Extra Content
Sometimes on the Sky Calendar, additional additional files, extended notes, and other activities are mentioned. They can be found here and are provided by Robert C. Victor, Robert D. Miller, and Jeff Hunt for those who find them useful.
Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs.
Robert D. Miller, who provided the twilight charts and the planet orbit charts, 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.
This expanded version of the left margin notes of the Abrams Planetarium Sky Calendar for May 2026 contains details about the unusually bright, sudden emergence of Mercury into the evening sky in late May, and the Blue Moon of May 31. Also provided is a link to a sky-watching activity following bright stars in the western sky until their annual disappearance, and a set of monthly charts depicting the sky at morning and evening mid-twilight for the rest of this year.
May’s evening twilight scene is dominated by two brilliant planets, Venus of mag. –4 low in west-northwest, and Jupiter of mag. –2 in west, to Venus’ upper left. At dusk mid-twilight on May 1, Jupiter is halfway from horizon to overhead and nearly 40° from Venus. The gap between them closes to 30° on May 10; to 20° on May 20; and to within 9° on May 31, all building up to their spectacular conjunction on June 9. Both planets are moving east against the starry background, while the zodiacal backdrop itself is sinking lower in the west as weeks pass, a consequence of Earth’s revolution around the Sun. Jupiter this month shifts daily by 0.14° to 0.19°, while fast-moving Venus goes 1.2° daily, bringing it closer to Jupiter.
Many of the sky events described below are illustrated on the Abrams Planetarium Sky Calendar. For $12 per year, subscribers receive quarterly mailings, each containing three months of calendars and evening star maps. Subscription info and a free printable sample of the May 2026 calendar and sky map are available at
https://abramsplanetarium.natsci.msu.edu/sky-calendar/index.aspx
Watch the changing configurations of Venus and Jupiter with stars of Taurus and Gemini. Plenty of photo-ops! On May 1, watch Venus pass just more than 6° north (upper right) of Aldebaran, eye of Taurus. Farther left, in the west-southwest, look for Orion, with his 3-star belt pointing left to Sirius, the brightest star, twinkling in southwest. Follow these stars and others until their annual exits from the western sky. Record your observations on the Daily Skywatch Log, posted with info on other sky events, on the Sky Calendar Extra Content Page, at https://abramsplanetarium.natsci.msu.edu/sky-calendar/extra-content.aspx
Watch these evening events: May 12, Venus 4.0° S of Beta Tauri, tip of the Bull’s N horn, and between the horns the next evening; May 17, Young crescent Moon, 3% full with earthshine, low in WNW at dusk, 14° lower right of Venus. Look nightly for rest of May and watch Moon pass two brilliant planets and four first-mag. zodiacal stars; May 18, spot Venus in the daytime! Look near the 8% crescent Moon in west shortly before sunset, with Venus 2°-3° to its lower left, impressive for unaided eye and binoculars. As the sky darkens after sunset, a spectacular conjunction awaits!
On the next evening, May 19, the 16% crescent Moon climbs to 14° upper left of Venus and 7° lower right of Jupiter. Note the “Twin” stars Pollux and Castor, 4.5° apart, within 9° above the Moon, and 6°-10° upper right of Jupiter.
May 20, Mercury at mag. –1.6 sets 40 min after sunset, so look for it earlier, with optical aid, within 25° lower right of Venus. For details on this very favorable apparition of Mercury, see Extra Content Page. By an hour after sunset on May 20, Mercury has set, but the 25% Moon appears 8° upper left of Jupiter and left of the Twins.
On May 20 and 21, Venus sets farthest north along the horizon, farther north than even the setting Sun on the first day of summer, June 21. For the rest of Venus’ evening apparition ending in early October, watch Venus’ setting point shift progressively farther south along the western horizon.
May 25, Venus forms an isosceles triangle with Jupiter and Castor, nearly 15° from each; Mercury at mag. –1.1 is now easy for unaided eye, 20° lower right of Venus; May 26-31, Jupiter within 6.3° S of Pollux; May 30, Jupiter forms isosceles triangle with Pollux and Castor, 10.3° from each.
Special event, night of May 30-31: There are two Full Moons this month, one on May 1 at 10:23 a.m. PDT, and the second one on May 31 at 1:45 a.m. PDT. Since the red supergiant star Antares, heart of Scorpius, is at opposition to the Sun on the night of May 30-31, the Full Moon overnight will appear close to that star all night. Closest approach, with Antares within 1.0° above Moon’s northern edge, occurs on the morning of May 31, shortly after 3:00 a.m. in the Coachella Valley. Since this is the most distant Full Moon of the year, and it is a “Blue Moon”, then we have a Blue Micromoon in conjunction with a red supergiant star! After the “Blue Moon” overnight on May 30-31 (links to definitions, see below), the next one, if defined as the second Full Moon in a calendar month, as in today’s example, will take place on December 31, 2028. But if a Blue Moon is defined as the third Full Moon of a season with four, then tonight’s was not a Blue Moon, and the next will occur on May 20, 2027.
