Clocks Spring Forward, Mercury at Maximum Under Venus, and the Moon Manifests an X and Much More in Evening!
This image of the Lunar Straight Wall or Rupes Recta in Mare Nubium was captured by the Lunar Reconnaissance Orbiter. While the feature can be seen through binoculars, a backyard telescope will reveal more detail. (Adapted from NASA LRO)
Hello, March Stargazers!
Here are your Astronomy Skylights for the week of March 2nd, 2025 by Chris Vaughan. Feel free to pass this along to your friends and send me your comments, questions, and suggested topics. You can also follow me on FaceBook, Instagram, Threads, and Bluesky as astrogeoguy! Unless otherwise noted, all times are expressed in Eastern Time. To subscribe to these emails please click this MailChimp link.
If you’d like me to bring my Digital Starlab portable inflatable planetarium to your school or other daytime or evening event in Simcoe, Grey, and Bruce Counties, or deliver a virtual session anywhere, contact me through AstroGeo.ca, and we’ll tour the Universe, or the Earth’s interior, together! My book with John A. Read entitled 110 Things to See With a Telescope is a guide to viewing the deep sky objects in the Messier List – for both beginners and seasoned astronomers. DM me to order a signed copy!
Clocks change next weekend. The moon will grace the evening sky all week, so I highlight what to look for each night, including some lunar letters to see on Thursday only. The inner planets gleam in the west at dusk, three more shine all evening, and Jupiter sports spots. Read on for your Skylights!
Springing Forward
For jurisdictions that employ Daylight Saving Time (or DST, for short), clocks should be set forward by one hour at 2 am local time next Sunday morning, March 9. In North America, the “Spring Forward” will remain in effect until Daylight Saving Time reverts to Standard Time when we “Fall Back” on November 2, 2025.
Nowadays, our phones and more modern appliances do that automatically. Here’s the idea behind it.
For most of human history, people woke with the sun and went to bed at dusk. At equatorial latitudes, where most of humanity lived, hunted, and farmed, the number of hours of daylight through the year didn’t vary too much – so that approach worked well. But, as communities spread around the world and began to use standardized working hours – especially at latitudes farther from the equator where the days lengthened and shortened dramatically throughout the year – people were forced to use artificial light indoors when the sun wasn’t shining into windows or through skylights.
Scientist/naturalist Benjamin Franklin, in a satire he published while living in Paris in 1784, proposed that Parisians get out of bed earlier to take advantage of the early sunrises in summer – and thereby save money on candles and oil in evening by retiring early. For the same reason, during the 19th Century it became common for schools and businesses to adjust their operating hours with the seasons – but that practice wasn’t standardized.
New Zealand entomologist George Hudson first proposed what became Daylight Saving Time in 1895 – but he wanted the clocks changed by 2 hours! The idea then spread to England where prominent English builder and outdoorsman William Willett, who was also an avid golfer, noted that more work (and golf) could be fit into the day if the clocks were advanced during the warm months of the year.
While the British parliament toyed with the concept for years, it was Canada that led the way on Daylight Saving Time! The first city in the world to enact DST, on July 1, 1908, was Port Arthur, Ontario, Canada – followed soon after by Orillia, Ontario. The German Empire and Austria-Hungary adopted DST on April 30, 1916 as a way to conserve coal during World War I. Britain and most of its allies, plus many European neutral countries soon followed. The USA adopted DST in 1918. Other than in Canada, the UK, France, Ireland, and the United States, DST was abandoned after the war; but it was re-instated during World War II and then widely adopted as a result of the energy crisis of the 1970’s.
The inconvenience of twice-yearly clock changes has led to calls to abandon the practice. Some jurisdictions, including Ontario, Canada and the USA, have proposed to remain on DST year-round. But the proposals that have passed various legislative bodies require the adjoining jurisdictions (New York state and Quebec in the case of Ontario) to make the change, too.
