Not sure what telescope to buy? Confused about refractors vs reflectors telescopes. I know when I first became interested in stargazing, I thought telescopes were just telescopes. There are a lot of differences, however. This article covers the ins and outs of refractor vs reflector telescopes, differentiating two of the most common telescope types for backyard astronomy.
What is the main difference between a refracting telescope and a reflecting telescope? The main difference between a refracting and a reflecting telescope is that a refracting telescope uses lenses to gather and focus light and a reflecting telescope uses mirrors. While reflectors can have large mirrors for better light collection, refractors have good contrast and sharpness, are light and transportable, and need little to no maintenance.
How to Tell a Refractor From a Reflector
What’s the difference between a refractor and a reflector that you can tell them apart by just glancing at them? The obvious one is the location of the focuser and the eyepiece.
The reflector has the focuser and eyepiece at the front (or the top), while the refractor is at the back of the telescope tube. Check out the image at the top of this article, you’ll notice this difference, with the one on the right, the reflector and the telescope on the left, the refractor.
But what about performance? Cost? And, how easy are refractors vs reflectors telescopes to use? The following shows these differences at a glance. But it really depends on the size and quality of the scope. Pricewise you can get a consumer type 70mm refractor or reflector telescope for under 200, maybe well under. It’s when you’re wanting a decent telescope for planet viewing etc. that you’ll pay more.
I might add that generally the most common of the two among serious backyard astronomers is the reflector type. One reason – reflectors vs refractors gather more light, performing better in this regard as they go up in size.
The Reflector refractor telescope difference
|Refractor||Uses a lens|
Eyepiece at rear
Eyepiece at front
Gathers more light
Cleaning of mirrors and tube
Can be subject to dust and humidity
You can find out more about why reflectors need collimating in my article that covers how to collimate a Dobsonian.
Reflecting telescope vs refracting telescope
What is a Refracting Telescope?
Refractors are dioptric, which simply means they use refraction. They have convex lenses.
The lens bends or refracts light. Compare this to a reflecting telescope where mirrors reflect light.
These types have the lens at the front and the eyepiece at the rear. They have a long, closed tube in which the light must travel in a straight path through to the eyepiece. The larger the lens the longer the tube needed. Hence, why refractors tend to be small.
They are known to suffer from chromatic aberrations, meaning colored fringes around the viewed objects. The other issues are spherical aberrations and lens sag.
Look for telescopes with compound lenses (different types of glass) to correct color aberrations. Doublets are less costly, but triplets are designed to eliminate this issue.
Parabolic lenses correct spherical abberations.
Lens sag becomes a problem with increased size. It only occurs in larger refractors. Here, the lens becomes distorted by its own weight.
For astrophotography, apochromatic refractors are said to be best as they overcome the need for an extra field corrector or space.
What is a reflecting Telescope?
Reflectors are catoptric, which simply means they use reflection.
They use one or more curved mirrors, which makes them free from chromatic aberrations.
Reflectors collect more light than refractors.
Most reflecting telescopes have a smaller secondary mirror. They have the eyepiece at the front and a tube that is open. The mirrors mean that the tube can be shorter.
Also, as the image is reflected upside-down a finderscope is needed to help locate the object in the sky. Most reflectors come with finderscopes.
Reflecting telescopes can suffer from aberrations (other than chromatic) and contrast issues.
They do need regular collimation and cleaning. So they require more maintenance than refractors.
They are better for viewing galaxies.
Cheaper reflectors have spherical mirrors.
Cassegrains are also used in amateur astronomy. I cover the Schmidt-Cassegrain type in my article on Orion vs Celestron Cassegrain Telescopes.
Reflector vs refractor vs catadioptric Telescopes
As the name suggests, catadioptric telescopes use both lenses and mirrors. There are many variations to these. They include the Maks and the SCTs. My guide on using telescopes to view planets gives the pros and cons of some popular examples of these.
Because of their compact design, the catadioptric telescopes are more portable than the typical reflector. But, like reflectors, they need collimation, though far less frequently. They can stay aligned and may only need collimation every few years.
The catadioptrics are versatile, being great for deep sky use as well as for viewing planets and the moon.
What is the difference between a reflector and a Refractor Telescope
Watch this video for more detail…
Are refactors better than reflectors?
In some respects they are. With the same aperture size, they give brighter and higher resolution images. Thus, you should get sharper images of stars and better contrast images of planets.
They are good for viewing the planets and the moon.
But, size is limiting with lens sag becoming an issue and these are not preferred by professionals.
Why are reflectors better than refractors?
Reflectors collect more light than refractors. Reflectors are better for viewing deep sky objects such as galaxies.
While refractors may give clearer views, reflectors are considered more user-friendly.
They are also better on the wallet.
Upkeep of Reflectors vs Refractors Telescopes
The hardest part of the upkeep of a reflector is cleaning the mirror while trying to avoid scratches. Fine scratches even can be worse than dust for messing with views.
Maintaining a reflector involves collimation. The bigger the objective in the reflectors, the greater the need for collimation. In cases of larger reflectors, this could be every time you move it to a new location. But with the right tools and practice, it will only take you 10 mins or so.
What’s involved with collimation? Collimation is the aligning of the primary with the secondary mirror and the eyepiece. You can do this manually or with the use of collimation tools. I explain how to collimate an SC telescope in my step by step account.
At the end of the day, it depends on what you intend using your telescope for, your budget, and whether you can physically manage the scope (where will you store it or do you need to transport it. All of the telescope types have their advantages and disadvantages.
Main image credits: ID 2306640 © Njnightsky and ID 169501910 © Johnypan | Dreamstime.com