Trying to select between a refractor and a reflector telescope can be confusing. Reflecting telescopes have unique advantages over refracting telescopes, but the opposite is also true. How can you know which telescope is best for you?
We’re not just astronomy buffs; we’re telescope nerds. On a clear night, you can find many of us with our telescopes aimed at the night sky in search of that perfect view. We’ll give you the low down on which type of telescope best suits your needs, and we might even save you some expensive buyer’s remorse, too.
Join us as we break down everything you need to know about refractor and reflector telescopes to choose the best one for you!
Refractor vs. Reflector Telescope: Side-by-Side Comparison
| Refractor Telescope | Reflector Telescope | |
|---|---|---|
| Optical Lenses? | Yes | No |
| Optics | The light is redirected and focused with a lens | Mirrors focus and bend the light |
| Mirrors? | No | Yes |
| Image | Upright display | The display is upside down and inverted. An additional lens is required to display with the proper orientation. |
| Best use | Deep space | Moon and planets |
| Maintenance? | Yes, open system | No, closed system |
| Chromatic Aberration? | Yes | No |
| Spherical Aberration? | No | Yes |
| Cost | More expensive | Less expensive |
| Size | Lighter, smaller | Heavier, bigger |
Refractor vs. Reflector Telescope: What’s the Difference?
It’s easy to become overwhelmed when it’s time to evaluate a refractor telescope and a reflector telescope. It’s important that you don’t ignore the critical differences between the telescope types. One size doesn’t necessarily fit all.
Let’s take a look at each type of telescope.
Refractor Telescope
A refractor telescope collects light through an optical lens. The optical lens bends and focuses the light after it enters the telescope. The image is magnified and displayed on an optical eyepiece. A refracting telescope is perfect for deep space observation (DSO).
Refracting Telescope Invention
In 1608, Hans Lipperhey created the refracting telescope for land surveying and military use.
Lipperhy, a spectacle-maker with lens grinding experience, placed two convex lenses into a cylinder. Lipperhy’s design put a large collection lens at one end of the cylinder. The design called for a smaller secondary lens to be located at the center of the opposite end of the cylinder. Lipperhy’s telescope is called the “Danish perspective glass.”
In 1609, Galileo Galilei modified Hans Lipperhey’s telescope design and added a 3x magnification lens. Galileo continued to fine-tune the convex lens grinding process. Ultimately, Galileo reached 30x magnification from the modified lens.
Once the magnification improved the telescope’s capability, it became a popular option for astronomers to direct into the night skies instead of fields of battle.
©Miroshnichenko Tetiana/Shutterstock.com
How Does a Refractor Telescope Work?
Refractor telescopes collect more light when the collection lens is large. A bigger lens is better for collecting very faint light. As the size of the collection lens increases, so does the length of the telescope.
Light enters a refracting telescope through a large convex lens. The curvature of the convex lens forces the light to bend toward the telescope’s center. The light travels through the telescope in a continually tightening to-center path until it reaches the point of convergence and passes through the focal plane. At the focal plane, a virtual image is created. The virtual image is based on whatever object the telescope points at, like a distant galaxy.
A convex lens greets light into the telescope, and a concave lens ushers the light out. A concave lens, the eyepiece, reverses the light constriction. The convex lens “shrunk” the image, and the concave lens reverses the compression and expands the picture.
The eyepiece is mechanically adjusted to bring objects into focus. Focusing the eyepiece moves it closer or further away from the virtual image created with the convex lens.
Reflector Telescope
Unlike refracting telescopes, reflecting telescopes don’t use a series of lenses. A reflector telescope uses mirrors instead of lenses to focus the light entering the telescope. Eliminating heavy optics decreases the telescope’s weight and reduces the cost. A reflector telescope is a good choice for viewing the moon or planets.
