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Telescope Buying Guide - What Can I See Through My Telescope?

Posted by Ben Touchette on

What Can I See Through My Telescope - Stellar Telescope

Here Is What You Need To Know About Buying Your First Telescope

Here we go! One of the first questions most people will ask when starting their search for the perfect telescope is what can you actually see through the telescope? And that is a great question.

There are many ways to answer this, but also many pieces to consider before making the final and exciting choice of purchasing a telescope. Don't let that scare you away though! We will break it down for you step-by-step in this article. Here are some key factors to first consider:


As any well-informed astronomer, amatuer or otherwise, can tell you, aperture length (diameter of a telescope’s primary lens/mirror) plays a large part in any choice involving what you can see through a telescope. In this article, you will receive some advice on the aperture size, along with the differences in main types of telescopes’ aperture size.


Location can also have a very strong impact on how well (if any at times) you can see the starry night sky. When considering the size of apertures on a telescope, one basic rule of thumb to keep in mind is if the aperture is approximately 6” or higher, you really will need a dark site to have an effective and enjoyable time viewing the cosmos. (A dark site is a large area, preferably as big as you can manage, but a meadow or field usually offers the most common sites, that is away from street lights and building lights.)

✅ Pro Tip: Even though telescopes with large apertures pick up a lot of the dim objects in the sky, they also pick up a whole lot of light pollution if you are near building lights or street lights!


So...What Are The Types Of Telescopes?

There are three primary types of telescopes: Refractor, Reflector, and Catadioptric. In each of these following sections, you’ll find a brief explanation of what might be considered benefits and drawbacks of each type of telescope. Let's start with the reflector...

Reflector Telescopes: The Best Beginning Telescope


  • Considered the best “bang for your buck” type
  • Usually more bright images than refractor, almost always more than catadioptric
  • Relatively low price (even for large ones)
  • Much larger aperture sizes for the same price of half aperture size of either other type


  • Diffraction: Also considered scattered light, reduces the contrast of objects on the moon or other planets, making it more difficult to make out finer details.
  • Coma: Optical defect that causes stars to appear triangular the further out of center the object is being viewed. Tends to be less of an issue because objects that you want to observe are usually observed in the center of the view plane, instead of the edges where the coma is more apparent.
  • Size and weight
  • Added maintenance needed (requiring either money or lots of time)

Refractor Telescopes: The High-Quality and High-Clarity Telescope


  • Longer lasting
  • Smaller aperture sizes are as strong as larger aperture sizes of the others
  • Highest light transmission: The percentage of light collected by the telescope that actually reaches the eye, typically around 90% of total light collected.


  • The most expensive type usually (especially larger sizes)
  • Light weight in smaller sizes, but become more bulky more quickly
  • Chromatic aberration: A optical defect that creates a faint pale purple/violet halo or hue around some brighter stars, planets, and sometimes the moon.

Catadioptric Telescopes: The All-Purpose Telescope


  • Combines many good features of both refractor and reflector
  • Reduced coma when compared to reflectors
  • No chromatic aberration when compared to refractors
  • Usually uses fork mounts, which have less vibrations and more secure
  • More portable than similar sized refractors or reflectors


  • Cost, especially when compared to reflectors, but comparable to refractors
  • Not as wide of a contrast range on planets and moons, because of the extra secondary mirrors scattering more light away from the eye
  • Tend to have dimmer images

With each type of telescope, whether it be the user and beginner friendly reflector, the robust but expensive refractor, or the all around benefits of a catadioptric, not all types of telescopes would work for each individual that might consider buying one. The reflector might be one of the most recommended types for beginning astronomy hobbyists, but if you live in an apartment in a city, you may want to consider a small refractor because of the hassle in taking a telescope up an elevator.

What Can You See Through A Telescope Based On Its Aperture?

Now that you've learned about the different types of telescopes, let's talk about what you can see! Aperture is probably the most important factor when deciding on your new telescope. Here is some great information about what you can see, what you can expect to pay and the maintenance required with it.

Small Aperture: 60mm - 90mm Refractor, 70mm - 120mm Reflector and Catadioptric

✔ Main things you can clearly see through this telescope aperture size:

  • binary stars with angular separation of over 1", faint stars (up to 13 stellar magnitude)
  • polar ice caps and maria on Mars during oppositions
  • structure of sunspots, granulation and solar flares (with an aperture filter)
  • Phases of Mercury and Venus
  • all the Messier objects
  • some details are resolved on the brightest and largest objects
  • details are not resolved during observations of most galaxies
  • Cassini Division in the rings of Saturn and 4-5 moons
  • Mostly view of atmospheric bands on Jupiter and the GRS, shadows cast by moons onto the planetary disk

✔ Average prices:

  • Refractors: Range from $100 - $800
  • Reflectors: Range from $120 - $1000
  • Catadioptric: Range from $500 - $4,300

✔ Maintenance level:

  • Refractors: Best for beginners
  • Reflectors: Best for beginners
  • Catadioptric: Relatively comfortable for beginners


Medium Aperture: 90mm - 130mm Refractor, 120mm - 150mm Reflector and Catadioptric

✔ Main things you can clearly see through this telescope aperture size:

  • Details of lunar highlands and craters (3-4 km in diameter)
  • Spots in the atmosphere of Venus may be seen with a blue filter
  • plethora of faint asteroids and comets
  • spiral features of the brightest galaxies (M33, M51)
  • hundreds of clusters, nebulae and galaxies
  • atmospheric bands on Saturn
  • Numerous details on the surface of Mars during oppositions

✔ Average Prices

  • Refractors: Range from $700 - $10,000
  • Reflectors: Range from $400 - $14,000
  • Catadioptric: Range from $1,000 - $4,000

✔ Maintenance level:

  • Refractors: Can be used for any levels
  • Reflectors: Can be used for any levels
  • Catadioptric: Relatively comfortable for beginners


Large Aperture: 130mm+ Refractor, 150mm+ Reflector and Catadioptric

✔ Main things you can clearly see through this telescope aperture size:

  • Thousands of galaxies, star clusters and nebulae
  • Binary stars with angular separation of 0.5" (under ideal conditions), faint stars (up to 15 stellar magnitude)
  • Most features of a number of galaxies and nebulae may be observed (with minimal light pollution)
  • Some globular clusters are resolved into individual stars
  • Lunar features (2 km in diameter)
  • 6-7 moons of Saturn, planetary disk of Titan may be observed
  • Clouds and dust storms on Mars
  • Pluto as a faint star
  • Triton, Neptune's moon

✔ Average prices:

  • Refractors: Range from $5,000 - $27,000 and up
  • Reflectors: Range from $1,200 - $36,000 and up
  • Catadioptric: Range from $1,700 - $20,000 and up

✔ Maintenance level:

  • Refractors: Best for experienced users
  • Reflectors: Best for experienced users
  • Catadioptric: Relatively comfortable for beginners

What it comes down to is this: Aperture, type of telescope, and sometimes location, to find out most of what you can see through it. If the price is a major constraint, it is recommended for beginners to start on reflectors, as they may be higher maintenance as they get bigger, but generally are significantly cheaper than comparable refractors and catadioptrics. If maintenance is your main concern, choose the refractor with the largest aperture you feel comfortable affording. For ease of alignment and portability, choose catadioptric as it is the least bulky and easiest to fine tune with it’s mount out of the types.

The biggest piece of advice to offer is once the type of telescope is chosen, go with the biggest aperture that your budget allows. But, if you are new to this hobby, start with a simple and small reflector, so that you can test the waters in astronomy, and reach for the skies later on when you are ready for the larger telescopes!

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