I’d prefer to remain on Standard Time year-round and adjust school and office hours where necessary. For stargazers, advancing clocks by one hour, plus the fact that sunset occurs 1 minute later with each passing day near the March equinox, means that spring and summer star parties and dark-sky observing cannot begin until much later in the evening – usually after the bedtime of the junior astronomers! Staying on DST will also mean that existing sundials will be permanently wrong because solar noon will always occur at 1 pm, and not at 12 pm.
The names and abbreviations for our time zones change when DST is in effect. Eastern Standard Time (EST) becomes Eastern Daylight Time (EDT), and so on. For those who deal with the timing of astronomical events, the difference between your local time and the international standard of Greenwich Mean Time (or GMT) and the astronomers’ Universal Time (UT), is reduced by one hour when DST is in effect. Between March and November, clocks in the Eastern Time zone subtract 4 hours from GMT. For the rest of the year it’s 5 hours. (I do that math for you in these Skylights!)
One final thought. Where time zones are broad, they cover many degrees of longitude. For people living there, despite sharing the same time on the clock, the sunrise and sunset times can be radically different for locations on the eastern and western edges of their zone. The Eastern Time zone covers nearly two hours’ worth of longitude at the latitude of Ontario and Quebec! If you want your summer sunsets to occur at the latest possible time, you need to live in the western part of your time zone. If you prefer more daylight in the early morning, then live as far to the east in your time zone as possible. Trevor Kjorlien of Plateau Astro explained it very well on his YouTube channel here.
The Moon’s Just Going through a Phase
The moon will be ideally situated for viewing in the evening this week. The moon takes 29.5 days to repeat its phases – its synodic period. Let’s just call that a lunar month – notice how that word and the word “moon” are cousins? During the two weeks that it takes to transition from new moon to full moon (half the lunar month), our natural satellite is swinging steadily eastward away from the sun – by about its own diameter every hour, or by about 12° of sky per day. (If you extend your arm upwards and close one eye, your closed fist will cover about 10° of the sky. Stick your thumb knuckle out a bit to cover 12°. This trick works for both adults and kids.)
A day or so after new moon, we see its pretty, slender crescent following the sun down in the west. As each day passes, the moon’s extra 12° angle from the sun delays its setting time, eventually allowing it to shine in a dark sky with the stars and planets. At new moon, sunlight can only reach the far side of the moon. As it slides east away from the sun, the moon’s sunlit hemisphere rotates more and more into view of Earthlings, causing the illuminated phase of the moon to increase. A week after its new phase, the moon has completed one quarter of its orbit and shines half-illuminated in the evening sky.
The circle that separates the lit hemisphere from the dark hemisphere on the moon is called the terminator. It also passes through the moon’s north and south poles. The terminator migrates steadily across the moon from lunar east to lunar west when the moon is waxing in phase. From new to almost first quarter, the terminator is curved and the lit part of the moon shows a crescent shape. At first quarter, the terminator becomes a straight line. For the week leading to the full moon, the terminator curves increasingly the opposite way and the lit part of the moon is gibbous. That obvious pattern told ancient sky-watchers that the moon was a sphere.
During the other half of the lunar month, from full moon to new moon, the moon is swinging toward the sun again and waning in illuminated phase. The terminator changes the same way, but now the dark hemisphere is the one rotating more toward Earth. For the second half of the lunar month, the moon rises after midnight and sets during the morning daytime – so you won’t see the moon in evening, but you might see it in daylight on the way to work or school.
Okay – with all that out of the way, let’s talk about why that matters. Standing anywhere along the terminator on the waxing evening moon, an astronaut would see the sun rising. When you witness sunrise or sunset on Earth, it’s because Earth’s own terminator is sweeping over you! Sunrise light rays are horizontal. They cast long shadows from mountain peaks, crater rims, ridges, and boulders, and leave even shallow depressions appearing as pools of inky blackness. Low angled illumination also accentuates subtle lunar features like minor fault scarps and the ripples from lava floods that cooled while flowing.
