Californians have their lowest midday Sun of the year that day, when the Sun passes directly south. For Palm Springs, this occurs 33° above the horizon, at 11:44 a.m.
In the evening sky in late December 2021, Venus descends into the twilight glow, and displays a large, ever thinner crescent until its departure in early January. Even ordinary binoculars will resolve the crescent. Look very soon after sunset, to mute the contrast of brilliant Venus against the darkening sky.
A fourth planet, Mercury, adds its bright presence (mag. –0.7) in the last ten days of the month. On December 22, find it 12° lower right of Venus. On December 25 Mercury is 7° below Venus. On December 28, Mercury passes 4.2° south (lower left) of Venus. The planets are moving in opposite directions, as Mercury is emerging from the far side of the Sun, and Venus is on the near side, plunging toward its inferior conjunction of January 8. On December 30, Mercury appears 5.5° to the left of sinking Venus, and on December 31, 7° to Venus’ upper left. (Mercury remains in view until mid-January, but fades to mag. 0 by January 12, and to mag. +1 by January 15.)
New Year’s Eve: On December 31, Venus sets in WSW 65 minutes after sunset. Getting noticeably lower with each passing day, Venus now sets 7 minutes closer to the time of sunset daily. Jupiter is in SW at dusk, 37.5° upper left of Venus. Saturn is 19° upper left of Venus and nearly 19° lower right of Jupiter. Mercury is within 7° upper left of Venus and 14° lower right of Saturn.
On the last day of the year, the Sun reaches its highest point in the south at midday, which occurs at 12:03 p.m. PST as seen from longitude 120° west, and about four minutes earlier per degree of longitude you are east of that longitude, or later if you’re west of it. Almost exactly 12 hours later, and therefore in the middle of the night, Sirius, the Dog Star, reaches its high point on New Year’s morning, at 12:02 a.m. PST as seen from longitude 120° west.
So, in the waning minutes of 2021, step outside and look toward the south. Since the Moon and naked-eye planets will all then be below the horizon, Sirius will stand out as the brightest object in the sky, a fitting occasion to close the year by reading Robert Frost’s poem, Canis Major. [See links, below.] Notice that the 3-star belt of Orion, if extended, points directly to Sirius.
Earlier that evening, in bright twilight just after sunset, binoculars show Venus as a thin crescent 2.4 percent illuminated, and just more than one arcminute across, and 13° upper left of the setting Sun. On the next evening, January 1, the Venus crescent is 2 percent lit and 11.6° upper left of setting Sun. (Important: For eye safety, when Venus draws within several degrees of the Sun, look just after sunset, or just after the Sun’s disk has disappeared behind your local horizon landscape features.) On January 4, Venus will appear within 8° above the setting Sun. On January 7 and 8, an extremely thin crescent Venus will pass within 5° upper right of the setting Sun. On what evening in early January will you last spot Venus?
The four brightest stars in morning twilight in December, in order of brightness, are Sirius, visible early in the month, until it sinks below horizon in WSW; Arcturus, very high in E to ESE; Vega, climbing in NE; and Capella, dropping lower in NW. [See link to The Sky at Dawn, December 2021, below.] The only morning planet is Mars, which is faint, mag. +1.6 to +1.5, low in ESE to SE. On December 18, Mars passes 1.0° S of 2.6-mag. Beta Scorpii, northernmost of three bright stars in the head of the Scorpion. Watch for the emergence of brighter, 1.1-mag. Antares, heart of the Scorpion, within 8° below Mars that morning. By December 24, Antares is 5° to the lower right of Mars. On December 27 and 28, Mars passes 4.5° N (upper left) of the star. Note their similar reddish colors, which influenced the naming of the star Antares. In a beautiful compact gathering on the morning of December 31, Mars and Antares are 5.2° apart, with a 7-percent waning crescent Moon between and slightly above them, slightly more than 3° from each. Best time to look might be one hour before sunrise. Look about 9°-11° above the southeastern horizon. Binoculars recommended.
Follow the Moon in the morning sky December 18-January 1. On December 20, the 98% Moon is 10°-11° below Pollux and Castor. On December 21, the 95% Moon is 3.5° from Pollux and 8° from Castor. On December 24 the 75% Moon is 5° from Regulus. On December 28, the 34% crescent Moon is 5° from Spica. On December 31, the 7% crescent forms a striking gathering with Antares and Mars, as described above. On January 1, binoculars are recommended to catch the last old Moon, a 2% crescent, 12° lower left of Mars.
