Embarking on the journey of stargazing and astronomy can be thrilling. Choosing the right telescope for you is a crucial first step. Our guide is here to help you navigate the various types of amateur telescopes, ensuring you find the one that aligns with your astronomical interests and lifestyle.
We’ll explore popular choices like refractors, reflectors, and catadioptric telescopes. Each type comes with its unique features and capabilities, suitable for different observing preferences.
Note that our focus is strictly on amateur models. We won’t be delving into professional giants like the James Webb Space Telescope or large radio telescopes. Additionally, solar telescopes are reserved for a dedicated article, highlighting their specialized nature. This guide is your beacon in the cosmos of amateur astronomy, helping you make an informed decision.
As a new telescope user, familiarizing yourself with key terms will enhance your understanding and enjoyment of astronomy. Here are some essential terms:
Aperture: The diameter of the primary (biggest) lens or mirror of a telescope. It determines how much light the telescope can gather, directly impacting its ability to see faint objects.
Collimation: The alignment of the mirrors in a reflector telescope or the lenses in a refractor. Proper collimation is crucial for optimal image quality.
Eyepiece: The part of the telescope you look through. Eyepieces come in different focal lengths, affecting the magnification and field of view.
Field of View: The area of the sky visible through the telescope at any given time.
Finderscope: A small, low-power scope mounted on the main telescope. It helps in locating objects in the sky before viewing them through the main telescope.
Focal Length: The distance between the telescope’s primary lens or mirror and the point where the light rays come together in focus. This is the measure that the magnification and field of view of the telescope rely on.
Mount: The structure that supports the telescope. There are two main types: alt-azimuth (simple, up-down and left-right movement) and equatorial (aligned with Earth’s axis, allowing smooth tracking of stars as they move across the sky).
Optical Tube Assembly (OTA): The telescope’s “body”, the tube that collects light in at one end and houses lenses and/or mirrors at one (or both) ends to focus it
Resolution: The ability of a telescope to distinguish fine details and separate close objects.
Armed with these terms, that will help you navigate the world of telescopes more effectively, let’s jump into answering what are the different types of telescopes.
The Three Main Telescope Types
In amateur astronomy, the three main types of telescopes are:
– Refractors: Utilize lenses to bend and focus light, known for their sharp, high-contrast images.
– Reflectors: Employ mirrors to gather and focus celestial light, offering larger apertures for deeper sky exploration.
– Catadioptric: Innovative hybrids that combine lenses and mirrors, providing compact and versatile viewing experiences.
We’re going to look at these in more detail in the following sections, exploring the pros and cons of each type.
An Introduction to Refractor Telescopes
A refractor telescope uses lenses to gather and focus light, allowing you to see distant celestial objects. At its simplest, it consists of a long tube (known as the optical tube assembly, or OTA) with a glass lens at the front (the objective lens) and an eyepiece at the back.
This design is celebrated for its sharp, high-contrast images, and because it’s sealed from the elements, it requires little maintenance.
There are two key types of refractor telescopes: achromatic and apochromatic.
Achromatic Refractors: These are the more common and affordable type of refractor. They use two glass elements in the objective lens to reduce chromatic aberration, which is a type of distortion that creates color fringes around bright objects. While achromatic refractors significantly reduce this effect, they don’t eliminate it entirely.
Apochromatic Refractors: These are the premium cousins of achromatic refractors. They typically use three or more glass elements in the objective lens, which drastically reduces chromatic aberration, resulting in clearer and sharper images with true-to-life colors. However, the level of precision manufacturing that goes into creating a ‘triplet’ lens means they are very expensive, which is why apochromats are favored by serious hobbyists and astrophotographers.
Pros and Cons of Achromatic Refractors
Achromatic refractors hold several advantages, making them an attractive choice for new astronomers:
1. Ease of Use: Achromatic refractors are generally very user-friendly. They come with a simple design that’s easy to set up and use, making them ideal for beginners.
2. Durability and Low Maintenance: The sealed tube design of refractors protects the optics from dust and other contaminants. This makes them durable and requires minimal maintenance compared to other types of telescopes, like reflectors which may need regular alignment (known as collimation) and cleaning.