Magnified views of the terrain near the lunar terminator are breath-taking. A small backyard telescope or a pair of binoculars will suffice. Since the terminator is constantly moving, new vistas are enhanced every hour and night over night. Pick a location and watch the shadow lengths change or a crater gradually transition from fully dark to half-lit to fully exposed. You can even judge how deep or how tall the features are. Have your gear ready to take a peek at the moon on every clear night this week. Here’s what to watch for…
Tonight (Sunday) after sunset, the pretty, slim crescent moon will pose to the upper left of the brilliant planet Venus. Watch for reflected Earthshine slightly brightening the rest of the moon’s disk and the very obvious grey oval of Mare Crisium “the Sea of Crises” snuggled within the moon’s lit crescent. Once the sky darkens, the stars of Pisces (the Fishes) will emerge around the moon and Venus.
On Monday night the thicker crescent will expand to include dark Mare Fecunditatis “the Sea of Fertility” and plenty of craters along the terminator to its left (or lunar south). The moon will be much higher than Venus and the bright stars of Aries (the Ram), Hamal and Sheratan will shine to the moon’s right (or celestial north).
Tuesday night will add Mare Tranquillitatis “the Sea of Tranquility” and much smaller Mare Nectaris “the Sea of Nectar”. A large crater named Theophilus will be a dark pool above Mare Nectaris. Mare Tranquillitatis appears darker and bluer than the other “seas” due to its enrichment in the mineral titanium. That’s one of the reasons Apollo 11 was sent there.
On Wednesday evening after dusk, the nearly half-illuminated moon will shine to the lower right (or celestial northwest) of the brilliant planet Jupiter. The bright little Pleiades Star Cluster, which is best viewed in binoculars, will be positioned about a palm’s width below the moon. Those viewing the trio later, or in more westerly time zones, will see the moon shifted closer to Jupiter and farther from the cluster. The northern portion of the moon will show large Mare Serenitatis “the Sea of Serenity” bisected by the terminator. Theophilus will now be fully lit.
The moon will complete the first quarter of its orbit around Earth, measuring from the previous new moon, on Thursday, March 6 at 11:32 am EST or 8:32 am PST or 16:32 Greenwich Mean Time. At first quarter, the 90 degree angle formed by the Earth, sun, and moon will cause us to see our natural satellite as a half-moon with its right-hand (eastern) hemisphere illuminated. At this part of the lunar cycle, the moon always rises around noon and sets around midnight, allowing it to be seen in the afternoon daytime sky, too.
After dusk on Thursday evening, the bright star Elnath, which marks the northern horn-tip of Taurus (the Bull), will shine just to the moon’s upper left. Depending on your time zone, you may see the moon farther from it or extremely close to that star, which also completes the large oval of Auriga (the Charioteer). All of Mare Serenitatis will be then lit up, and also smaller Mare Vaporum “the Sea of Vapours” to its left and a bit of huge Mare Imbrium “the Sea of Showers” above it. But wait, there’s more!
Several times a year, for a few hours near its first quarter phase, a feature on the moon called the Lunar X becomes visible in powerful, tripod-mounted binoculars and through any size of backyard telescope. When the rims of the craters Purbach, la Caille, and Blanchinus are illuminated from a particular angle by the sun, they form a small, but very obvious X-shape. The phenomenon is an example of pareidolia – the tendency of the human mind to see familiar objects when looking at random patterns. The Lunar X is located near the terminator, about one third of the way up from the southern pole of the moon (at lunar coordinates 2° East, 24° South). A prominent, round crater named Werner sits to its lower right (or lunar southeast).
On Thursday evening, March 6, North Americans with clear skies can see the Lunar X. The ‘X’ is predicted to start developing around 6 pm EST (or 18:00 Greenwich Mean Time), while the sky is still darkening. When the sun’s light first touches the crater rims, the X will be indistinct. The shape will intensify until around 7:30 pm EST (or 00:30 GMT), in a dark sky for the Eastern Time Zone. It will become less distinct and disappear around 9 pm EST (or 02:00 GMT). This Lunar X will be visible from anywhere on Earth where the moon is shining, especially in a dark sky, during those hours.