Illustrations of many of these events appear on the Abrams Planetarium monthly Sky Calendar. [Follow links to current issues below.] To subscribe for $12 per year or to view another sample, visit www.abramsplanetarium.org/skycalendar/
Mentions of star patterns in literature
Locksley Hall, by Alfred, Lord Tennyson:
These lines from Tennyson’s Locksley Hall describe the stars of Orion descending the western sky, perhaps during morning twilight on a date in November, or sometime in darkness hours on a night from December through March, or during evening twilight on a date in April:
“Many a night from yonder ivied casement, ere I went to rest,
Did I look on great Orion sloping slowly to the West.”
The next lines in the same poem describe the Pleiades as they ascend the eastern sky at dusk on an evening in November or early December:
“Many a night I saw the Pleiads, rising thro' the mellow shade,
Glitter like a swarm of fire-flies tangled in a silver braid.”
The poem, Canis Major, by Robert Frost, describes Sirius and the constellation of the Big Dog prancing across the southern sky:
Another Frost poem, The Star-splitter, opens with a description of the rising of Orion over the eastern horizon, a striking sight that can be witnessed at dawn in late July, and two hours earlier each month, until dusk in late December. The map, November Evening Skies (link below), depicts Orion just rising in the east during early evening hours, half an hour earlier each week, in November and December:
“You know Orion always comes up sideways.
Throwing a leg up over our fence of mountains,
And rising on his hands, he looks in on me…”
The complete poem tells an amusing story of a farmer who devised a scheme to purchase a telescope so he could split stars. Enjoy!
Here are monthly evening and morning mid-twilight sky maps through January 2022. Use them to follow seasonal changes in positions of bright stars, and wanderings of the planets.
THE SKY AT DUSK THE SKY AT DAWN
Here are Sky Calendars and detailed evening sky maps for December 2021 and January 2022. The evening sky map for November, depicting Orion just rising, can still be used through the end of December, early in the evening.
SKY CALENDAR EVENING SKIES
January 2022 begins with Orion rising sideways at dusk and an exodus of naked-eye planets from the early evening sky, from four down to only one, Jupiter. The morning sky begins with one planet, faint Mars, and adds brilliant Venus in the second week. (Mercury begins a detectable morning presence a day or two into February.) New Moons on Jan. 2 and 31 make the Moon’s cycle of phases neatly fit within the calendar month. All Moon-planet pairs this month, indeed until mid-May, involve a lunar crescent. With slight optical aid, Venus itself shows an impressive crescent!
January evening sky [see map S202201P.pdf]: The year 2022 opens with a fine display of four bright planets spanning an arc of 38° in the southwest sky at dusk. On January 1, starting with the lowest and progressing to upper left, they are brilliant Venus, Mercury, Saturn, and Jupiter. But choose a spot with unobstructed views toward the west-southwest horizon, especially to catch the two planets interior to Earth’s orbit, because both, very low at dusk, will pass inferior conjunction, nearly between Earth and Sun, Venus doing so on Jan. 8, and Mercury on Jan. 23.
Even if buildings or a mountain blocks your view, you can still spot Venus, because it’s brighter than mag. –4, and easy to find in the daytime, using just a pair of binoculars. Protect your eyes! Be sure the Sun is hidden before you search for Venus. On Jan. 1, when Venus sets within an hour after the Sun, try for it in late afternoon or at sunset, within 12° upper left of the Sun. Venus is now unusually close to Earth and backlighted by the Sun, and shows a crescent shape easily resolved in binoculars. On Jan. 3, the crescent is only 1 percent illuminated and appears just more than 1 arcminute across. With each passing day, Venus appears closer to the Sun, sets earlier, and displays an even thinner crescent. On Jan. 4, Venus is within 8° directly above the late afternoon Sun and sets 38 minutes after it. If the sky is very clear on Jan. 8, by using binoculars or a telescope, you can try for the planet’s hyper-thin crescent within 5° upper right of the known location of the Sun. Just be sure that the Sun is hidden from view when searching so near to it in the sky.
Mercury begins the year at mag. –0.7, quite bright, and fades only slightly to mag. –0.5 as it reaches its highest position 5° lower right of Saturn on Jan. 8. Four days later, on Jan. 12, Mercury at mag. 0.0 approaches within 3.4° lower right of fainter Saturn at mag. +0.7. The event is called a quasi-conjunction, because Mercury approaches Saturn but won’t pass it until after retrograding and returning to finally overtake it, in the morning sky in early March.
Mercury fades to mag. +1.0 by Jan. 15, and very quickly in following days, so it disappears in the bright evening twilight before reaching the horizon. Saturn holds steady in brightness, but drops lower on its way to solar conjunction on Feb. 4. Before then, Saturn sets in mid-twilight on Jan. 24. Then Jupiter becomes the only naked-eye evening planet, until it, too, disappears, in the third week of February. Uranus and Neptune can be picked up with binoculars, with the aid of good finder charts. Visit www.abramsplanetarium.org/msta/.
