Planets and astronomy captured my interest at an early age. It began 75 years ago, when I was in sixth-grade, in the 1950-51 school year.
My science teacher had our class do a huge mural of the solar system, showing the planets’ relative sizes and distances from the sun. Our then-rural Long Island, N.Y., school district had no schools serving students beyond the sixth-grade, so in the following years, I attended secondary school in a neighboring district. I thank my lucky stars—literally—that the school librarian kept some timeless, inspiring books on the shelves. The Friendly Stars, by Martha Evans Martin, published in 1907, associated the delicate blue hepatica wildflowers blooming in the early spring with April’s arrival of the similarly colored star Vega above the northeast horizon. Another early favorite of mine was A Dipper Full of Stars: A Beginner’s Guide to the Heavens, by Lou Williams Page (published in 1944, part of the old California State Series of textbooks for students). It helped me find my way around the sky, with techniques I still employ today to introduce newcomers to the beauty of the night sky.
By nightfall at the start of April each year, there is a huge collection of bright stars in the western half of the sky. It includes seven stars of first magnitude or brighter, nearly half the total of 15 such stars visible over the course of the year from the latitude of Reno.
During evenings in April 2025, there are two bright planets visible. The departure of Venus has left Jupiter, in the west at dusk, as the brightest evening “star.” Mars is high in the southern sky in evening twilight as the month begins, not far from the noticeably fainter “Twin” stars of Gemini, Pollux and Castor.
The bright stars in the western half of the sky are arranged in a huge oval, sometimes called the Winter Hexagon, or Winter Ellipse. Its brightest star, not as bright as Jupiter, is Sirius, the Dog Star, in the south-southwest. Going clockwise around the oval, we encounter Procyon, the brightest star in Canis Minor, the Little Dog. Next, in quick succession, we find Mars, Pollux and Castor. (Castor, of magnitude +1.6, doesn’t quite make the cut as a first-magnitude star.) Next, high in the northwestern sky, we find Capella, the “Mother Goat” star, the second-brightest and northernmost star of the oval, a distant 66° from Sirius. The next star, below brilliant Jupiter, is Aldebaran, eye of Taurus, the Bull, and “follower” of the Pleiades star cluster nearly 14° to its lower right. The last star in the oval is Rigel, Orion’s foot. Note the striking row of three second-magnitude stars, the belt of Orion, above Rigel, and the reddish supergiant star Betelgeuse, above the belt and inside the oval.
There are four additional bright stars visible in the eastern half of the sky before any of the bright stars in the western sky drop below the horizon. The Big Dipper in the northeast can help locate three of these. Extend the familiar line of the Pointer stars backward, away from the North Star, to find Leo, the Lion, with its brightest star, Regulus, high in the southeast. Extend the curve of the Big Dipper’s handle into the eastern sky to “follow the arc to Arcturus and drive a spike to Spica.” The last star to appear before Rigel sets south of west is Vega, rising in the northeast after nightfall for much of April. Once Vega has risen, 11 stars of first magnitude or brighter are visible simultaneously, or 13 objects if you include the two planets!
The stars will return to these same positions in the sky a year from now at the same time of night, owing to the revolution of the Earth around the sun—but the moon and the planets perform differently from one year to another. On the first evening of April, we find Mars 4.1° south of Pollux on a line toward Procyon, and we find Jupiter nearly 8° above Aldebaran, and nearly on a line toward 1.7-magnitude Elnath, tip of the Bull’s northern horn. Planets caught the attention of folks long ago because of their changing position against background stars. The sun and moon were once considered planets, too.
On the evening of April 1, the 19 percent crescent moon appears 3° above the Pleiades cluster. On the next evening, the 29 percent crescent will pass 5° north of Jupiter. At dusk on April 4, the moon will be at first quarter phase, half full, and 90°, or a quarter-circle, east of the sun. On the evening of April 5, the 61 -percent gibbous moon is 4° east of Mars and forms a compact gathering with Mars and Pollux.
On April 7 and 8, the waxing gibbous moon skips past Regulus, moving from west to east of the star on consecutive nights. On the evening of April 11, the 99 percent moon is 10° to the upper right of Spica. On April 12, the evening of the full moon, our natural satellite appears 1°-2° to the lower right of Spica. Although we can’t observe the sun’s position directly against background stars, we know tonight the sun is almost directly opposite the star Spica, which lies in opposition to the sun on April 13 and is visible all night. As seasons pass, the stars opposite to the direction of the sun change, too. The sun is in opposition to Spica on April 13, and to Antares on the night of May 30, when Antares will be visible all night from dusk to dawn, and the sun will be in conjunction with the star Aldebaran. Before the end of May, we’ll lose sight of Aldebaran in the western twilight glow.