During a Lunar X event, you can also look for the Lunar V and the Lunar L on the moon. The “V” is produced by combining the small crater named Ukert with some ridges to the east and west of it. It is located a short distance above the moon’s equator at lunar coordinates 1.5° East, 8° North. For a further challenge, see if you can see the letter “L” down near the moon’s southern pole. Its position is to the southwest of three prominent and adjoining craters named Licetus, Cuvier, and Heraclitus which, in combination, resemble Mickey Mouse’s head and ears.
During 2025, there will be two excellent Lunar X events for the Eastern Time Zone – in evening on May 4 and Dec 26 – plus five more daytime or twilight occurrences. Observers in other time zones will have their own Lunar X events. Here is a list of the start times for Lunar X events during the rest of this year, rounded to the nearest 5 minutes. I’ve also listed local times and notes for the Eastern Time Zone. If the GMT time converts to late afternoon or evening in your own local time zone, mark your calendar!
Date Start Time Local Start Time Notes for Eastern Time Zone
Mar 6, 2025 22:55 GMT 5:55 pm EST (twilit sky)
Apr 5, 2025 12:45 GMT 8:45 am EDT (below the horizon)
May 5, 2025 01:35 GMT 9:35 pm EDT on May 4 (excellent!)
Jun 3, 2025 13:20 GMT 9:20 am EDT (below the horizon)
Jul 3, 2025 00:15 GMT 8:15 pm EDT on Jul 2 (darkening sky)
Aug 1, 2025 10:45 GMT 6:45 am EDT (below the horizon)
Aug 30, 2025 21:25 GMT 5:25 pm EDT (twilit sky)
Sep 29, 2025 08:45 GMT 4:45 am EDT (below the horizon)
Oct 28, 2025 21:10 GMT 5:10 pm EDT (twilit sky)
Nov 27, 2025 10:45 GMT 5:45 am EST (below the horizon)
Dec 27, 2025 01:25 GMT 8:25 pm EST on Dec 26 (best one of the year!)
On Friday night the gibbous moon will shine to the lower right of reddish Mars and the stars of Gemini (the Twins). Enjoy the dramatic curved mountains ringing Mare Imbrium and Rupes Recta, also known as the Lunar Straight Wall, a feature that is very obvious in good binoculars and backyard telescopes. The rupes, Latin for “cliff”, is a north-south aligned fault scarp that extends for 110 km across the southeastern part of Mare Nubium “the Sea of Clouds”, which sits in the lower third of the moon’s Earth-facing hemisphere. The feature is always prominent a day after first quarter and day before last quarter.
Once the sky darkens on Saturday evening, bright reddish Mars and Gemini’s two brightest stars Castor and Pollux will form a triangle around the bright gibbous moon. Mars and the moon will be close enough together to share the view in a backyard telescope or binoculars. The “twin” stars will shine off to their left (or celestial northeast). As the night wears on the moon’s eastward orbital motion will carry it between Mars and Pollux and the diurnal rotation of the sky will move the twins to above the moon and Mars. Much more of Mare Imbrium will be visible, as well as the big crater Copernicus below it and raggedy dark Mare Nubium “the Sea of Clouds” below that. My favorite crater Clavius, famous from the film 2001: A Space Odyssey and its arc of size-changing craterlets, will be highlighted near the terminator below Mare Nubium.
We end the week with the bright, 83%-illuminated moon hiding the faint stars of Cancer (the Crab) around it next Sunday night. The eastern part of the dark expanse of Oceanus Procellarum “the Sea of Storms” will spread along the moon’s left-hand side.
The lunar terminator will fall across the western edge of Sinus Iridum, the Bay of Rainbows. The circular, 249 km-wide feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its right (lunar east) – forming a rounded “handle” on the western edge of that mare. A claire-obscure effect called the “Golden Handle” effect is produced when the rising sun lights up the peaks of the prominent curving Montes Jura mountain range surrounding Sinus Iridum on the north and west, while the floor of the bay at their feet remains unlit. Watch for the promontories named Heraclides and Laplace that poke into Mare Imbrium to the south and north of the bay, respectively. Any telescope will show you that Sinus Iridum is almost craterless – so we know that it is geologically young. But it does host a set of northeast-oriented dorsae or “wrinkle ridges” that are nicely revealed at this lunar phase.
