Understanding the Different Types of Telescopes

Telescopes have long been the gateway to exploring the wonders of the night sky. Whether you’re a seasoned astronomer or a beginner with a passion for stargazing, understanding the different types of telescopes available is crucial in finding the perfect instrument that suits your needs. In this comprehensive guide, we will delve into the world of telescopes, exploring the primary types and their unique features. From refractors and reflectors to catadioptric telescopes, we’ll uncover the strengths and limitations of each design, helping you make an informed decision.

1. Refractor Telescopes: The Best and Worst for Beginners

One of the oldest and most recognizable types of telescopes is the refractor telescope. Utilizing specially designed lenses to focus incoming light, refractors offer crisp and clear images of celestial objects. These telescopes have a long and illustrious history being designed in Middelburg Netherlands in 1608 by an ingenious eyeglass maker named Hans Lipperhey, who put two glass lenses together in a tube, effectively creating the first ‘refracting’ telescope.

An excellent beginner refractor telescope
Celestron AstroMaster 90EQ Refractor Telescope

1.1 The Inner Workings of Refractor Telescopes

The optical system of a refractor telescope consists of a front lens or lenses, known as the objective, and an eyepiece at the rear. The objective lens is responsible for gathering and angling incoming light, bringing it to a focal point at the eyepiece where it can be magnified for observation.

1.2 Advantages and Limitations of Refractor Telescopes

Refractor telescopes offer several advantages that make them popular among astronomers. Their sealed tube design makes them virtually maintenance-free, with no need for periodic collimation like reflector telescopes. Additionally, refractors are well-suited for observing celestial objects during both daytime and nighttime, making them versatile instruments.

However, refractor telescopes also have some limitations. One common issue is chromatic aberration, which occurs when different colors of light are refracted at slightly different angles, resulting in color fringing around objects. This phenomenon is more pronounced in lower-cost refractors with doublet lenses. Higher-end doublets and triplets, on the other hand, are designed to minimize chromatic aberration, offering superior image quality.

Since there is less scattering of light, refractors tend to have higher contrast than reflectors providing excellent views for their size.

The last and one of their biggest advantages is they are faster and easier to set up, requiring less cool-down time before they can be used, which makes them excellent choices for a “grab-and-go” telescope.

1.3 Disadvantages and Cautions

Since the construction of refractors is so simple, there is a huge number of cheap refractors flooding the market. Some are pretty much a semi-clear piece of plastic glued inside a hollow plastic tube with another semi-clear piece of plastic acting as an eyepiece.

There is a massive difference between an inexpensive but good refractor telescope like Celestron AstroMaster 70AZ Refractor Telescope and a Gskyer 70mm AZ Mount Astronomical Refracting Telescope even though there is little difference in price. The former would make a nice beginner telescope for your children, the latter will do little more than make everyone upset (your kids because they can’t see diddly, you for being the chump who bought them useless junk).

It is so bad that people have had to make entire websites dedicated to helping people who bought the cheaper scopes figure out how to use them and show them what can and can not be done with them like gskyertelescopes.net. The manufacturers are simply giving them a single sheet of paper with very rough assembly instructions and telling them “good luck!”

An excellent beginner Newtonian telescope
Celestron AstroMaster 114EQ Newtonian Telescope

2. Reflectors: Harnessing the Power of Mirrors

Reflecting telescopes, also known as reflectors, utilize mirrors to gather and focus light. This design offers several advantages over refractors, making them a popular choice among astronomers of all levels. These require more setup, longer cooling times, and constant maintenance but provide brighter views allowing you to see fainter objects.

2.1 The Magic of Reflecting Telescopes

At the heart of every reflecting telescope is a primary mirror that captures and reflects incoming light. This mirror is typically concave in shape, directing the light towards a secondary mirror positioned near the front of the telescope tube. The secondary mirror then reflects the light out of the side of the telescope, allowing for easy observation through an eyepiece.

These are typically Newtonian telescopes and can be either mounted on a tripod or for larger models, set inside a Dobsonian base. Interestingly enough, the design of the telescope is identical even though one is called a Newtonian after the designer of the telescope, and the other a Dobsonian after the designer of the base.

