What Are The Different Types Of Telescopes?

Stargazing with the naked eye has its charms but you can see so much more with a telescope. If you are ready to do some backyard astronomy, then begin your journey by acquiring the right equipment for your needs. Before you purchase anything, you should become familiar with what are the different types of telescopes. There are plenty if you want an exhaustive list but hobbyists can focus on the three most popular ones. These are the refractor telescope, the reflector telescope, and the catadioptic telescope.

Read on to learn more about how they work, what benefits they bring, and what downsides you should look out for.

The Refractor Telescope – Dioptric

refractor telescope

How Does It Work?

Refractors use lenses to gather light. These have been around since the time of Galileo in the 17th century. The design may be simple but it works. Galileo was able to observe the heavenly bodies so well that his theories changed the way that we view our place in the solar system. Hundreds of years later, several improvements have been introduced and refractors are better than ever. They work by bending light, also known as refraction. At the front end is a large glass plate called the objective lens. The light is focused and the image is magnified at the eyepiece.

What are the Benefits?

The straightforward design of refractor telescopes make them the perfect companion for absolute beginners. You just point the scope where you wish to look and peek through the eyepiece. It usually works well every time with no collimation or alignment adjustment necessary. The aperture is maximized for light gathering. There are no obstructions to the image. It can cool down fast so thermal effects are reduced. This kind of telescope can be used for both the sky at night and the surrounding landscape during the day. You have a slim tube that is lightweight and highly portable for observing at different locations.

What are the Downsides?

This type of telescope tends to have a relatively small aperture compared to others. This limits the amount of light that it can gather. You can find ones with larger apertures but these models tend to be quite expensive. Be prepared to shell out a lot for the conveniences that this brings. You might also notice some chromatic aberration in the image. When light hits the objective lens, it splits into various wavelengths and meets back at the focal point. However, some wavelengths may be a bit off such that colors will be a bit off and sharpness can suffer.

The Reflector Telescope – Newtonian

reflector telescope

How Does It Work?

Reflecting telescopes use mirrors to bounce light. This was a later invention that was conceived as an alternative to the refractor design. The credit goes to another famous figure, Sir Isaac Newton, who came up with it also in the 17th century. There are several variations of the reflecting telescopes today. His work is characterized by the presence of a spherical primary mirror. You might see this kind of telescope being called a Newtonian reflector. Light is gathered in a wider tube with a mirror at the end, then bounced to a secondary mirror at the top, and onto the side where the eyepiece is located.

What are the Benefits?

Reflectors are able to gather more light compared to refractors thanks to their large apertures. This enables astronomers to see the image brighter and sharper than in refractors. They do not suffer from chromatic aberration so the colors you will see are quite faithful to what is real. They are just as easy to use since there are only a few parts. They are also inexpensive to build so they are quite affordable to entry-level users such as students. If you want excellent value for money, then this is a great choice to make.

What are the Downsides?

Take note of the downsides to this design as well before making a purchase. A refractor telescope is sealed while a reflector is open at the top. The optics are exposed to dirt so be careful when using and storing them. Always put the cap on when idle to prevent dirt build-up. The optical components can get out of alignment from time to time so you need to check and set things right. This is a process called collimation. It can be daunting at first but it gets easy once you master it. You need to wait for it to cool down for a longer period. The presence of the secondary mirror at the top creates an obstruction for the light.

The Catadioptic Telescope – Schmidt-Cassegrain

catadioptric telescope

How Does It Work?

So we’ve learned that the refractors use lenses while the reflectors use mirrors. This third type incorporates both. Designs vary a bit with the most popular being the Schmidt-Cassegrain (SCT) and the Maksutov-Cassegrain (MAK). The SCT features a perforated spherical primary mirror and a convex secondary mirror. Behind this is a thin corrector lens. Just like in reflectors, the primary mirror is at the back. Just like the refractors, the eyepiece is also at the rear while the secondary lens is at the top. As for the MAK, you will also see a perforated primary mirror but this has a thicker corrector lens within which there is a secondary mirror.

What are the Benefits?

Whereas reflectors and refractors suffer from different types of optical aberrations, catadioptic telescopes are able to correct them so you can get the best images possible. It’s a great option if you want to observe the planets in detail. Viewing is comfortable through the eyepiece. You don’t have to worry about dirt since the tube is closed. The tube is also small and lightweight, making it portable enough to take on hiking trips for viewing at the peaks. These telescopes give you the best of both worlds while eliminating much of the drawbacks of the two previous designs.

What are the Downsides?

However, you should be prepared to shell out quite a bit of money for the privilege of owning one. They also require special mounts. The field of view is smaller and the secondary mirror creates an obstruction just like in reflectors.

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