3. Good Optical Quality: Despite some level of chromatic aberration, achromatic refractors typically provide sharp and contrasted images. They are especially good for viewing the Moon, planets, and double stars, where their high resolution enhances the viewing experience.
4. No Obstructions in the Optical Path: Unlike reflector telescopes, which have a secondary mirror that can obstruct some light, refractors have an unobstructed path for light to travel. As in the point above, this results in sharper images with better contrast.
5. Portability: Many achromatic refractors are compact and lightweight, especially those with smaller apertures. This portability makes them a great option for astronomers who plan to travel with their telescope or have limited storage space.
6. Cost-Effective: Compared to apochromatic refractors, achromatic models are more affordable, offering a balance of quality and price. This makes them a great entry-level option for those who want a decent telescope without a hefty price tag.
7. Versatility: Achromatic refractors are versatile and can be used for a variety of astronomical observations, including star clusters, nebulae, and other celestial objects, in addition to planetary and lunar viewing.
8. Predictable Performance: The refractor’s design leads to predictable and consistent performance. There’s no need to collimate (align) the optics, a process often required for reflector telescopes.
For a new astronomer, an achromatic refractor offers a great mix of simplicity, performance, and value. It’s a straightforward, dependable, and enjoyable way to start exploring the night sky.
While popular among beginners and budget-conscious astronomers, achromats do come with some inherent disadvantages:
1. Chromatic Aberration: Although they reduce chromatic aberration compared to single-lens systems, achromatic refractors don’t eliminate it entirely. This can be noticeable when observing bright objects like the moon or planets, where color fringes often appear at the edges.
2. Limited Aperture: Achromatic refractors are often limited in size (aperture). Larger apertures gather more light and offer better resolution, but making large, high-quality lenses for refractors is challenging and expensive. This size limitation can impact the telescope’s ability to observe fainter objects.
3. Weight and Size: The lenses in refractor telescopes, especially larger ones, can be heavy and bulky. This can make the telescope less portable and require a sturdier (and often more expensive) mount to hold it steady.
4. Cool Down Time: Glass lenses in refractors can take some time to adjust to the outside temperature (thermal equilibrium). This is more noticeable in larger lenses and can affect the telescope’s performance during the initial period of observation.
5. Cost: While achromatic refractors are generally more affordable than their apochromatic counterparts, they can still be more expensive than reflector telescopes of similar aperture size. The cost increases with the quality and size of the lenses.
6. Too Cheap: Being budget conscious is great but often manufacturers are cheap when it comes to accessible refractors. The mount, eyepieces and finderscope supplied with the main telescope are, frankly, nasty, and reduce the enjoyment of astronomy. They’re also a false economy as you’ll need to upgrade them for a better experience.
7. Limited Contrast: Due to residual chromatic and spherical aberrations, achromatic refractors might not provide as high contrast in the images as apochromatic refractors or quality reflectors. This can affect the viewing experience, especially for planetary and lunar observation.
Despite these drawbacks, achromatic refractors are still a great entry point into astronomy. They offer good image quality for their price and are low maintenance, making them suitable for beginners or those looking for a simple, “grab-and-go” telescope.
Pros and Cons of Apochromatic Refractors
Apochromatic refractors share some characteristics with achromatic refractors, but they also have unique advantages and disadvantages:
1. Superior Chromatic Aberration Correction: Apochromatic refractors use advanced lens designs, often with special glass or multiple elements, to significantly reduce chromatic aberration. This results in clearer, sharper images with truer colors, especially around bright objects like stars and planets.
2. Better Image Quality: Due to their superior optical design, apochromatic refractors generally offer sharper and higher contrast images than achromatic refractors, making them excellent for astrophotography and detailed planetary viewing.
Both of these reasons are why they are often the go-to design for astrophotographers.
1. Higher Cost: Apochromatic refractors are significantly more expensive than achromatic models. The specialized materials and complex lens designs contribute to their higher price.
2. Weight: Apochromatic refractors can be heavier than achromats of similar size due to the use of denser glass types in their construction. This may require sturdier (and often more expensive) mounts. A superior mount is also required to deliver great astro-images.
