A universe of discovery: what can you see with a 100mm telescope

What can you see with a 100mm telescope? Ever wonder what’s out there in the sky but think you need an expensive, high-powered telescope to see anything interesting?

Think again. Even with a small 100mm telescope, a whole universe of discovery is within your reach.

You don’t need to be an astronomer to unlock the secrets of the cosmos – just a little curiosity and patience. Point your 100mm scope at the night sky and prepare to be amazed at what unfolds before your eyes.

Faraway galaxies, nebulae glowing in vivid colors, craters on the moon, the rings of Saturn, and other deep sky objects – all this and more can be glimpsed through the telescope lens of a modest but mighty 100mm telescope.

what can you see with a 100mm telescope
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Using a 100mm telescope for stargazing

A 100mm telescope may be small, but it can reveal some spectacular sights in the night sky. Here are some of the celestial wonders you can explore with a basic beginner’s telescope.

The Moon

The Moon is a perfect target for a small telescope. You’ll be able to see lunar craters, mountains, and other surface features in sharp detail.

The best views are around the time of a full moon when the sun fully illuminates the lunar surface. Track the phases of the moon to know when it will be at its brightest and most visible.


Gaze at the planets in our solar system, like Jupiter and its four largest moons, Saturn and its famous ring system, and Mars with its polar ice caps. Venus will appear as a crescent, and you may even spot a few of its cloud bands.

The details you can see will depend on the positions and distances of the planets, so check an astronomy app or skywatching guide to know when the planets will be at their most visible and close to Earth.

Deep sky objects

Some star clusters, nebulae, and galaxies are also within range of a 100mm scope.

Look for the Orion Nebula, a stellar nursery where new stars are born, the Andromeda Galaxy, our nearest galactic neighbor, and globular star clusters like Hercules Cluster (M13).

These and other deep sky objects will appear as fuzzy patches of light, but you’ll still be able to make out their distinctive shapes and see that they are made up of countless stars.

A small telescope may have limited light-gathering power, but for a beginner, it opens the door to exploring the cosmos in your backyard. With some patience and the right sky conditions, a 100mm scope can reveal celestial wonders you’ve never seen before.

So get out under the stars, point your telescope skyward, and unleash your sense of discovery. The universe is yours to explore!

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Planets of our solar system

With a 100mm telescope, you’ll be able to see amazing details of our solar system neighbors.

  • The moon will blow you away with craters, mountains, and vast seas of basaltic rock.

Even with a small scope, you can spot lunar landmarks like the Copernicus crater, the Lunar Alps, and the Lunar Maria. Start with lower power for a wide field of view, then use higher magnification to zoom in on areas of interest.

  • Mars reveals a rust-colored disk with surface features like Syrtis Major, a dark patch of volcanic rock, and the southern polar ice cap.

Around opposition, you may even spot white patches of clouds. With patience, you might glimpse the tiny pinprick of light that is Mars’ moon Phobos.

  • Jupiter’s cloud bands and Great Red Spot are visible, as are its four largest moons, Io, Europa, Ganymede, and Callisto. Watch as they orbit Jupiter and cast their shadows onto its clouds.
  • Saturn’s magnificent ring system is a jaw-dropping sight through a 100mm scope.

You can also spot several moons, including Titan, Rhea, and Dione. With a large telescope focal length, you can see a great deal of detail, including the many layers of clouds.

  • Uranus and Neptune appear as small blue-green disks, while Venus goes through phases like the moon.

However, remember that your viewing experience is influenced by factors like light pollution, viewing conditions, and telescope setup.

With a little practice, you’ll be exploring the solar system and discovering celestial wonders.

A smaller telescope can make deep sky objects reveal a universe of possibilities if you take the time to look.

So get out there and start observing! The night sky is calling.

Deep sky objects

With a 100mm telescope, you can glimpse into the depths of our universe and spot some spectacular deep-sky objects like galaxies.

Galaxies are massive collections of stars, gas, and dust bound together by gravity.

Even with a modest telescope, you’ll be able to see some of the brightest galaxies outside our own Milky Way.

Andromeda Galaxy (M31)

Our closest galactic neighbor, the Andromeda Galaxy, is also visible through a 100mm telescope. The Andromeda Galaxy is one of the most popular deep-sky objects for amateur astronomers.

At 2.5 million light-years away, it’s the farthest object visible to the naked eye brighter deep sky.