The eastern evening sky is filling with winter’s bright stars. In early January you can still catch Orion low, as described in the opening lines of Robert Frost’s amusing poem, The Star Splitter:
"You know Orion always comes up sideways.
Throwing a leg up over our fence of mountains,
And rising on his hands, he looks in on me…”
Low in the eastern sky, 19° apart, are Orion’s brightest stars, blue-white Rigel, his foot, and reddish Betelgeuse, his shoulder. Midway between them, look for three stars in a nearly vertical line (not shown on our chart), marking the Hunter’s belt. As the evening progresses, or as days pass, if you observe at the same stage of twilight each evening, Orion rises higher, making room below for his “Dog Stars” to appear: Procyon, the “before the Dog” star, rising a few degrees north of east, and Sirius, the “Dog Star” itself, rising in ESE. Note the line of belt stars, extended downward, locates Sirius, the brightest star in the night sky.
Sirius, Procyon, and Betelgeuse form the nearly equilateral Winter Triangle. If you look while Sirius is still very low, you can still see the entire Summer Triangle in NW to west. In order of brightness, its stars are Vega, Altair, and Deneb.
In early January, Sirius rises in a dark sky. It will then flash vigorously, in many colors. From southern California, catch Sirius and Altair at equal altitudes, a bit more than 4° above opposite horizons. This occurs two hours after sunset on Jan. 2, at end of twilight on Jan. 9, and about one hour after sunset on Jan. 14 and 15. If mountains or buildings don’t block your view, you can see the Summer and Winter Triangles simultaneously.
January morning sky [see map S202201A.pdf]: In early January, before Venus emerges, the brightest points of light are golden orange Arcturus high in SE to S, blue-white Vega climbing in ENE, and yellow Capella low in NW. Capella, Castor, Pollux, and Procyon form an arch sinking in NW to W. Spica is in S to SW, 33° from Arcturus. Regulus is in western sky, 37° upper left of Pollux.
Altair rises just north of east before mid-month and competes the Summer Triangle with Vega and Deneb. Around Jan. 15 each year the figure is equally visible at dawn and at dusk.
Antares is low in SE at dawn at the start of January each year. On Jan. 1, 2022, Mars is 5.6° left of Antares. About 40 minutes before sunrise, look for the old crescent Moon, 2 percent full, 12° lower left of Mars and 15° lower left of Antares. From southern California, the Moon is about 28 hours before New.
Imagine a competition between two red objects, Mars and Antares, to determine which is brighter. At the start of 2022, first-magnitude Antares beats Mars (mag. +1.5) by about half a magnitude, but in December 2022, Mars, at opposition and making a close approach to Earth, will reach mag. –1.8, outshining Sirius, the brightest star.
Mars in Jan. 2022 moves eastward against the background of zodiacal stars by 0.7° per day. By Jan. 9, Mars will be 10° lower left of Antares; on Jan. 16, 15°; and on Jan. 30 and 31, 25°.
During the second week of Jan. 2022, Venus starts to be visible in the morning. On Jan. 8 and the days immediately following, use binoculars or a telescope to observe the emerging thin crescent Venus, again taking care to look only when the Sun is completely hidden. On Jan. 8 Venus rises only 13 minutes before sunup, and the extremely thin crescent is within 5° upper left of the hidden Sun’s position. On Jan. 12, Venus rises 40 minutes before sunup and the easier one-percent crescent is 8° directly above the rising Sun. By Jan. 20, Venus rises nearly 1.5 hours before sunup, and the 5-percent crescent is 19° upper right of the rising Sun. On Jan. 26, Venus rises 1.9 hours before the Sun, and displays a 10-percent crescent 26° upper right of the Sun. On Jan. 31, from southern California, Venus rises 2.2 hours before sunup, and displays a 15-percent crescent 31° upper right of the Sun. In February, about five weeks after its January 8 inferior conjunction, Venus reaches its greatest brilliancy.
On such occasions, it’s easy to spot Venus in the daytime. Just find Venus before sunrise, and keep track of it. A small telescope, or even binoculars, will reveal the crescent!
Chances to observe Venus in its impressive crescent phases come only during the interval lasting for several weeks before and after an inferior conjunction of Venus, which occurs at intervals of 19.2 months. So take advantage of the current window of opportunity centered on January 8. The next time Venus displays a crescent will be during the weeks leading up to and following the inferior conjunction of August 13, 2023.