In summary, while apochromatic refractors share some pros and cons with achromatic refractors, their key distinctions lie in superior image quality and color correction, balanced against a considerably higher cost and potentially greater weight.
Both types of refractor telescopes are excellent for beginners, with achromatic being more budget-friendly and apochromatic offering superior image quality. Your choice depends on your interests, particularly how important astrophotography is (or will be) to you, and how much you’re willing to invest in your stargazing journey.
An Introduction to Reflector Telescopes
A Newtonian reflector uses mirrors instead of lenses. At its heart is a large, concave primary mirror at the opposite end of the OTA from the open end that gathers light.
This mirror captures light from the night sky and reflects it to a smaller, flat secondary mirror near the top. The secondary mirror then directs the light to the side of the telescope tube, where it’s focused into the eyepiece for viewing.
Pros and Cons of Newtonian Reflectors
1. Affordability: They offer more aperture (the diameter of the primary mirror) for your money compared to refractors. A larger aperture means more light-gathering power, essential for viewing faint objects like distant galaxies and nebulae.
2. Sharp Images: Newtonians provide crisp and bright images, excellent for both planetary and deep-sky observing.
3. Compactness: Despite their large mirrors, Newtonians are relatively compact thanks to their design, making them easier to store and transport.
4. Versatility: They are great for a variety of astronomical observations, from planets and the Moon to galaxies and nebulae.
Newtonian reflector telescopes, while offering many advantages, do have some disadvantages to consider, especially for new astronomers:
1. Collimation: All reflector telescopes require regular collimation, the process of aligning the mirrors. This can be a bit challenging for beginners, but it’s crucial for the best optical performance. It’s also nowhere near as scary as beginners anticipate (see our collimation guide).
2. Size and Weight: Larger models can be quite bulky and heavy. This can make transportation and storage a bit more challenging compared to smaller refractors or compact catadioptric telescopes.
3. Open Tube Design: The open tube of a Newtonian reflector can accumulate dust and debris more easily than the sealed tubes of refractors. This means they may require more frequent cleaning. Again, this is relatively straightforward and does not need doing as often as you might anticipate.
4. Difficulties in Observing at High Angles: When observing objects high in the sky, the eyepiece of a Newtonian can end up in awkward, hard-to-reach positions. This can make viewing less comfortable, especially for longer observations.
5. Optical Distortions: While the physics of mirrors means that these telescopes are free from chromatic aberration (color fringing), reflectors can suffer from coma. This is an optical distortion that makes stars appear comet-like near the edges of the field of view, especially in faster (lower f/number) [link to fast and slow] telescopes.
6. Thermal Equilibrium: Large mirrors can take time to reach thermal equilibrium with the surrounding air. Until they do, image quality can be adversely affected.
Despite these drawbacks, Newtonian reflectors remain a popular choice due to their excellent price-to-aperture ratio, making them ideal for beginners who want to explore deep-sky objects without a large investment.
For even more value for money, think about buying a Dobsonian-style telescope, which is what we’ll look at next.
A Dobsonian telescope is a type of Newtonian reflector, which means it uses mirrors to gather and focus light. The primary distinction of a Dobsonian lies in its mount, not its optical system. So, when we talk about Dobsonian telescopes, we’re really talking about the kind of mount that the OTA comes equipped with.
The Dobsonian mount is a low-cost, easy-to-use, alt-azimuth design. It allows the telescope to move up and down (altitude) and left and right (azimuth). This straightforward movement makes it intuitive for beginners to navigate the night sky. The mount is usually made of wood or other sturdy materials and sits directly on the ground, offering stability and ease of use.
Since very little of the cost of a Dob is in the mount, much more of your purchase price goes towards the OTA. This is why Dobsonian telescopes are known for delivering affordably priced large apertures, making them excellent for observing faint deep-sky objects like galaxies and nebulae. Their simple design doesn’t compromise performance, offering bright and clear images.
In essence, a Dobsonian telescope combines the effective light-gathering capability of a Newtonian reflector with a user-friendly, cost-effective mount, making it an ideal choice for new astronomers eager to explore the wonders of the night sky.
