Best Refractor Telescopes

Refractor telescopes are an excellent choice for deep sky astrophotography and beginning visual astronomy. Learn more about which refractor is right for you!

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What is a Refractor Telescope?

Refractors are the simplest type of telescope, and use glass lenses to magnify and focus incoming light. Refracting telescopes are one of the three main categories of telescopes, with the other two being Reflector Telescopes and Catadioptric Telescopes. Refractors were the first type of telescope to be invented in the year 1608.

 

How do Refractor Telescopes work?

Refracting telescopes work by using glass lenses to bend light into focus. The process of bending light is called refraction, hence their name. Light enters through the front of the telescope, passes through the tube, and then exits through the rear to an eyepiece or camera.

A diagram showing the light path of a refractor telescope. Light enters through the front, passes through glass lenses, and then exits through the rear of the telescope. Finally, the passing light is focused through an eyepiece or into a camera.

A doublet (two lens) refracting telescope. Image courtesy of Celestron.

 

Different Types of Refracting Telescopes

Refracting telescopes come in a wide variety of types, sizes, and prices. When looking at buying a refractor, you’ll see terms like doublet, triplet, chromatic aberration, achromatic, and apochromatic (or apo) used to describe them. It’s important to understand what these terms mean when buying a refracting telescope.

We’ll dive into what these terms mean below to help you decide. First, here’s a quick overview of the different types of refractor telescopes if you’re in a hurry:

 

Achromatic Doublet

Apochromatic Doublet

Triplet

Quadruplet / Petzval

Number of lenses

2

2

3

4+

Best Use

Budget visual astronomy

Budget imaging & visual observing

Imaging & visual observing

Imaging

Price Range

$

$$

$$ - $$$$

$$ - $$$$

 

Achromatic Doublet Refractor

Best for: beginners, kids, and adults on a budget | $

An image of an achromatic doublet refractor telescope, more specifically a Celestron StarSense Explorer LT 80AZ App-Enabled Refractor Telescope.

Celestron StarSense Explorer LT 80AZ App-Enabled Refractor Telescope

 

Pros: Achromatic doublets are the least expensive kind of refractor and least expensive telescope type overall. Using a simple design of just two lenses, these telescopes are extremely beginner friendly. Not only are they affordable, but they are also very portable.

Their design often folds up small, and a few models even fit into a backpack. Almost all achromatic doublet refractors come with a tripod mount, an eyepiece or two, and anything else you need to get started.

Cons: Achromatic doublet refractors will suffer from significant chromatic aberration — or unnatural color fringing — around bright stars, planets, and the Moon. To some picky experienced observers or imagers, this can be a dealbreaker. Since these are budget telescopes, they sometimes come with poor quality components like a wobbly tripod. Don’t expect to take great images with these telescopes, but you can still use a smartphone adapter to take good pictures of the Moon.

Shop Achromatic Doublet Refractors

 


Apochromatic Doublet Refractor

Best for beginner astrophotographers and imagers on a budget | $$

An image of an Apochromatic Doublet Refractor Telescope, more specifically a William Optics ZenithStar 81mm f/6.9 Doublet Apo Refractor.

William Optics ZenithStar 81mm f/6.9 Doublet Apo Refractor with Soft Case

 

Pros: A significant jump up in optical quality from achromatic doublets, an apo doublet will provide a very nice image. These telescopes are our top pick for a beginner astrophotography telescope. Although these telescopes aren’t completely free of chromatic aberration, they still produce great images that can rival some lower end triplets. 

Chromatic aberration can be mitigated with careful post processing, so many budget-conscious imagers opt for these telescopes and get great images out of them. You can also use these telescopes visually, but most are rather small.

Cons: Unlike most achromatic doublets, these apochromatic doublets rarely come with a tripod or eyepieces. This means you’ll need to purchase a mount separately, which can be just as much if not more than the telescope. Additionally, deep sky imagers will need to purchase a matching field flattener or reducer/flattener to produce round stars on today’s large sensor cameras. As already mentioned above, apochromatic doublets will still suffer from a small amount of chromatic aberration, making them inferior to true triplets.

