Mercury hugs the sun so tightly that it can be tricky to see. But April 21 marks its greatest western elongation. This is when the Swift Planet pulls far enough away from the Sun’s glare that it can be clearly seen with the naked eye.
Why April 21 Is the Best Time to Spot Mercury
In the early morning, Mercury will rise before the Sun and hang low in the east close to the horizon as the dawn sky slowly brightens. Elongations like this come along once every 116 days or so, but how easy it is to see Mercury at this point depends on the season and your earthly position.
Observers in the Southern Hemisphere get a better deal this time. Anyone there will be able to spot Mercury after April 10th to the lower right of Venus, which will be shining as brightly as ever. Those in the Northern Hemisphere will be able to start seeing Mercury around April 18th to the lower left of Venus, with the best viewing time 30 to 40 minutes before sunrise.
Saturn will also be nearby, but the Ringed Planet will be dimmer and lower on the horizon. Mercury will be positioned between the two, glowing at a moderately bright magnitude of 0.3 on April 21. While it will continue to brighten in the days that follow, it also sinks lower in the sky, making it increasingly difficult to see as it slips back into the Sun’s glare by late May.
How to See Mercury Safely and Successfully
When the April 18 window opens for stargazers in the Northern Hemisphere, Mercury will appear low in the eastern sky before sunrise. The trick is to have your coffee ready and prepare everything else you need at least 40 minutes before the big orange ball appears.
Never use binoculars or a telescope when the Sun is above the horizon. Even a glimpse can cause permanent damage to your eyes. Stick to viewing with just your eyes unless you are absolutely confident the sunrise is not close.
That narrow morning twilight window is the time when Mercury is perched just high enough above the horizon to be visible to the naked eye. Once the sun starts poking its nose in, the aptly-named Swift Planet makes a rapid exit.
You’ll be able to spot Mercury quite easily by locating Venus, the brightest object in the sky, and looking to its lower left (or lower right in the Southern Hemisphere). You’ll want to boost your chances of a good sighting by finding a spot with an unobstructed view of the low eastern horizon. That means no trees, no buildings, and no hills. Over the ocean or open fields is ideal, but rooftops, balconies, and hillsides also make for much easier spotting. You’ll also benefit from being in a location with clear, crisp morning air and as little light pollution as possible, given that Mercury will be in competition with the growing dawn light.
Why Mercury Is So Elusive
Of all the planets in our solar system, Mercury orbits closest to the Sun. It’s rarely far from it, in fact, which means it is usually obscured by solar glare. Due to this close orbit, Mercury’s viewing windows are brief and usually just before sunrise or shortly after sunset. And this is only when it’s at or close to its greatest elongation.
This close orbit also means Mercury is particularly fast as it moves across the skies. According to Kepler’s Third Law, planets closer to the Sun experience a stronger gravitational pull and must travel faster to stay in orbit. This adds to the brief viewing window, and if you miss it by a few days, you may well miss it altogether.
Additionally, at just over one-third of Earth’s width, Mercury is also the smallest planet in the Solar System. So, even in optimal conditions, it still appears as a tiny point of light. However, these factors add up to Mercury-spotting feeling like a rewarding challenge, at least for casual stargazers who may never have knowingly seen it before.
What Mercury Looks Like Through a Telescope
If you’ve never viewed Mercury through a telescope before, and you’re hoping for the rich surface detail of Jupiter or Saturn, think again. It’s not exactly a showpiece planet. Then again, it’s still worth a look. It appears as a tiny crescent, especially at its greatest elongation. At this time, it’s around 38 percent illuminated and roughly eight arcseconds across. That’s pretty small, so you’ll need to observe in optimal viewing conditions and have a modest telescope at the very least to pick out its details clearly.
Mercury resembles a rather elusive version of our moon. The surface is gray and heavily pockmarked by craters and scarred by the impacts of ancient asteroids and comets. It also looks very stark, which is largely down to its (almost) complete lack of atmosphere. There’s nothing to scatter the sunlight or create any haze, meaning shadow areas on Mercury are sharp and deep while surface details are unfiltered, very much like how things look on the Moon.
There are also no clouds, color, or movement. It’s basically a static rock. However, this is the appeal of viewing Mercury. Basically, through a telescope, you’re seeing our solar system’s innermost world in all its barren reality.
Other Mercury Sky Dates to Watch in 2025
2025 is a busy year for Mercury, with seven elongations taking place against the usual six. In addition to April 21’s greatest western elongation, here are some other significant Mercury dates to watch out for throughout the year.
May 30, 2025 – Superior Conjunction
On May 30, Mercury will pass behind the Sun from our point of view on Earth. This event is known as a superior conjunction and marks the end of its morning visibility phase following April’s greatest western elongation. The Sun’s glare will completely obscure the planet, and it can no longer be observed.
July 4, 2025 – Greatest Eastern Elongation
On this day, Mercury will reach its greatest eastern elongation. This means it will be at its farthest apparent distance from the Sun in the evening sky. It also means those in the Northern Hemisphere won’t have to get out of bed early to view it. So, if you’re not an early riser and can wait a couple of months, you can see it after sunset when it is far enough from the Sun’s glow to appear in the twilight sky at dusk. This is also when Northern Hemisphere stargazers get their chance to view Mercury for an extended schedule.
July 31, 2025 – Inferior Conjunction
On this day, Mercury will move between the Earth and the Sun. This is called an inferior conjunction. At this point, the planet is, once again, unobservable. Mercury will now continue on its way and reappear on the morning side of the sky at its next elongation.
After this point, Mercury continues its regular cycle of conjunctions and elongations, alternating between the morning and evening sky. Each event will bring slightly different viewing conditions depending on your location. But overall, the pattern remains familiar. Here are the remaining dates for 2025:
- August 19, 2025 – greatest western elongation
- September 13, 2025 – superior conjunction
- October 29, 2025 – greatest eastern elongation
- November 20, 2025 – inferior conjunction
- December 7, 2025 – greatest western elongation
So, Mercury isn’t really that hard to see. However, it can be easy to overlook. It does appear in plain sight several times a year, yet most of us don’t even realize it. That’s what makes spotting Mercury rewarding, especially if you can catch its tiny crescent through a telescope. Mercury isn’t rare; it’s just rarely noticed.
Take a look up this April 21st and impress your friends, or get a detailed look through a telescope and admire its Moon-like appearance. Just ensure the sun is well below the horizon before using any magnifying tools.
