I know you would be excited to buy your first telescope. Well, I was. Or maybe you already did and are not happy with it or just want to add another arrow to your quiver. In this post, I will try to help you make a decision. Whether or not it is the right choice is subjective but I hope it’s an informed one, after all, a good telescope can leave an “astronomical” hole in your pocket!

I hope, from the previous posts on each of the three major kinds of telescopes, you now have at least a brief idea of the different major design differences! Don’t worry if you forgot the details (I don’t even expect you to remember each sub-type and the design intricacies)! The details were for those of you who really wanted to dive into the depths and also to, at least, make you aware of the existence of the different types.

Let’s first list down the pros and cons of each of the three major types.

Refracting Telescopes

Pros:

• Few optical constituents
• Easy to use
• Require less maintenance
• Brighter and sharper image per inch of aperture, compared to their counterparts
• Excellent for lunar and planetary viewing

Cons:

• Larger and bulkier per inch of aperture, compared to their counterparts
• Not great for faint deep sky objects (DSOs) because of generally small apertures (light gathering ability)
• More expensive than counterparts of an equal size aperture
• Generally available in small apertures
• Not very portable for large apertures. Smaller apertures would mean limited viewing capability
• Suffer from chromatic and spherical aberrations
• Large apertures suffer from lens sagging

Reflecting Telescopes

Pros:

• Compacter per inch of aperture, compared to refractors
• Less expensive per inch of aperture, compared to refractors, owing to mirrors being cheaper than lenses
• Easy to use
• Less chromatic and spherical aberrations
• Excellent for both planetary and deep sky objects (DSOs)
• Available in larger apertures, compared to refractors
• Owing to the use of mirror as the objective, compared to refractors that use a lens, sagging is not a major issue for large apertures.
• Generally have smaller focal lengths than the catadioptric telescopes, which means wider field of view

Cons:

• More number of optical constituents than refractors, which means frequent calibration required
• Generally an open configuration, which means optical elements are more susceptible to environment artifacts
• Require more maintenance than refractors
• Images not as bright and sharp as with refractors of similar aperture
• Less portable than similar size aperture catadioptric telescopes
• Not very portable for large apertures. Smaller apertures would mean limited viewing capability
• Suffer from distortions, due to the use of a secondary, compared to single-piece objective used in refractors

Catadioptric Telescopes

Pros:

• Much compacter per inch of aperture, compared to their counterparts
• Closed configuration, as opposed to reflectors, which means less maintenance
• Less chromatic and spherical aberrations than refractors
• Excellent for both planetary and deep sky objects (DSOs)
• Great for astrophotography
• Available in larger apertures, compared to refractors
• Much more portable than refractors and reflectors for an equal size aperture

Cons:

• More number of optical constituents than their counterparts, which means frequent calibration required
• Require frequent calibration, as opposed to refractors
• More expensive than similar size aperture reflectors
• Suffer from distortions, due to the use of a secondary, compared to single-piece objective used in refractors
• Usually have longer focal lengths of the objective than their counterparts of equal size aperture, which means smaller field of view (but this can be very easily corrected with the use of long focal length eyepieces or cheap focal reducers, which we will see in the posts The Paraphernalia of telescopes (The Indispensables and The Luxuries).

Which factors matter the most to you will be subjective. If money is not a factor to you but portability is, then I recommend you go with a catadioptric telescope. If you think you can manage lugging a slightly bulkier telescope around and want to cut down on your budget, you can go with a reflector. If your target is mainly planetary viewing with brilliantly bright and sharp images, want very large apertures but do not want to do frequent calibrations and maintenance, but have the means to carry around a very bulky telescope, then you can go for a refractor. Again, this is all subjective and the context is stargazing. For astrophotography, although you would still need a camera (usually a DSLR) and other accessories, the refractors and reflectors are generally not a great choice for that.

Although we will study the accessories in a different post, I would like to briefly mention the fact that all astronomical telescopes are used with mounts. Mounts are basically the holders of the telescopes, e.g. commonly used tripods for cameras.

