What Is A Compound Telescope? (Pros & Cons Explained)

what is a compound telescope

Having an interest in astronomy and telescopes is fun until the time comes when you have to make a decision of buying a telescope for yourself. And that is understandable, particularly if you are a beginner.

There are various types of telescopes available in the market. And choosing a suitable one based on the price and features can be very confusing. So, to help you out with your purchase decision, we are going to tell you everything you need to know about a specific type of telescope – Compound Telescope with its pros & cons explained!

Before that, let’s get acquainted with the 3 basic telescope types. Because that will help you understand why the article is solely about what a Compound Telescope is.

Refractor Telescope

refractor telescope pros cons

It is the most popular one for people who are not astronomers. It is very simply constructed and it has an easily usable lens to collect and focus light. It requires very low maintenance and is highly preferred by beginners.

Reflector Telescope

reflector telescope pros cons

A reflector telescope does not have a lens. Instead, it has a mirror to collect and focus light. The aperture of the refractor telescope and the reflector telescope is the same one. But reflector telescope comes with a cheaper price. Newtonian Reflector is the most popular reflector factor.

Compound Telescope

compound telescope pros cons

Compound Telescope is the most sophisticated telescope in the market and it shares the characteristics of both types of telescopes that have already been mentioned above. It contains mirrors to collect and focus light as well as lenses.

This kind of telescope has a more compact construction than the other two. That is why it can be used with less economical and less heavy mounts. Having the plus points of the other two telescopes, this one serves all the purposes very efficiently.

This telescope is also known as “Catadioptric Telescope” because the word catadioptric means “Due to both the refraction and the reflection of light”.

See? It has the good sides of both of the telescopes and it performs way better than them. Now the rest of the article will focus on the pros and cons of a Compound Telescope, its types and their characteristics. Do keep reading!

Pros & Cons Of A Compound Telescope

This part of the article will provide an explanation of the pros and cons of the telescope. Let’s go with the pros first.


  • Although it has a short tube, you can still use it for using a very long focal length. As a result, it can gain higher magnification so that you can easily and perfectly observe the moon and other planets with high magnification.
  • Again, the short tube of the telescope weighs a lot less even with large apertures than the other types of telescope that weigh a lot with the same apertures.
  • This telescope is very compact and user friendly. You can always carry it with you and can easily assemble or disassemble it while viewing the sky. This is a very important factor and you will realize it when you move it from your place to a distant site without struggling at all.
  • As mentioned already, this telescope has large apertures. One of the great advantages of telescopes with large apertures is that they have a higher angular resolution than the telescopes with short apertures. Besides, they ensure the ability to gather good light.

With these great advantages, there are some limitations as well. Let’s get to know about the cons now.


  • When it comes to observing deep sky objects such as planetary nebulas or galaxies, this telescope does not provide satisfactory performance. This is due to its focal ratio which is higher and its field of view which is narrower. However, you can still manage to find the nebulas if you use an eyepiece with a wider field of view in your compound telescope. You can also buy an eyepiece bigger in size to fix the focal length and reach the same magnification.
  • Due to the telescope’s complex design, while taking the telescope from one place to another, vibration can make the secondary mirror move a little. It can also happen for any change in the ambient temperature. But if you collimate your telescope regularly before or while planning to work with it, the problem can be solved easily.

Types Of Compound Telescopes

There are two types of Compound Telescopes in the market and they are widely used nowadays – Schmidt-Cassegrain and Maksutov-Cassegrain. The following discussion will discuss how they work and what their characteristics are.

Schmidt-Cassegrain Telescope

The main reason why the Schmidt-Cassegrain telescope has got huge popularity is its optical design which is very versatile and compact. You can easily recognize it for the length of its short tube. It has a primary mirror that contains a central hole.

There is another secondary mirror. The central hole reverses and focuses the light on it. When the light reflects, the reflection again passes the primary mirror’s hole and enters the focuser that lies in the telescope’s back.

The secondary mirror has a convex curvature. It lets the Schmidt-Cassegrain have a focal length that is almost 5 times longer than the length of the short tube.

