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How to See Mercury With A Telescope?

Mercury is the closest planet to the Sun. It orbits the sun every 88 days which means we get several short viewing windows a year. Most of the time it is too close to the sun to observe it. Though it is difficult, you can get an opportunity to view it if you know exactly when and where to look for it. You will be able to see the phases of Mercury, several mountains, and sometimes the craters if you can manage the perfect telescope.

What is Mercury?

Mercury, the smallest planet in our solar system and the closest to the Sun, is a fascinating space object with unique characteristics. It is only slightly larger than Earth’s Moon, with a diameter of 4,879 km (3,032 miles), and its surface is heavily cratered, similar to our Moon. Mercury has the shortest and fastest orbit around the Sun, taking just 88 Earth days to complete one orbit. Its surface temperature experiences dramatic changes, reaching highs of 430°C during the day and dropping to -180°C at night due to the lack of an insulating atmosphere. Mercury has no moons and its thin atmosphere, or exosphere, is composed mainly of oxygen, sodium, hydrogen, helium, and potassium. Despite its small size, Mercury has a relatively large iron core which makes up about 85% of the planet’s volume. Its high orbital eccentricity and lack of axial tilt result in a large temperature range. During the day, the average temperature on Mercury reaches about 427 degrees Celsius (800 degrees Fahrenheit), while at night, it can drop to -170 degrees Celsius (-292 degrees Fahrenheit) due to the absence of an insulating atmosphere. The planet’s tenuous and highly variable atmosphere primarily consists of hydrogen, helium, oxygen, sodium, calcium, potassium, and water vapor, with a combined pressure level of about 1 nPa. The density of Mercury, at 13.534 g/cm³, influences the choice of telescopes for observing its surface details. Mercury’s orbit around the Sun spans approximately 57.9 million kilometers (36 million miles), with an average distance of 57,909,175 km (35,983,095 miles). The planet’s mass is about 3.30 × 10^23 kg, and its diameter measures around 4,880 kilometers (3,032 miles). The major axis of Mercury plays a crucial role in telescope selection, affecting the apparent size and brightness of the planet when viewed from Earth. Mercury’s magnetic field, approximately 1.1% of Earth’s strength, slows down the solar wind and creates a magnetosphere around the planet. The planet’s rotation period is 58.65 Earth days, and its rotational speed is about 10.892 km/h (6.77 mph). The lack of atmosphere on Mercury allows for extreme temperature variations, making it a unique and intriguing object of study in our solar system.

Can you see Mercury with a telescope?

Yes, it is possible to see Mercury with a basic telescope, but a telescope with a larger aperture and higher magnification may be needed for a clearer view. Mercury is approximately 149.6 million kilometers from Earth and can be seen with a telescope, but it may be challenging due to its small size and proximity to the Sun. The prominent surface features of Mercury that can be observed with a telescope include heavily cratered areas, lobe-shaped scarps or cliffs, and Mercury’s “Great Valley.” The three phases of Mercury are the evening apparition phase, the inferior conjunction phase, and the morning apparition phase, and they affect its visibility through a telescope by changing its color and position in the sky. Mercury is difficult to see with the naked eye but can be seen even in the daytime with a telescope if you know where to look. A small disk can be seen when Mercury is close to the Earth, and phases (like the Moon’s) can be seen. The best time to see Mercury is when it’s positioned either farthest west of the Sun in the eastern morning sky or farthest east of the Sun in the evening sky. Be careful when looking for Mercury, as it will always be close to the Sun. While backyard telescopes don’t have enough resolution to fetch details like impact craters and lava fields, there is still so much to look at and enjoy! Mercury races around the sun every 88 days, which means we get several short viewing windows every year. The downside of being so close to the sun is that it is never visible in a truly dark sky – only dawn and dusk – and then only for a few days at a time.

Quick Guide to Observe Mercury

The only time it may be seen an hour after sunset or an hour before sunrise is during a full moon or twilight. Before starting your observation session, check Mercury’s position in the night sky using Mercury Calendar or any other star app. To see it in the morning, turn your head toward the eastern horizon. Try to find it an hour before sunrise because the bright planet will soon be completely obscured by sunlight. You must look toward the western horizon in the evening to see Mercury. You can see Mercury very well via a 50x-magnification telescope with a focal length of 50-70mm.

Before we begin: Choose a star chart or proper astronomy app.

Various astronomy-related books, magazines, and websites provide star charts. Many apps are also now available like Celestron’s SkyPortal mobile app that provides planetary information and real-time sky map. They will help a lot to find the planet, Mercury. Just download the app and write the name on the search option.

How to find Mercury?

  1. Make sure Mercury is in the night sky before your observing session. 
  2. Try to find mercury with your bare eyes. Mercury is in fact white in color. However, its proximity spreads a pinkish hue to the horizon.
  3. Once you get the position of Mercury in the sky, point your telescope towards that direction. Use the finder to center the planet in your main scope. The crosshairs will have to be centered at Mercury too. Now, look through the eyepiece to get the magnified view.

What is the best time to observe Mercury?

Mercury is said to be elusive as it is visible only for a few days every time when it reaches a maximum of 28 degrees away from the sun to the greatest elongation. To view it from the world, the earth needs to go at least 12° away from our sun at that time. It means that a full moon or twilight is the only time when it can be seen an hour after sunset or before sunrise.

Mercury reaches the greatest elongation 7 times this year 2022, alternating between evening and morning skies depending on whether it appears from the east of the Sun or the west.

Windows of the best time to see Mercury:

YearEvening SkyMorning Sky
2022Early Jan, late Apr, late Aug, late DecMid Feb, mid-Jun, early Oct
2023Early AprLate Sep
2024Late MarEarly Sep
2025Early MarMid Aug, early Nov

6 Tips to observe Mercury in the best way:

  • Look for it in the sky at the perfect time of the year according to the star chart.
  • The moon can be your guide if it is in the vicinity of Mercury.
  • Low-power eyepiece is the best to get the clearest view as you will get a wide view of the horizon.
  • Mercury will look like a twinkling star as it appears low on the horizon (10-12 degrees)  where the atmosphere is thicker.
  • During inferior and superior conjunctions, Mercury cannot be seen due to the sun’s glare. Inferior conjunctions occur when Mercury, earth, and the sun are aligned and superior conjunctions happen when mercury is on the opposite side of the sun.
  • Color filters with Wratten Numbers similar to # 21 Orange will reduce the brightness of the sun and improve the viewing experience. 

What can you see on Mercury with a telescope?

  • The phases of Mercury
  • Mountains like the Apennines, Leibnitz Mountains, Caucasus, and Doerfel, etc.

What telescope to see Mercury?

Celestron Inspire 100AZ refractor, Celestron AstroMaster 70AZ, and Sky-Watcher Explorer 130 EQ2 are great telescopes to see Mercury. A list of telescopes to see the planet Mercury has more telescope options that can see Mercury very clearly.

What size telescope to see Mercury?

With a 50-70mm telescope, you will get great views of Mercury. The more the aperture, the better and sharper the views and the details. But to get the best details you should have a telescope with at least 100 mm of aperture.

What magnification is required to see Mercury?

The phases of Mercury can be seen in telescopes at 50x magnification. To see the details, you should use a telescope with at least 100 mm aperture at a magnification of 200-250x.

Enjoying Mercury? Here are other things to see with a telescope.

Mercury is the closest planet front the sun. However, you can observe the other planets of our solar system with the same telescope you use for viewing Mercury. There are thousands of galaxies, nebulae, and star clusters observable with even a small size telescope. Go through the List of things to see with a telescope to learn what other objects are viewable with your telescope and plan for an observation.

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