Shop Apochromatic Doublet Refractors

 


Triplet Refractor

Best for serious deep sky astrophotographers and visual observers | $$ - $$$$

An image of an Apochromatic Triplet Refractor Telescope, more specifically a Sky Watcher Esprit 120mm ED Triplet Apo Refractor OTA.
Sky Watcher Esprit 120mm ED Triplet Apo Refractor OTA

 

Pros: As a true apochromatic refractor, a triplet can provide some of the best views and images of any telescope type. A high-quality triplet refractor is considered by some deep sky imagers to be the best telescope for astrophotography. This is because they fully correct for chromatic aberration and provide higher contrast images than reflector or catadioptric telescopes. As an added bonus, triplets also provide stunning visual views, though this is usually limited by their aperture.

Cons: The high quality of triplets means a high price tag. A quality 4” aperture triplet may cost as much or more as a 12” Newtonian reflector telescope. Astrophotographers also need to purchase a field flattener or reducer/flattener to produce round stars on images, which can be an expensive purchase in itself.

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Petzval Refractor

Best for dedicated wide field and deep sky astrophotographers | $$ - $$$$

An image of a Petzval Refractor Telescope, more specifically an Askar 107PHQ 107mm f/7 Quadruplet Flat-Field Astrograph.

Askar 107PHQ 107mm f/7 Quadruplet Flat-Field Astrograph

 

Pros: In today’s telescope world, the word Petzval has become synonymous with any telescope that uses four or more lenses. You will sometimes see a Petzval described as a quadruplet (four lenses), quintuplet (five lenses), or sextuplet (six lenses).

In a nutshell, any number of lenses beyond three are likely used to produce a flat field image for use in astrophotography. That means Petzvals come with a field flattener built into the optical design, which removes some added cost. With a field flattener built into the design, dialing in back focus is not required. Simply reaching focus is enough to produce a flat field image.

Cons: Unlike triplets and doublets, most Petzval refractors are exclusively designed for astrophotography and cannot be used visually. Like triplets, Petzvals are also generally expensive.

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What is Chromatic Aberration in a Telescope?

The quality of the view you get out of a refractor telescope is largely determined by the number of lenses used. Telescopes focus red, green, and blue (RGB) light to form an image. In theory, a perfect telescope focuses all of these colors at the same point. In order for that to happen, a refractor telescope must use three (or more) lenses.

Most beginner refractors are doublets. Since doublets only have two lenses, they can only focus two of the three RGB colors at the same time. This results in chromatic aberration, which is when you see unnatural color fringing around a bright star, planet, or the Moon. Chromatic aberration can be seen when visually observing through an eyepiece or in images when doing astrophotography.

Chromatic aberration degrades the view, but it is subjective. A beginner may not really notice or care much about chromatic aberration, and therefore a doublet is a perfectly good telescope to start with. On the flip side, experienced telescope users and astrophotographers will usually spend a bit more to buy a higher-end triplet refractor. Triplet refractors should not suffer from chromatic aberration.

 

Achromatic vs. Apochromatic (APO)

When shopping for a refractor, it’s important to understand the difference between achromatic and apochromatic. The term achromatic means that a telescope cannot bring all three colors into focus at the same plane — only two. That means that all doublet refractors inherently suffer from some level of chromatic aberration.

An apochromatic (or simply Apo) refractor can bring all three colors into focus at the same plane, and therefore does not have chromatic aberration. Triplet refractors, by design, should be apochromatic because their three lenses bring red, green, and blue to the same focal plane.

However, the number of lenses in a telescope isn’t the only factor that determines whether it is achromatic or apochromatic. The type of glass used and the coatings on the glass have a large effect on chromatic aberration as well. Some higher-end doublet telescopes will be branded as an “apo doublet.” This means that higher quality glass and/or coatings are used to minimize chromatic aberration more than a lower-end achromatic doublet.

On the other hand, some lower-end triplet refractors may skimp on using quality glass and/or coatings. This can sometimes result in chromatic aberration even in a triplet refractor, which should not have any. Therefore, some higher-end apochromatic doublet refractors can actually come close to matching the performance of a lower-end triplet.