On the contrary, the primary mirror has a 16-inch focal length. It implies that the focal length receives the light and it reflects in a length of 16 inches in the mirror. Then the secondary mirror is put in the middle of the focal point of the primary mirror and the mirror itself. The light is then reflected back to that primary mirror at a less sharp angle.

Usually, most of the secondary mirrors in this telescope provide a factor of maximum 5x magnification.


The corrector plate of this compound telescope is made of an aspheric lens. And so, the telescope has large apertures. This is because the body of the plate is very thin and it is easy to make.

It also gives the telescope an edge which enables the telescope to take less time to become thermally equalized in accordance with the temperature of the venue where you choose to view the sky.

Then comes the secondary mirror that lets the telescope get rid of the diffraction spikes. With its collimation, there is another advantage. Its collimation is solid and so it rarely requires regular collimation during the viewing period.

Maksutov-Cassegrain Telescope

A lot of similarities are noticed in the way Maksutov-Cassegrain and Schmidt-Cassegrain telescopes work. Because they both have a spherical primary mirror coupled with a secondary mirror.

There is only one dissimilarity in the telescopes’ ways of working which is that this Maksutov-Cassegrain telescope does not have a Schmidt plate in it. Instead, it has a lens shaped like a meniscus at its front aperture.

This compound telescope’s secondary mirror has a metal coating in the back of its meniscus lens. It enables the Maksutov-Cassegrain to have a tiny number of chromatic aberration. And producing the spherical aberrations is the job of the primary mirror.


The Maksutov-Cassegrain telescope has a corrector plate named the Maksutove corrector plate. This plate bears a spherical lens which is highly curved. It makes an improvement in the number of both spherical and chromatic aberrations.

The plate is thicker than that of the Schmidt-Cassegrain telescope. Due to its thickness, the apertures in this kind of compound telescope are usually small in size.

Another important factor is that the secondary mirror in this telescope is smaller than that in the Schmidt-Casserine telescope. This is less obstructive for the light path and it causes the view or image to be brighter and sharper.

My Recommendation For Beginners

Even after you figure out which telescope you want to buy, the confusion of selecting a telescope from a series of brands still remains. And the budget matters too.

So, here we are recommending you a telescope for each type, one Schmidt-Cassegrain Telescope and one Maksutov-Cassegrain Telescope.

The first one is from Celestron. It’s the NexStar 6SE Computerized Telescope. Though the price can exceed the $1000 range, it is certainly one of the best Schmidt-Cassegrain telescopes money can buy. Currently, it has won the ‘Best-Seller’ rank on Amazon. This telescope will come in handy for advanced users as well.

Here are some of the features you’ll get:

  • Despite having a compact form factor, the light gathering capability of this telescope is perfect for observing our solar system
  • Comes with a fully computerized Go-To mount. This is perfect for beginners as the mount will automatically track and locate the celestial objects for you. You don’t have to do this on your own! Moreover, the mount is equipped with the information of 40,000 celestial objects. So, you can automatically track and locate pretty much everything within our solar system.
  • Free software included for an interactive sky simulation.
  • Comes with 2 year warranty and 24×7 support from Celestron’s US team.

But if you are running low on budget, then you can go for the NexStar 127SLT Computerized Telescope. It is a Maksutov telescope that you can get at around $500 price range! It is compact and portable. With its sophisticated specs, it should serve your purpose just fine.

  • Like the previous recommendation, this telescope is also equipped with the information of 40,000 celestial objects. The computerized mount will automatically track the star, galaxy, or nebulae for you.
  • Has the capability to locate celestial objects beyond our Solar System.
  • Comes with 2 year warranty and 24×7 support from Celestron’s US team.

Final Words

That is all the basic and important things that you should know about a Compound Telescope before you decide to buy one. With the pros and cons explained, now you also know why you should prefer this type of telescope to the other two, don’t you?

We have also talked about the types of compound telescopes, given you our recommendations with prices so that you can select one that suits both your purpose and budget. We are optimistic that you have found them helpful and soon, with the right telescope, you will start enjoying your stargazing nights full on!


I have wondered how the Stars and Moons look like for many years. I’ve fallen in love with Cosmology since I was a boy. I am writing these articles to share my love for astronomy with you.

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