The Ultimate Guide to Observing Mercury

July 22, 2020

When we talk about our favorite planets to observe through telescopes, which ones most often come to mind? Of course, there's Saturn and its magnificent rings, and Jupiter with its distinct cloud bands, Great Red Spot, and its four brightest moons that can be seen racing around the planet. Then there's Mars, named after the god of war with its reddish battlefield appearance, unique surface markings, and polar ice caps. And finally, there is Venus, Earth's twin (size-wise), which resembles a mini version of our own Moon as it goes through its phases.

But we rarely hear about the planet closest to the Sun—the smallest and most elusive planet in our Solar System—Mercury. Mercury may be one of the least observed planets. Still, it can be safely observed during favorable periods when it reaches its greatest separation from the Sun every few months, placing the planet on either the east or west side of the Sun. Astronomers refer to this as "greatest elongation." Because Mercury is so close to the Sun, elongations occur every few months, placing the planet on either the east or west side of the Sun.

So how do we know when and where to look to find Mercury? Is it dangerous to observe this tiny planet positioned so close to the Sun? What will I see when I view Mercury through a telescope? What should I look for while observing? Here are a few observing tips to help you get better acquainted with our mysterious, rarely seen neighbor.

Tip #1: ONLY attempt to view Mercury during a safe viewing opportunity

Because Mercury never strays too far from the Sun, it's often lost in its glare. Never attempt to locate and observe Mercury in broad daylight or when it lines up with the Sun and Earth at inferior or superior conjunction, as it is extremely dangerous and not worth the risk of accidentally blinding yourself and causing permanent eye damage. Only during a favorable separation from the Sun is it relatively safe enough to observe Mercury in a deep twilight sky when the Sun is below the horizon.

Dates to Observe Mercury in 2022:

  • January 7 – Mercury at Greatest Eastern Elongation
    Mercury reaches greatest eastern elongation of 19.2° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.
  • February 16 – Mercury at Greatest Western Elongation
    Mercury reaches greatest western elongation of 26.3° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the southeastern sky just before sunrise.
  • March 2 – Mercury passes 0.7° south of Saturn
    Look for Mercury to the bottom right of Saturn in the southeastern sky just before sunrise.
  • April 29 – Mercury at Greatest Eastern Elongation
    Mercury reaches greatest eastern elongation of 21° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset. Mercury will set about two hours after sunset by the end of April.  
  • June 16 – Mercury at Greatest Western Elongation
    Mercury reaches greatest western elongation of 23.2° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.
  • August 27 – Mercury at Greatest Eastern Elongation
    Mercury reaches greatest eastern elongation of 27.3° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.
  • October 8 – Mercury at Greatest Western Elongation
    Mercury reaches greatest western elongation of 18° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.
  • December 21 - Mercury at Greatest Eastern Elongation
    Mercury reaches greatest eastern elongation of 20.1° from the Sun. It is an ideal time for viewing Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

 

Tip #2: Use an astronomy app or star chart

Star charts in astronomy-related magazines, books, or websites are visual guides to help you plan your quest to spot Mercury. Today's most modern and informative tools can be found in astronomy apps such as Celestron's SkyPortal mobile app. Simply download this free planetarium app from the Apple App Store or Google Play, and you'll instantly have a wealth of information at your fingertips. SkyPortal provides audio and written descriptions about Mercury; it also provides its celestial coordinates, a real-time sky map, rise and set times, and physical and orbital parameters.

 

Tip #3: The best equipment for viewing Mercury

While it is rewarding to spot Mercury with your naked eyes, a pair of low-powered binoculars can help you locate it as soon as the Sun dips safely below the horizon and the sky begins to fade into twilight. Mercury will be low on the horizon, in a part of the atmosphere that is thicker and more susceptible to atmospheric turbulence. That means Mercury will look like a shimmering or twinkling "star" as it shines through the unstable air.

If possible, use a telescope of at least 2.4" to 4" of aperture, especially one with GoTo and tracking, which will keep Mercury centered for a more stabilized view.

 
 

Tip #4: What to look for while observing Mercury

Because Mercury is an inferior planet whose orbit is closer to the Sun than the Earth's, it displays its phases—viewable only through a telescope—just like a smaller version of our Moon. You'll be able to view Mercury's phases in a small telescope with moderate magnification if seeing conditions are ideal.

Mercury has a reputation for being a challenging telescope target, so it may take a few tries before you're able to observe it. But your patience will pay off; it is the only terrestrial planet other than Mars that reveals some detail on its surface through larger aperture telescopes. However, do not expect to resolve any craters because Mercury is too small.

We hope this brief Mercury viewing guide will be of some help on your mission to observe this elusive little planet in our Solar System. The key is knowing when and where to look. If you wish to learn more about Mercury, please download the SkyPortal mobile app from the App Store or Google Play.

Clear skies!

Other articles you might be interested in: Ultimate Guide to Observing the Universe