Refractor vs. Reflector Telescope: Which is Better?
There are two main types of telescopes: the refractor and the reflector. They are fundamentally different in design as the refractor telescope is composed of convex lenses to collect, direct, and magnify light, whereas the reflector uses concave mirrors. They also differ in their viewing purpose, durability, portability, and monetary value.
In the early 1600s, Galileo created the first modern-day prototype of a telescope using two lenses, a hollow tube, and an eyepiece at the end. Most likely, if you were to picture a telescope in your mind, you’re imagining the refractor telescope, and the classic design hasn’t changed too much since its inception.
Pros & Cons:
A refractor telescope is an excellent choice if your primary viewing purpose is planets and the moon. Because the telescope has a closed design that blocks air and dust from moving through the scope the result will be clear, crisp images that also make it a great option if you plan on getting into astrophotography. Refractor telescopes tend to be quite rugged and will travel well. Unlike their reflector counterparts, they never require collimation (realignment of the mirrors) which tends to be a big selling point for telescope novices.
No telescopes are without their flaws, however. If you want a telescope with a larger aperture (which will collect more light and allow you to see fainter objects), a refractor telescope will end up being quite pricey. Another pain-point is that refractor telescopes have something called chromatic aberration. As light passes through the primary lens it breaks up into its color components just as a prism casts a rainbow on the wall by breaking white light into its various colors. In short, you may notice some color fringing around the objects you’re observing. The lower the focal ratio of the optical tube the more chromatic aberration you are likely to see although it can be reduced with the use of achromatic and apochromatic lenses. Apochromatic (or “triplet”) refractors are designed to eliminate chromatic aberration but they are a much heavier and more expensive option.
Not long after Galileo invented the refractor telescope, Sir Isaac Newton developed the reflector telescope, largely as a response to the chromatic aberration found in the former. Newton eliminated the chromatic aberration through the use of concave mirrors rather than lenses to collect light and form an image.
Pros & Cons:
As mentioned, one of the biggest benefits of the reflector telescope is the elimination of the pesky color fringing. If you desire a larger aperture, reflectors are a much more cost-efficient option as mirrors are cheaper to manufacture than the refractor lenses. The big aperture that is accessible in reflectors makes these telescopes perfect for deep-sky observations – such as far away galaxies and nebulae.
Where the refractor telescope has fixed lenses, the mirrors in reflectors will require regular collimation. Collimation only takes a few minutes and is simple once you’ve done it a few times, but the maintenance sometimes deters new astronomers. Reflectors also have an open-ended tube design so keep in mind that dust can gather in the scope and will need to be cleaned. Lastly, the reflector can have an aberration called a coma which appears to be spiky light diffractions around your objects. This can typically be eliminated with a separate coma corrector lens.
It'd be wrong of me not to mention the third main type that came about in the late 1800s – the catadioptric (or compound) telescope. The catadioptric telescope combines the best features of the refractor and the reflector in one. Catadioptrics have the benefit of a larger aperture with a lightweight optical tube which makes it easy to transport. Due to the lens/mirror combination design, catadioptrics are free of almost all coma and chromatic aberrations.
The biggest drawback of catadioptrics? The cost. They tend to be significantly more expensive than refractors and reflectors, and thus may not be the best option starting out. The images they present are also less bright than other scopes of similar aperture and power.
Between the different types, there is no "perfect" design. In the end, it largely depends on your primary viewing purpose, how much you want to spend, and how large of a telescope you want to carry with you.
For first-time buyers, was this information helpful for you? And if you already own a telescope, imagine you're making your first purchase all over again - would you do it the same?
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