In morning twilight: Use binoculars to spot 0.9-mag. Saturn very low in east and 1.2-mag. Mars within 8° to Saturn’s lower left on May 1. Even though they’re 32° and 24° from Sun, the viewing conditions are very poor, especially from northern states, with the zodiacal belt inclined so low. Use the waning crescent Moon May 13-15 to help find them. By month’s end, these planets are a bit higher and 27° apart. Further enrich your May mornings by utilizing your binoculars and your ears to experience sights and sounds of birds in springtime!
During the hours surrounding its superior conjunction on May 14, Mercury, shining brilliantly at mag. —2.4, will appear on LASCO coronagraph videos of NASA’s Space Weather Prediction Center. Solar conjunction occurs at 7 a.m. PDT (10 a.m. EDT), and Mercury’s disappearance behind the Sun lasts from about 4¼ hours before until 4¼ hours after that time. To view Mercury on NASA’s videos just before and after its 8½-hour occultation by the Sun, visit https://www.swpc.noaa.gov/products/lasco-coronagraph
The near-coincidence of three events -- (1) Mercury passing the ascending node of its orbit and crossing north of the plane of Earth’s orbit on May 13; (2) superior conjunction behind the Sun on May 14; and (3) Mercury’s perihelion, closest to Sun on May 18 -- makes the innermost ascend rapidly and brightly into the post-sunset sky in following days. How soon after May 14 can you spot Mercury just above the WNW horizon shortly after sunset, with optical aid? with unaided eye? (Optically aided sightings – be sure to l
Look after sunset, when Sun’s disk is safely hidden below the horizon -- will be possible by May 20, less than a week after its passage behind the Sun, with Mercury 8° from Sun, and still at shining at mag. –1.6.)
For example, from Palm Springs, CA on May 20, Mercury is 8.0° upper left of the setting Sun and sets 40 minutes after sunset, 24.5° lower right of Venus. On May 21, Mercury is 9.2° upper left of the setting Sun, and sets 45 minutes after sunset, 23.6° lower right of Venus. Remaining above the horizon five minutes longer after sunset is a marked improvement after 24 hours, and it accumulates! By May 24, Mercury is 12.5° from Sun, sets 62 minutes after sundown, and will be easy for unaided eye. By May 31, Mercury, still prominent at mag. –0.6, widens its elongation to nearly 19° from Sun, and follows the Sun over the horizon by more than 1½ hours. Mercury will climb highest in evening twilight in the second week of June, a few days before reaching greatest elongation on the 15th, while 24.5° from Sun, and still visible with unaided eye at mag. +0.4. Later that month, it will drop low in bright twilight and fade from view.
https://skyandtelescope.org/stargazing-and-observing/what-is-a-blue-moon/
You can download a PDF showing and explaining appearance of Saturn's rings over the next 15 years.
Late March/early April is a good time for students to start keeping a checklist of bright stars seen each evening, within the first hour after sunset. Many bright stars are gathered in the western sky, including the huge Winter Hexagon. Striking changes in the visibility of stars will occur in the next several weeks, as a result of the Earth’s revolution around the Sun. Students can list their sightings of planets, and the Moon, too! Use the Daily Skywatch Log provided to record your observations. To include the greatest number of bright stars, begin this activity by mid-April.
Use this chart to track variou stars and planets in the sky.
Are you organizing a star party for a class or assigning individual sky watching projects? We suggest you plan to begin the sessions during evening twilight, so students can experience the joy of discovering and identifying the brighter stars as they first appear. The sessions should begin no later than one-half hour after sunset, or even earlier if you wish to start with telescopic observations of the Moon or bright planets, and conclude after enough dark-sky time for students to observe the deep sky objects on your list.
If you also schedule a predawn session, you might want to allow enough time to observe a selection of stars and deep sky objects before twilight begins. In that case, start the session at least 1¾ to 2 hours before sunrise, and continue long enough into twilight to watch some of the brighter stars disappear.
My friend and former colleague at Michigan State University, Mr. Robert D. Miller, has kindly created computer programs and provided us with monthly sky charts tracking daily locations of the five naked-eye planets and the 15* stars of first magnitude or brighter (*plus Pollux’s twin, Castor, of mag. +1.6 and only 4.5° away) visible from latitude 40° north. Positions of the stars and planets are plotted each day at the moment the Sun is 9° below the horizon, which we have called “mid-twilight”. Locations of the planets are plotted as a separate dot for each day, with larger dots plotted weekly on the 1st, 8th, 15th, 22nd, and 29th day of the month. Star positions during the course of the month are plotted as continuous tracks, with all stars drifting westward (left to right on the charts) in the course of the month, owing to the Earth’s revolution around the Sun.