The mounts (usually, for ease of reference, the telescopes themselves) are generally categorized into two main categories: Manual and GoTo. When someone says a telescope is GoTo, it is, in fact, the mount that is so and not the telescope itself.

Manual telescopes, as the name suggests, need to be maneuvered manually in order to point to different objects in the sky. However, these manual telescopes can be fitted with motor and drives to add ease of maneuverability.

GoTo telescopes, on the other hand, are already computerized and motorized. They generally come with a pre-packaged handset that is used to control their motion. As they are computerized and usually are linked to a database of celestial objects, they can automatically point to the desired object with the press of a few buttons on the controller. These are very popular with beginners.

That being said, no matter how convenient the GoTo telescopes might be, it is generally advised that beginners should learn the sky and for that, start with non-computerized telescopes. But again, the choice is yours.

There is also another line of categorization for the mounts, based on the type of motion and alignment, viz. Fixed, Transit, Altazimuth (AZ), Equatorial (EQ) and a few more. We will study that in the post The paraphernalia of telescopes – The Indispensables.

An important thing that you should keep in mind while buying a telescope is that you should avoid buying one which is advertized with extremely-high-magnification and/or is cheap (usually less that USD 200, commonly sold in department stores).

As noted in the respective posts on the three kinds of telescopes, the Apochromatic design of refractors, the Newtonian design of reflectors and the Cassegrain design (Schmidt-Cassegrain and Maksutov-Cassegrain) of catadioptric telescopes are the most widely used and popular designs in each of the three categories.

There are a myriad good manufacturers of astronomical telescopes. Meade generally manufactures research-grade refracting telescopes and are usually quite expensive. Some of the popular manufacturers of telescopes for beginners and intermediate astronomers are Orion, Sky-Watcher, Celestron. Orion and Sky-Watcher mostly produce reflectors, and Celestron is mostly famous for Catadioptric telescopes.  All these brands manufacture great telescopes, although they might be sold in different countries under different banners).

Mind you, there are many factors that contribute to the price of a telescope. Aperture is one of them and happens to be the most prominent one. An 8inch aperture telescope can easily cost a few couple of hundred of dollars more than a 6inch one (of the same type). So, be careful, before you make a choice!

Here are a few examples in each of the three main categories. Please note that I do not endorse any of these products. They are just examples.

Refracting:

Meade 102mm AZ Refractor – Note that 102mm is the aperture, and AZ is the mount type – Altazimuth.

Meade 130mm f/7 Triplet APO Refractor – 130mm aperture, f/7 focal ratio, Triplet APO refractor type – Triplet Apochromatic.

Orion 90 mm EQ Achromatic Refractor -90mm aperture, EQ mount type – Equatorial, Achromatic refractor type

Reflecting:

Sky-Watcher 8″ Dobsonian – 8inch aperture, Dobsonian is a special type of Newtonian reflector which we will discuss in another post, The Paraphernalia of telescopes – The Indispensables.

Orion 6″ EQ Newtonian – 6inch aperture, EQ mount, Newtonian reflector.

Catadioptric:

Celestron 8″ GoTo SCT – 8inch aperture, GoTo (computerized mount), Schmidt-Cassegrain catadioptric

Celestron 127mm GoTo Mak – 127mm aperture, GoTo (computerized mount), Maksutov-Cassegrain catadioptric

---

But wait! Before you fire up your car engine or hit the checkout button online, make sure you peruse the next posts, The Paraphernalia of telescopes (The Indispensables and The Luxuries). There we will see the different accessories that are used with telescopes, including mounts, eyepieces, filters among others. While some accessories are must-haves, some provide enhancements, some can even be used to fix the shortcomings in the telescope of your choice with just a few more dollars instead of having you go for a much costlier telescope (in the latter case, good luck sky gazing all day until you next paycheck!). It is also wise doing some more research online or talk to experts on astronomy forums or even talking to your local dealer of telescopes (though, you need to be smart there to know if they are being biased!).

Good luck, my friends! Happy stargazing!