Pay close attention to the positions of Mars and Jupiter against background stars, and over time, changes will be obvious. This month, Mars goes east 0.3° to nearly 0.5° per day, while Jupiter progresses 0.16° to 0.20° daily. Binoculars will enhance your views. On April 1, Mars is 4.1° south of Pollux on a line toward Procyon. On April 10, Castor, Pollux and Mars will lie in a straight line. A week later, on April 17, Mars will be equidistant from Pollux and the Beehive star cluster.
See the morning mid-twilight sky map depicting the sky when the sun is 9° below the east-northeast horizon. By far, the sky’s most dominant feature is the planet Venus, shining at magnitude -4.3 to -4.8, reaching peak brilliance on April 22, but with barely a change for a week before and after. Venus shows a crescent, resolvable even in binoculars, 4 percent full and 57 arcseconds across on April 1, filling out to 28 percent and shrinking to 37 arcseconds across by April 30.
Also noteworthy is Saturn, appearing ringless, because Earth passed through the plane of the rings on March 23, and we have since been observing the unlit south face of the rings, until Saturn’s autumnal equinox on May 6, when the sun will cross to the south side of the ring plane, and we’ll start seeing illumination on the side of the rings tipped toward us. But conditions are quite unfavorable for getting detailed telescopic views of Saturn, because with the southernmost zodiac constellations low in the south before sunrise, planets appearing near the sun, like Saturn and Mercury this month, appear low in bright twilight. Using optical aid, especially early in month, look for Saturn to the lower right of Venus, by nearly 9° on April 3; 8° on April 6; 7° on April 11; 6° on April 16; 4° on April 25; and a minimum of 3.7° when these planets appear closest to each other on April 28 and 29.
Mercury, unlike Venus, has no cloud cover, and it appears quite dim when in crescent phase early in its morning apparitions. Mercury attains magnitude +1.0 on April 10, when it’s 6.5° to the lower right of Venus and 2° left of slightly fainter 1.2-magnitude Saturn. Despite Mercury reaching its greatest angular distance for this year, 27°, on April 21, Mercury reaches its greatest altitude of only 1.6° up in mid-twilight in Reno from April 14-20. This is the worst morning apparition of Mercury this year for northern hemisphere sky-watchers. After April 10, Mercury appears increasingly farther to the lower left of Saturn, by 2.9° on April 14; 3.9° on April 16; 5.9° on April 19; 10° on April 24; and 17° on April 30, when Mercury has brightened to magnitude +0.1.
The waning moon in the morning sky appears near Spica on April 13. The moon occults the star Pi in the head of Scorpius in the early morning of April 16, from 12:35 to 1:55 a.m. in Reno. Later, as morning twilight brightens, find Antares, heart of the Scorpion, to the upper left of moon. On April 17, Antares will appear to the right of the moon. On April 18, an unusually low, southern moon reaches its high point in the south only 21° up, 70 minutes before sunrise in Reno.
On April 24, the 15 percent crescent moon is 9° to the upper right of Venus. On April 25, the 6 percent moon is surrounded by three planets! They are Venus and Saturn, about 6.5° to the moon’s upper right, and Mercury, about 5.5° to the moon’s lower right. Neptune’s in there, too, within 3° to the upper right of the moon, but twilight is just too much for the eighth-magnitude planet. One last morning chance for the moon: On the 26th, in bright twilight half an hour before sun-up, try for the 3 percent crescent 21° to the lower left of Venus, and 10° to the lower left of Mercury.
New moon occurs on April 27 at 12:31 p.m., so the moon can’t be seen on that date. The moon will appear in the west-northwest in Taurus the next three evenings, in very favorable view. In twilight about an hour after sunset on April 28, the 3 percent crescent moon with beautiful earthshine on its dark, non-sunlit upper side will be 3° to the lower right of the Pleiades. The view will be spectacular through binoculars! On the 29th, the 8 percent moon will form an isosceles triangle with Jupiter and Aldebaran, 10° from each. Jupiter is then 12° above Aldebaran. On the 30th, the 16 percent crescent will appear 7° to the upper right of bright Jupiter, and 4° to the upper left of Elnath, northern horn of the Bull.
These events, and other gatherings of the moon, planets and stars, are illustrated on the Abrams Planetarium Sky Calendar. For $12 per year, subscribers receive quarterly mailings, each containing three monthly issues; learn more at www.abramsplanetarium.org/skycalendar.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still helps produce an occasional issue. He enjoys being outdoors sharing the beauty of the night sky and other wonders of nature. Robert Miller, who provided the evening and morning twilight 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.
Updated on April 11 to correct a minor error.