Through a 100mm telescope, you’ll spot its bright central bulge and dusty spiral arms. Andromeda is a spiral galaxy similar to our own Milky Way.

Through a larger telescope, you may be able to see the galaxy’s spiral arms and bright core.

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Nebula (M42)

While not technically a galaxy, the Nebula is a stellar nursery where new stars are born.

Located 1,300 light years away, it appears as a hazy patch of light in Orion’s sword.

A 100mm telescope will reveal delicate filaments of gas and dust within the nebula and a small open star cluster at its heart.

The M42 is an emission nebula, glowing from the radiation of hot young stars.

Whirlpool Galaxy (M51)

The Whirlpool Galaxy gets its name from its distinctive spiral arms.

At 23 million or more light years distant, it’s challenging to spot with a small scope but can be found with patience.

What you’ll see is a faint, fuzzy oval with hints of its spiral structure.

The Whirlpool Galaxy is interacting with its smaller companion galaxy, NGC 5195.

Their gravitational tug-of-war has shaped the Whirlpool’s winding arms.

Other galaxies to try for include the Pinwheel Galaxy (M33), a small irregular galaxy; and Bode’s Galaxy (M81), a spiral galaxy located in the constellation Ursa Major.

Glowing nebulae

With a 100mm telescope, you’ll be able to spot some of the most stunning celestial objects—glowing nebulae. Nebulae are massive clouds of dust and gas in space.

Although they may look like colorful clouds, they are the birthplaces of new stars and solar systems.

The Orion Nebula

One of the most famous nebulae is the Nebula, located in the constellation Orion. Through a 100mm telescope, you’ll be able to see the nebula as a fuzzy patch of light.

It has a blue-green tint from hot young stars embedded within.

The Nebula is a stellar nursery, where new stars are actively forming. Over 1,000 stars have formed in this nebula so far.

The Pleiades star cluster

The Pleiades, or Seven Sisters, is an open star cluster located in the constellation Taurus. Through a 100mm telescope, you’ll be able to see 6-8 stars in this cluster.

The Pleiades contains over 1,000 celestial objects, but only the brightest are visible without a large telescope. This cluster is dominated by hot blue stars that formed around 100 million years ago.

The Pleiades appears as a tiny “dipper” shape to the naked eye.

With some patience and the right conditions, you can observe glowing nebulae and distant galaxies through a modest 100mm telescope.

Start with the easiest targets like the Nebula and Andromeda Galaxy, then move on to smaller targets as your observing skills improve.

The wonders of the universe are within your reach.

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Star clusters

With a 100mm telescope, you’ll be able to spot some stunning star clusters in the night sky. Star clusters are groups of stars that formed together and are gravitationally bound, orbiting a common center of mass. They make for spectacular celestial sights.

Globular clusters

Globular clusters are dense spherical collections of hundreds of thousands of old stars. They orbit in a halo around galaxies. Through a 100mm telescope, you can see some of the brightest globular clusters, like M13 in Hercules and M22 in Sagittarius.

They will appear as fuzzy patches of light due to the sheer number of stars. Globular clusters are cosmic relics that provide clues about the early universe.

  • To find star clusters, use a star chart to determine their location based on the constellation they reside in.
  • Start with lower power (around 50x) to get the cluster in view, then increase to 100-150x for the best views.
  • Look for differences in color, brightness, and concentration of stars. Open clusters will have distinctive patterns, while globular clusters are densely packed.
  • Photograph your views through the eyepiece to capture these astronomical wonders. Even a smartphone can take decent pictures through a telescope, using long-exposure photography so it’s also an opportunity to get into astrophotography if you own a decent camera.

Exploring star clusters is a rewarding experience for amateur astronomers. With a 100mm telescope, you’ll get a glimpse into some of the most spectacular stellar formations in our galaxy and beyond.

Their beauty is a constant reminder of the universe’s infinite capacity for creation. Keep gazing up—celestial treasures are waiting to be discovered!

Double stars

With a smaller telescope like 100mm, you can start exploring some wonders beyond our solar system.

Double stars

Double stars, also known as binary star systems, are two stars that orbit around a common center of mass.

Through a 100mm telescope, you can see many bright stars like Albireo, a blue and gold pair, and Mizar, located in the handle of the Big Dipper, which features doubles that merely seem to be in close proximity.