2.2 The Benefits and Considerations of Reflectors

Reflecting telescopes have numerous advantages, including cost-effectiveness and a wide range of available apertures. Due to the simpler design and the use of mirrors instead of lenses, reflectors tend to be more affordable than refractors of the same size. This makes them an attractive choice for beginners or those on a limited budget.

Another advantage of reflectors is their ability to produce bright and detailed images. Since you are likely to have a larger aperture on your reflector, the primary mirror gathers a significant amount of light, allowing for better visibility of faint objects in the night sky. Additionally, reflectors are not susceptible to chromatic aberration, which can be a limiting factor in refractor telescopes.

However, reflector telescopes also have their issues. One drawback is their open-tube design, which makes them more prone to dust and debris accumulation. Regular cleaning and maintenance are necessary to ensure optimal performance. Additionally, reflectors often produce an inverted or flipped image, which can be disorienting for beginners. However, this can be easily remedied by using additional accessories like finderscopes or red dot finders.

Reflectors require more cool-down time, particularly with larger models. They often have fans at the bottom of larger models to help cool the primary mirror faster. Viewing before the mirrors have acclimated to the surrounding air temperature can present the viewer with poor views.

Lastly, reflectors need to be collimated frequently to provide good images. While this is a fairly fast and painless operation once you learn how and get some practice, particularly if you purchase a laser collimator, it is still an extra layer of work necessary to make use of this type of telescope.

3. Catadioptric Telescopes: The Best of Both Worlds

Catadioptric telescopes, also known as compound telescopes, combine the benefits of lenses and mirrors into a compact and versatile design. These telescopes offer a unique optical system that provides excellent image quality and portability. This comes at the expense of extended cool-down times, increased costs, and a heavy telescope.

A higher-end telescope but still excellent for beginners
A Celestron 8″ SCT on a GOTO mount

There are two popular types of catadioptric telescopes, Schmidt-Cassegrain (SCT) and Maksutov-Cassegrain (MCT). While there are other types, these are the ones you will most likely run into, with the Schmidt-Cassegrain being the most popular of the two.

3.1 Understanding the Inner Workings of Catadioptric Telescopes

The optical system of a catadioptric telescope consists of both lenses and mirrors. The light enters the telescope through a corrector plate, which acts as the front lens. The light then passes through the corrector plate and is reflected by a primary mirror at the back of the telescope. Finally, a secondary mirror reflects the light back through a central hole in the primary mirror, allowing for observation through an eyepiece.

3.2 The Advantages and Considerations of Catadioptric Telescopes

Catadioptric telescopes offer a range of advantages that make them an appealing choice for both beginners and experienced astronomers. Their compact and portable design makes them easy to transport and set up, allowing for stargazing adventures on the go. Additionally, catadioptric telescopes are known for their versatility, offering various focal lengths and apertures to suit different observing needs.

One consideration when using catadioptric telescopes is the need for occasional collimation. While not as frequent as pure reflectors, periodic adjustments may be necessary to ensure optimal performance. However, modern catadioptric telescopes often come with built-in collimation mechanisms, simplifying the process for users.

3.3 Schmidt-Cassegrain or Maksutov-Cassegrain?

SCTs and MCTs are very similar, both using lenses and mirrors to provide the best of both worlds. There is a lot of technical information as to which is better at what and why, but that is beyond the scope of this article (pun intended!) so I will just give you the basics.

MCTs usually have better image quality and higher magnification than a comparable SCT, they are also slightly more expensive, weigh more, and provide a dimmer image (this is normal since it provides more magnification). If I was looking to view nebulae, open clusters, and constellations I would take an SCT. For globular clusters, splitting stars, planetary, and high-magnification views of the moon, an MCT would be my choice.

4. Choosing the Right Telescope for Your Needs

Now that we’ve explored the primary types of telescopes, it’s time to consider which one is the best fit for your needs. When choosing a telescope, several factors should be taken into account, including your observing goals, budget, and level of experience.