©milosgagic/Shutterstock.com
Reflector Telescope Invention
In 1663, a Scottish astronomer and mathematician, James Gregory, published his design for a reflecting telescope. Gregory’s design allowed a telescope to use a series of mirrors instead of an optical lens. The use of mirrors instead of lenses altogether avoided the challenge of optical lenses, namely chromatic aberration.
In 1668, Isaac Newton used James Gregory’s reflector telescope design and built a functional telescope with mirrors instead of optical lenses.
How Does a Reflector Telescope Work?
Named after their inventor, Issac Newton, reflector telescopes are often called “Newtonians.” A reflector telescope uses mirrors instead of a lens to direct and shape the light — the open design of a reflector telescope results in the need for periodic cleaning of the telescope interior. Mirror defects cause defocus or distortion in the final image.
Light enters a reflective telescope through the end of the telescope. Unlike the reflecting telescope, the reflective telescope doesn’t have a convex lens to direct light toward the center of the lens. Instead, light travels through the telescope body until it reaches a parabolic mirror at the far end of the telescope.
The mirror reflects and directs the light toward the far end of the telescope where the light entered. The shape of the parabolic mirror redirects the light, similar to the convex lens in a refractor telescope, converging toward the telescope’s center.
The light strikes a second mirror and reflects towards the eyepiece. The image is turned upside down and inverted.
Light enters the eyepiece after being reflected by a mirror inside the reflector telescope’s main body. The eyepiece is mechanically adjustable to correct for focus.
Collimation
Reflector telescopes require collimation. Collimation is a mechanical alignment process to align the telescope mirrors to correct for focus on the eyepiece properly. You’ll know if you must collimate if you cannot focus correctly and your images are blurry. (Not to worry, collimating a telescope is relatively simple.)
©luchschenF/Shutterstock.com
Refractor vs. Reflector Telescope: 10 Must-Know Facts
- Determine if you plan to use the telescope for astrophotography. Taking images of the moon or planets in our solar system differs from images of far-off galaxies.
- A refractor telescope is a good selection for moon and planet observation.
- A reflector telescope is best suited to deep-space observation. Deep space observations are galaxies or nebulae. (A DSO isn’t a planet or another solar system.)
- If you’re targeting astrophotography, a refractor telescope is your best friend.
- A refractor telescope requires collimation.
- Certain types of refractor telescopes may require periodic cleaning of the mirrors.
- A lens generally seals reflective telescopes on each end of the telescope body. The lens on each end “seals” the telescope from dust, humidity, and debris. You may still need to clean the inside of the telescope, but that’s an exception, not a rule.
- A refractive telescope (which contains an optical lens) is generally cheaper than a reflective telescope (which includes mirrors).
- A reflector telescope is an ideal place to start if you’re new to astronomy. It’s easier on the bank account than a refractive telescope. If you like astronomy, invest in a more expensive telescope. If you don’t like astronomy, you’re not out quite so much cash.
- Practice with your telescope during daylight hours. Learning the locations of buttons, knobs, and switches is easier during daylight hours.
Refractor vs. Reflector Telescope: Which One is Better?
You can spend tens of thousands of dollars on a telescope you use once a year. We suggest spending less on a telescope and using it more often.
As the complexity and cost of a telescope increase, we’re more prone to leaving the telescope stationary and using it less often. There’s a lot of value in an inexpensive telescope that you can toss in the back seat of the car and take camping for a weekend.
A reflective telescope is a good choice for a weekend adventure when you’re mobile and searching for a great view from a local park or dark area, and it’s suitable for deep space observation, like galaxies and nebula.
A reflective telescope will require that you collimate the mirrors. It’s not rocket science; you’ll learn how to knock this task out quickly. A reflective telescope can be used for the moon and planets, but the image may be better from a refractive telescope.
A refractive telescope rarely requires collimation, so it’s a good choice if you’re cautious of collimation, and it’s best suited to observation of the moon and planets. Reflective telescopes are also less expensive than refractive telescopes.
The image featured at the top of this post is ©Vadim Sadovski/Shutterstock.com.