The Planets
At long last, I think the astronomers’ nightmare may be over! The breathless, over-the-top social media posts and totally misleading pictures about seeing every planet should now fade into obscurity. We still have five planets that are easy to see every evening, though.
Starting over in the west after sunset, Mercury is deep into a good evening appearance that will last until mid-March. The planet will move a little more away from the sun every day until Saturday, causing it to linger a bit longer after sunset and climb a bit higher in the western sky. On Saturday, March 8, Mercury will stretch to its widest separation of 18.1° east of the sun, and also its maximum visibility for its current apparition. You can start to look for Mercury at about 6:30 pm local time. It will set by about 7:45 pm, so 7 pm is optimal for seeing it. The planet is relatively bright now, allowing you to see it with your unaided eyes and through binoculars – but use them only after the sun has completely set. If you are able to see Mercury in your telescope, it will have a gibbous, rugby ball shape that will wane in illuminated phase over the week. The thick atmosphere over the western horizon will cause Mercury to look hazy and shaky in a telescope.
While Mercury is moving away from the sun, slower Venus is dropping towards our star a little more every night. For those into astrology, Mercury is moving prograde while Venus is in retrograde. Venus is still shining near its maximum brilliance in the west as the sky darkens ahead of sunset. It will rapidly drop lower over the next two weeks and depart when Mercury does, so enjoy it while you still can. This week, Venus will drop into the trees by about 7:45 pm local time. To see the planet’s large, but extremely slim crescent most clearly, wait until the sun has fully set and then aim your telescope at Venus while the sky is still bright. That way Venus will be higher, shining through less intervening air, and her glare will be lessened. Good binoculars can hint at Venus’ non-round shape, too. Some people claim to be able to see Venus’ crescent without optical aid. Try it! Edgar Allen Poe described seeing a crescent Venus (“Astarte”) in his poem Ulalume, published in 1847. As I mentioned above, the young crescent moon will make a pretty sight above Venus tonight.
Like Venus, very bright, white Jupiter will become visible high in the southern sky around sunset. Medium-bright, reddish Mars, which is located 3.5 fist diameters to the left (or celestial east) of Jupiter, won’t emerge until the sky darkens a bit more.
Jupiter will descend the western sky and then set around 2 am local time. This month, Jupiter will shine above Taurus’ brightest star, reddish Aldebaran, which marks the eye of the bull. The rest of the bull’s triangular face, composed of a group of farther-away, medium-bright whitish stars named the Hyades Cluster, will be sprinkled to the right of Aldebaran. Binoculars will reveal that many are close-together star pairs.
The more concentrated, brighter star cluster named the Pleiades, the Seven Sisters, or Messier 45 is located a fist’s diameter to the upper right of Jupiter and Aldebaran. It’s easy to see with your unaided eyes, but it, too, looks particularly nice in binoculars. If you view it before the sky fully darkens, you’ll be able to count the seven sisters. Their parent stars Atlas and Pleione will be huddled together to the girls’ upper left.
Uranus is located a palm’s width below the Pleiades this month. The distant ice giant planet will be observable from the end of evening twilight until about 11 pm, when it will be hitting the treetops in the west. Uranus can be seen with unaided eyes if you know where to look. If you use your binoculars to find the up-down pair of medium-bright stars named Botein and Al Butain IV (aka Epsilon Arietis), Uranus will be the dull-looking blue-green “star” located several finger widths to their left (or southeast). In a backyard telescope, Uranus will appear as a fairly prominent, non-twinkling blue-green dot.