Some other targets for a 100mm telescope include:

  • Open star clusters, like the Pleiades and Beehive clusters, contain hundreds of stars.
  • Bright nebulae, like the Orion Nebula, are stellar nurseries where new stars are forming.
  • Galaxies, including the Andromeda Galaxy.
  • The moon is where you can see craters, mountains, and other surface features.
  • The planets Jupiter and Saturn, where you may spot cloud bands, and Saturn, its ring system.

A 100mm telescope opens the door to observing a universe of wonders.

While more advanced instruments can reveal fainter and more distant astronomical objects, a small scope lets you start exploring the night sky at your pace.

Stargazing with a 100mm telescope is a fun and rewarding hobby for all ages.

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How much magnification do I need?

For most objects, start with lower power eyepieces (around 25mm to 40mm) to get wide field views in more detail.

The focal ratio of an optical system is the ratio of focal length to its aperture. The aperture is the diameter of the objective lens or a mirror – it defines how much light the telescope gathers and its maximum resolving power.

You can then increase magnification to around 150x to 200x for planets and the Moon. Higher powers often result in dim, blurry images, so start low and work your way up. The exact calculations are laid on knowing the telescope’s focal length, and magnification.

However, remember that higher magnification isn’t always better, as it narrows the field of view and requires more light to maintain image brightness.

Do I need any additional eyepieces or filters?

The eyepieces and filters that come with most 100mm telescopes will get you started, but you can enhance your experience with:

Additional eyepieces in focal ratio from 6mm to 40mm for a range of magnifications.
Color filters like red, blue, and yellow for enhancing views of planets and nebulae.
Neutral density filter and polarizing filter for cutting through light pollution and glare.
A glare-reducing moon filter for dimming the bright moon.

How do I find objects in the night sky?

To locate celestial objects, you’ll need:

1. A sky map or star chart showing the positions of stars, constellations, and objects for your location and time of year. Many are available as apps, software, or physical charts.
2. To get oriented, first, locate some major constellations like Orion or Ursa Major. Then star hop from bright star to bright star to locate your target.
3. For planets, note their position relative to the horizon, moon, and bright stars. They will move slowly over days and weeks.
4. Be patient and give your eyes time to adjust to the dark. The more you observe, the more you’ll get familiar with the night sky.

With some practice, you’ll be discovering galaxies, nebulae, and star clusters in no time.

So get out there, get a tabletop telescope, point your 100mm scope to the heavens, and enjoy exploring the universe!

Is 100mm good for a telescope?

With a 100 cm telescope, you can look at every planet except Pluto. It is capable of clearly capturing the moon’s rocks and craters in very precise detail.

You’re capable of seeing galaxies as well in only the aperture viewfinder.

What is 100mm in telescope view?

Since astronomers prefer metric methods, the aperture is generally measured in millimeters. In 100mm, that telescope’s focal length is equivalent to 3.9ins.

What is the max magnification for a 100mm telescope?

Optimal magnitude use is achieved when eyepieces are 0.7 mm-0.6 mm in diameter. Its no limit has a clear meaning but is rather an indication to maximize magnification.

A 100 mm telescope, therefore, has a maximum magnification of 142 times and a 200 mm telescope of 285-285 times. 

Orion SkyScanner 100mm TableTop Reflector is an ideal beginner’s telescope capable of many astronomical observations and providing hours of family fun exploring the cosmos.

Can you see Neptune with a 100mm telescope?

Neptune also does not appear faint. This light is bright enough for color vision with an Orion Skyscanner 100mm and a wide aperture.

Look for an almost identical hue to Uranus, but slightly brightener. There are a few additional variables that determine what you can view through your lens and the optical quality of the image.


So, there you have it, a whole universe of wonder and discovery awaits you with just a simple 100mm telescope. While it may seem like a small aperture, the sky holds endless secrets that are now unveiled to your curious eyes. Keep exploring, and you’ll continue to be amazed at how much there is to see.

New stars, nebulae, and galaxies will become familiar friends as your observing skills increase. Most of all, remember that you’re now part of a long tradition of amateur astronomers who have shaped our understanding of the cosmos. Get out there and start discovering!

Ida Stewart

I have had the incredible opportunity to work as a tour guide at the planetarium for over 5 years. Ever since I was a child, astronomy has held a special place in my heart, and I have nurtured a deep passion for exploring the wonders of the universe. Among all the celestial bodies, Mars has always fascinated me the most, captivating my imagination with its mysterious allure.

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