Perhaps you’ve been thinking about taking up the fun hobby of stargazing, but you’re not quite sure which telescope would be the best one to use. The two most common types of telescopes on the market are reflector and refractor telescopes, but what exactly are they, and how do they differ? Below is a description of each type of telescope to help you determine which one would be the best fit for your needs.
As its name implies, a reflecting telescope utilises curved mirrors in order to reflect the observed image back to your eye. Simply put, a reflector reflects.
Although these types of telescopes can vary in size and complexity, the basic makeup of the instrument is the same: There is a bowl-shaped (concave) mirror positioned at the bottom of the telescope, and a large opening at the other end that allows light to enter. Once the light bounces off the bowl-shaped mirror, it gets reflected to a secondary mirror, and then sent to the eyepiece, which is where you’ll put your eye in order to observe the target image.
One of the most famous examples of a reflecting telescope is the Hubble Telescope, which weighs roughly 27,000 pounds and features a mirror that is nearly eight feet in diameter!
While magnification plays a significant role in the reflecting telescope’s power, the main key behind its effectiveness is the fact that it can collect far more light than the human eye. The size of the mirror plays a key role in determining how much light is collected; as you can imagine, a larger mirror can collect more light, and this captured light is then magnified by way of the eyepiece.
- Highly cost-effective when compared to similarly-sized reflector telescopes due to lower cost of manufacturing mirrors vs. lenses
- Good portability due to its compact size
- Offers better viewing of distant stars and galaxies with larger aperture sizes
- Brighter delivery and less distortion of observed images
- No chromatic aberration (a.k.a. “colour fringing”) because its mirrors reflect all wavelengths in the same manner
- It can be difficult to keep the optics in alignment
- Can experience a little bit of light loss due to the use of a second mirror
Credit: Szőcs Tamás via Wikimedia
Refracting telescopes differ from reflecting telescopes in that they use lenses instead of mirrors to gather and project light to the eyepiece. So instead of reflecting the light, refractors bend the light to accomplish their purpose.
If you can imagine those old pirate movies where the captain of the ship is looking out across the sea using a “spyglass”, that can give you a basic picture of what a refractor telescope looks like.
The earliest telescopes were refractors, as are the typical telescopes you’ll find in department stores. Refracting telescopes are known for producing sharp, precise images, and they’re typically smaller and more lightweight than their reflecting counterparts.
- Simple, straightforward design that is very user-friendly and reliable
- Excellent viewing experience for observing the stars, the moon and other planets
- Lenses are permanently aligned and mounted, which means little to no maintenance for you
- Sealed tube structure helps reduce image degradation
- Highly portable
- Fantastic terrestrial viewing
- Sharp, high-quality color rendering of observed images
- Images appear right-side-up, making this telescope an excellent choice for daytime viewing (e.g., bird watching, etc.)
- All refractors suffer from some degree of chromatic aberration, which can produce a purple or rainbow-coloured haze around the image; this is due to the varying wavelengths of light being bent by the lenses at different rates
- Lenses for refractor telescopes are more expensive to produce, which means that refracting telescopes typically carry a higher price tag than similarly-sized reflecting telescopes
As you can see, both telescopes have their particular merits as well as their disadvantages.
For the beginning stargazer, the most commonly recommended telescope is the refractor for a couple of key reasons:
- First, refractor telescopes are self-contained units that require virtually no maintenance or adjustments. By contrast, reflector telescopes require relatively regular adjustments to the mirror, not unlike how guitars need to be tuned on a frequent basis.
- Second, the very low-maintenance nature of the refractor telescope makes it a much more portable companion for all types of on-location observations.
Please keep the above points in mind, so that you can make a sound, well-informed buying decision. Happy stargazing!