Viewed in any size of telescope, Jupiter will display a large disk striped with brownish dark belts and creamy light zones, both aligned parallel to its equator. With a better grade of optics, Jupiter’s Great Red Spot, a cyclonic storm that has raged for hundreds of years, becomes visible for several hours when it crosses the planet every 2nd or 3rd night. For observers in the Americas, that GRS will cross Jupiter’s disk during early evening on Tuesday (with two black shadows!), Thursday, and next Sunday, and also after 10 pm Eastern time on Monday, Wednesday, and Saturday night. If you have any coloured filters or nebula filters for your telescope, try enhancing the spot with them.
Any size of binoculars will show you Jupiter’s four Galilean moons named Io, Europa, Ganymede, and Callisto lined up beside the planet. Those moons complete orbits of the planet every 1.7, 3.6, 7.2, and 16.7 days, respectively. If you see fewer than four moons, then one or more of them is crossing in front of or behind Jupiter, or hiding in Jupiter’s dark shadow – or two of the moons are very close together, or one moon is eclipsing or occulting another one.
From time to time, observers with good quality telescopes can watch the black shadows of the Galilean moons travel across Jupiter’s disk. In the Americas, Io’s small shadow will follow the Great Red Spot across Jupiter on Monday evening, March 3 between 10:02 pm and 12:12 am EST (or 03:02 to 05:12 GMT on Tuesday). On Tuesday evening, March 4, observers located in the eastern Americas get a treat when two of the shadows and the Great Red Spot crossing the southern hemisphere of Jupiter together for about 90 minutes. At 6:36 pm Eastern Time (or 23:36 GMT), the small shadow of Europa will join the red spot and the much larger shadow of Ganymede, which began its own crossing of the planet’s south polar zone 55 minutes earlier. Ganymede’s shadow and the spot will leave Jupiter at 8:04 pm EST (or 01:04 GMT on Wednesday), leaving Europa’s shadow to continue on alone until 9:10 pm EST. Additional shadow crossings will be visible in other time zones.
Mars is the last planet to rise and to set, so it’s at the tail end of the planet parade. Its medium-bright, reddish dot will shine high in the southeastern sky after dusk, forming a triangle to the right (or celestial southwest) of Gemini’s bright stars Pollux and Castor. Mars will be highest due south at 8:45 pm local time and set in the northwest before 5 am local time.
At 136 million km away and receding every night, Mars is still close enough to Earth to show us its bright polar cap and some dark patches on its small reddish globe when viewed through a quality backyard telescope. Those features will be less distinct with each passing week as the planet shrinks in size and rapidly fades in brightness while Earth moves farther and farther from it. We can continue to observe Mars as a bright dot until late July, but do your close-up viewing now.
Walking the Big Dog
If you missed last week’s tour of the constellation of Canis Major (the Big Dog), I posted it with sky charts and pictures here.
Public Astronomy-Themed Events
Every Monday evening, York University’s Allan I. Carswell Observatory runs an online star party – broadcasting views from four telescopes/cameras, answering viewer questions, and taking requests! Details are here. They host in-person viewing on the first clear Wednesday night each month. Other Wednesdays they stream views online via the observatory YouTube channel. Details are here.
On Wednesday evening, March 5 at 7:30 pm EDT, the RASC Toronto Centre will host their free, public Recreational Astronomy Night Meeting at the Petrie Science building at York University and also live streamed at https://www.youtube.com/rasctoronto/live. Talks will include The Sky This Month, the aurora borealis, and observing projects. Details are here.
On Thursday, March 6, starting at 7 pm EDT, U of T’s AstroTour at McLennan Physical Laboratories, 60 St George St., Toronto, will present a free public lecture by U of T Graduate Student Michael Poon. His talk will be Seasons Across the Universe. The talk will be followed by astronomy demos and telescope tours (weather permitting). Details are at https://uoft.me/astrotours.
On Saturday, March 8 from 2 to 4 pm, RASC Toronto Centre will host “Space Action: Craters and Comets” at the David Dunlap Observatory for visitors aged 5 and up. This program runs rain or shine. Details and the link for tickets is available at ActiveRH.
Keep your eye on the skies! I love getting questions and requests. Send me some!