For latitude 40° N, the moment of evening mid-twilight during the course of the year ranges from 43 to 53 minutes after sunset, and morning mid-twilight occurs at a similar interval ahead of sunrise For locations south of lat. 40° N, the same stage of twilight occurs closer to sunset and sunrise, for example, 39 to 47 minutes after sunset or before sunrise for lat. 34° N.
*On the set of charts for lat. 34° N, another bright star, Canopus, is sometimes visible very low in the south, bringing the visible total to 16 stars of first magnitude or brighter, but not all are seen simultaneously. For locations farther north, twilights are longer.
Sometimes a star is below the horizon at the start of a month, but might appear above the eastern horizon before month’s end, for example Spica low in ESE in evening mid-twilight in late April. On the evening twilight chart for May, Aldebaran, Sirius, and Betelgeuse are low in the western sky at the start of May, but all sink below the horizon in the course of the month.
It is instructive to view the monthly evening twilight charts in order, to follow the seasonal westward drift of the stars. The outer planets Mars, Jupiter, and Saturn,
moving slowly against the stars, are dragged along with the seasonal motion. Outer planets and zodiacal stars Aldebaran, Pollux and Castor, Regulus, Spica, and Antares follow this sequence from beginning to end of an apparition: (1) First appearance, or heliacal rising, on eastern horizon in morning twilight; (2) progress across morning sky over several months from eastern toward western horizon; (3) opposition, when it appears in western sky at dawn and in eastern sky at dusk; (4) progress across evening sky over several months from eastern toward western horizon; (5) last appearance, or heliacal setting, on western horizon during evening twilight.
Stars well north of the zodiac, Capella, Arcturus, and the Summer Triangle of Vega, Altair, and Deneb begin step (1) of the next apparition before finishing step (5) of a current one, for example, Arcturus, 33° N of Sun on October 29, begins to be seen rising in ENE before dawn several days earlier, and remains visible in the western sky at dusk until several days later. A star well south of the zodiac, for example, Sirius, is never up all night, even at opposition on Dec. 31-Jan. 1, when it’s highest in south in middle of night. For several weeks around the opposite time of year, June 30, Sirius is above the horizon only in the daytime and can’t be seen at any time of night.
Mercury and Venus, planets interior to the Earth’s orbit, can never appear at opposition. When they show on the monthly charts, they’re either in the western sky at dusk or eastern sky at dawn. Venus is visible as an “evening star” or “morning star” for seven to eight months at a time. Its sequence is: (1) Superior conjunction, not visible on far side of Sun; (2) first appearance above western horizon at dusk; (3) greatest elongation about 46° from setting Sun, while appearing half full through a telescope. (4) display of crescent phases, ever thinner but larger in apparent size, while sinking back toward western horizon at dusk; (5) inferior conjunction, nearly between Earth and Sun; (6) first appearance above eastern horizon at dawn, beginning display of crescent phases, ever thicker but smaller in apparent size, while climbing toward (7) greatest elongation, about 46° from rising Sun, appearing half full, followed by (8) gradual descent toward last appearance on eastern horizon at dawn, and finally (9) superior conjunction. The duration of a complete cycle of visibility of Venus, including an evening and a morning appearance between superior conjunctions, is nearly 19.2 months, or 5 complete evening-morning cycles in 8 years.
Venus is especially fascinating to watch with binoculars and telescopes in the closing weeks of an evening apparition through the opening weeks of a morning apparition. Venus then passes close to Earth and appears as a large, backlighted crescent in transition between steps (3) and (7), in the sequence described above. The next two transitions, from Venus half full in evening through crescent phases to half full in morning, take place from mid-August 2026 until early January 2027, and from late March until early August 2028.
Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys promoting sky watching to folks of all ages.
| Morning | Evening |
|---|---|
| January | |
| February | February |
| March | March |
| April | April |
| May | May |
| June | June |
| July | July |
| August | August |
| September | September |
| October | October |
| November | November |
| December | December |
Jeffrey Hunt creates annual graphs of evening setting times and morning rising times of Moon, planets and bright zodiacal stars. Both graphs are calculated for Chicago, but are also fairly accurate everywhere within the 48 contiguous United States.
Saturn begins rising before the start of morning twilight by late May 2026, and Mars does so by late June. Mercury has favorable morning appearances in late July-early August, and again in late November-early December. Jupiter emerges into the morning sky by late August. Venus (green curve) quickly emerges as a "morning star" rising ahead of the Sun in late October. By early November, it rises in a dark sky, before the start of twilight, and in mid-December, rises about four hours ahead of the Sun.
In May 2026, Venus (green curve) sets in a dark sky, at its longest time interval after sunset. By mid-October, Venus sets at the same time as the Sun and is no longer visible. Jupiter (yellow curve) appears close to Venus on June 9, and sets during ever brighter twilight later on during June. Mercury has favorable evening appearances during mid-February and again in late May to mid-June. Its appearance in October is much less favorable, since it sets in brighter twilight. Aldebaran sinks into bright twilight during May, and Pollux does so in June.