As Venus transitions from evening sky into morning sky, it is retrograding, or going west against the background stars of the zodiac constellations. Venus ends retrograde on Jan. 29. Venus pauses 10° east of 3rd-mag. Lambda Sagittarii, top star of the Teapot asterism. Mars, moving eastward, passes 1.6° above that star on Feb. 2. Even after Venus resumes eastward motion, it moves slowly at first, so Mars will continue to close in on Venus. Venus-Mars are 20° apart on Jan. 17; then 15° apart on Jan. 22; and 10° apart on Jan. 30. The gap will slowly close, to 5° on March 1, and to just less than 4° in mid-March.
Mercury will brighten to mag. +1.0 by Feb. 1, some 14° lower left of Venus. Saturn will bring the morning planet total to four in last week of February, before Mercury overtakes it on March 2. Mercury sinks back into bright twilight, dropping the number of planets to three, before Jupiter emerges in late March to bring the morning planet total back up to four.
Moon in January 2022. We’re in the midst of a period, lasting from mid-November 2021 through mid-May 2022, when all of the five bright planets appear within 90 degrees of the Sun. Accordingly, all Moon-bright planet conjunctions during those six months involve a crescent Moon, which I think are visually the most appealing.
We’ve already described the old Moon to lower left of Mars on morning of Jan. 1. Astronomical New Moon, invisible, occurs on Jan. 2 at 10:33 a.m. PST. Just 31 hours later, at dusk on Jan. 3, the young, 3-percent crescent Moon will be 4° up in SW to WSW. Venus will then be setting 12° farther to the right (look earlier to catch it). Mercury will be within 4° to upper right of the lunar crescent. Saturn will be 10° upper left of Mercury, and finally, bright Jupiter will be 19° upper left of Saturn.
For the next three evenings, Jan. 4-6, watch the waxing crescent Moon ascend past the planets. On Jan. 4, Saturn is within 6° to right of the 8-percent Moon and slightly lower. Mercury is within 13° lower right of the Moon. Jupiter is 16° to Moon’s upper left.
On Jan. 5, Jupiter is within 5° to Moon’s upper right. Moon is 15 percent full. Saturn and Mercury are respectively 18° and 25° to Moon’s lower right. Venus now sets only half an hour after sunset.
On Jan. 6, the Moon is at 24 percent. Jupiter is 13° to its lower right.
Moon spends three nights in Taurus: On Jan. 12, the Moon is 4° S of the Pleiades star cluster, while Mercury pauses 3.4 ° lower right of Saturn in a quasi-conjunction. On Jan. 13, the Moon passes 6° N of Aldebaran, eye of the Bull. On Jan. 14, the Moon passes within 4° S of Beta Tauri (Elnath, tip of the Bull’s northern horn).
On the evening of Jan. 16, the Moon is 7° from Pollux and Castor, the bright “Twin” stars of Gemini, and appears only 3°-4° south of Pollux the next morning. On Jan. 17, the Full Moon rises a few minutes before sunset and appears 7° below Pollux as the sky darkens. On Jan. 18, the Moon rises in twilight, only about 45 minutes after sunset.
After the Full Moon of Jan. 17, follow the waning Moon each morning through Jan. 30. On Jan. 20, the gibbous Moon (93%) is 4° N of Regulus, heart of Leo, the Lion.
On Jan. 24, the 61-percent Moon, one day before Last Quarter phase, is 5° N of Spica, spike of grain in the hand of Virgo.
On Jan. 27, the 28-percent crescent Moon is within 7° upper right of Antares, heart of the Scorpion.
On Jan. 28, the 18-percent crescent Moon is 9° lower left of Antares. Find dim Mars 14° to Moon’s lower left, and brilliant Venus 11° left of Mars.
On Jan. 29, the Moon is 10 percent illuminated and 3° lower right of Mars. Venus is 10.4° left of Mars.
On Jan. 30, the 4-percent crescent Moon is 13.5° below and slightly right of Venus. Mars is 10° right of Venus and slightly lower.
On Jan. 31, there is no Moon to be seen. (New Moon occurs at 9:46 p.m. PST.) Mars is 9.4° left of Venus and 2.2° above 3rd-mag. Lambda Sagittarii, top star of the Teapot. Mars will pass 1.6° N of this star on Feb. 2. Using binoculars, can you spot Mercury, of mag. +1.3, and 14.4° lower left of Venus? Mercury brightens in coming days and lingers 13° lower left of Venus Feb. 3-9.
Illustrations of many of the events described above appear on the Abrams Planetarium monthly Sky Calendar. To subscribe for $12 per year or to view a sample copy, visit www.abramsplanetarium.org/skycalendar/.