4.1 Factors to Consider When Choosing a Telescope

4.1.1 What will you actually use?

This may sound silly, but I have seen it more times than I can count. People buy a telescope that is too cheap to actually see anything any better than they could with their unaided eyes, or they buy one that is so huge and/or complex that they just don’t want to go through the hassle of dragging it out and setting it up.

Therefore the primary consideration, above and beyond anything else, is to think about if you honestly will use this telescope when the opportunity arises. A $130 little refractor is better than an $11,000 20″ Obsession Dobsonian if you will use the refractor and the Dobsonian never gets wheeled out of the garage.

Don’t be tricked into the “better views” argument often made for bigger and/or more expensive telescopes. The best views are had by the person out using their telescope.

4.1.2 Observing Goals and Realistic Expectations

Before purchasing a telescope, it’s essential to determine your observing goals. Are you primarily interested in visual observation or do you plan to delve into astrophotography? Are you more into widefield (large expanses of the sky), viewing the moon, or are you looking for something to get serious detail out of Saturn? Different types of telescopes excel in different areas, so it’s crucial to align your goals with the telescope’s capabilities.

You should also look into what telescopes in your price range can actually deliver. You can see the rings of Saturn and some of Jupiter’s moons with virtually any reasonable beginner telescope, but no telescope for any amount of money is going to show you Neptune as anything more than a dot in the sky. And I mean any amount of money, even if your last name is Bezos.

There is little as frustrating as spending your hard-earned money on something only to find out later that it could not do what you wanted.

This works the other way too, spending too little because you “only” want to do something simple, you don’t need a powerful telescope, you aren’t trying to be a professional astronomer. That super-cheap department store telescope is not worth the little you paid for it, heck, it wasn’t worth the gas you burned driving to pick it up. Got it delivered for free? It wasn’t worth the calories you burned clicking the Buy Now button either.

4.1.3 Budget

Budget plays a significant role in telescope selection. Refractor telescopes tend to be more expensive per inch of aperture, especially as you move into larger apertures. Reflecting telescopes offer a cost-effective option, particularly for those looking to maximize aperture size but require more maintenance and longer cool-downs. Catadioptric telescopes require even more time to cool down, are somewhat more complex to set up and use, but are smaller than many reflectors and cheaper per inch than refractors.

Used is a good option, but only when purchased from somewhere or someone that can give you assistance and/or a refund if the item does not work. I highly recommend staying away from pawn shops, yard sales, and online resellers (eBay, Facebook marketplace, etc) for your first telescope as you do not have enough knowledge and experience to know how to keep from getting taken by a defective item.

If you are intent on buying used, find your local astronomy club and show up to a meeting. Ask around and you are sure to find people who are upgrading their scopes, or know of someone who is. These are people who know what to look for and can help you get an excellent telescope that fits your needs at a reasonable price. If you are in the United States, you can check out go-astronomy.com to find the club closest to you.

No idea where to start or what a reasonable telescope should cost? No problem! Check out this article on the best beginner telescopes.

4.1.4 Level of Experience

Consider your level of experience when choosing a telescope. If you’re a beginner, user-friendly options like Dobsonian telescopes or refractors may be a good starting point. For more experienced astronomers, advanced designs like Schmidt-Cassegrains or apochromatic refractors offer greater versatility and performance.

Also, consider the mount when thinking of a purchase as an equatorial mount will be more complex to set up and use than an altitude azimuth model. The flip side of that is that an EQ mount is far superior for advanced users and required for long-exposure astrophotography.

4.2 Making an Informed Decision

By evaluating your observing goals, budget, and level of experience, you can make an informed decision when selecting a telescope. Remember that the best telescope is the one that you are comfortable using, that you actually will drag out and use, and one that suits your specific needs. Don’t forget to pay attention to the mount, as it can significantly enhance your stargazing experience.

5. Conclusion

The world of telescopes is vast and fascinating, with each type offering its own unique advantages and considerations. Whether you choose a refractor, reflector, or catadioptric telescope, each instrument has the power to unveil the mysteries of the night sky. By understanding the inner workings and strengths of each design, you can be sure to get the tool that best suits your interests and budget. So, take the time to explore the different types of telescopes, weigh the options, and prepare for unforgettable celestial adventures. Clear skies await!