Pros and cons of Dobsonian Telescopes
Dobsonian telescopes are a popular choice for beginners in astronomy, and like any telescope design, they have their own set of pros and cons:
1. Affordability: One of the biggest advantages of Dobsonian telescopes is their affordability. They offer a large aperture at a lower cost compared to other telescope types.
2. Simple to Use: The Dobsonian mount is renowned for its simplicity. It moves up and down (altitude) and left and right (azimuth), making it intuitive and straightforward for beginners to navigate the night sky.
3. Large Aperture: Dobsonians typically have large mirrors, providing a substantial light-gathering capacity. This allows for better observation of faint deep-sky objects like galaxies and nebulae.
4. Stability: The Dobsonian mount is low to the ground and robust, offering great stability, which is crucial for clear viewing.
5. Easy Setup: These telescopes require minimal setup and alignment, which can be particularly appealing for beginners.
Size and Portability: Dobsonian telescopes can be quite large and heavy, especially those with larger apertures. This can make them less portable and more challenging to store.
Limited Astrophotography Use: Due to their basic mount design, Dobsonians are not ideal for long-exposure astrophotography. They lack the motorized tracking capabilities required for capturing detailed images of celestial objects over extended periods.
Maintenance: The mirrors may require regular collimation (alignment), especially after transporting the telescope. As we mentioned above though, this is not a good argument for avoiding this kind of telescope; collimation is not as complicated as it sounds!
Low Altitude Limitations: Observing objects near the horizon can be difficult due to the design of the mount.
Manual Tracking: For the same reason Dob’s don’t work for astrophotography, they also need manual adjustment to keep objects in view as they track across the sky. This might be challenging for some beginners, but many astronomers love this element of the hobby.
In summary, Dobsonian telescopes are excellent for beginners due to their ease of use, affordability, and great light-gathering ability. However, considerations regarding size, portability, and suitability for certain types of astronomy should be taken into account when choosing this type of telescope.
An Introduction to Catadioptric (Compound) Telescopes
Our final type of telescope is the catadioptric, also known as a compound telescope. This type is a blend of two different technologies, combining the best of both worlds from refractors (which use lenses) and reflectors (which use mirrors).
In a catadioptric telescope, light first passes through a corrector lens at the front. This lens helps to eliminate optical imperfections. The light then hits a primary mirror at the back of the telescope, which reflects it back up towards a secondary mirror. This secondary mirror, located near the front, reflects the light again, directing it through a hole in the primary mirror and into the eyepiece at the back.
This design allows catadioptric telescopes to be more compact and portable than other types with similar power. They are versatile, offering excellent views of both distant galaxies and nearby planets. Their closed-tube design also means less maintenance and protection from dust.
However, they tend to be more expensive than simple refractors or reflectors, especially as most models come with object-tracking motors and a computerized database of sights to look at. Also, the complex optical path can introduce some image distortions, and they may require some time to reach thermal equilibrium for optimal viewing.
Catadioptric telescopes are a great choice if you’re looking for a balance of portability, power, and versatility in your stargazing adventures.
Cat’s Have Long Focal Lengths in Short Bodies
The construction of a catadioptric telescope means the light covers a greater distance than the length of the telescope before it hits your eye, i.e. it has a longer focal length than its relatively short body implies.
The advantages of this are:
1. Portability: One of the main advantages is portability. Telescopes with long focal lengths typically require long tubes, making them bulky and difficult to transport. Catadioptric telescopes, with their clever design, pack a long focal length into a much shorter tube, making them more compact and easier to carry around.
2. Enhanced Magnification and Detail: A longer focal length allows for higher magnification, which is crucial for detailed observation of celestial objects like planets and the Moon. This means catadioptric telescopes can provide close-up views without the need for an excessively long and unwieldy tube.
3. Reduced Image Aberrations: The design of catadioptric telescopes often includes corrective optics, like a Schmidt or Maksutov corrector plate (the lens at the light-gathering end of the OTA), which help reduce optical aberrations. This results in clearer, sharper images.
4. Stability: A shorter telescope body is less susceptible to vibrations and wind, leading to more stable and clearer viewing experiences. This stability is especially important for astrophotography.
5. Ease of Mounting: Shorter tubes are easier to balance and mount on both alt-azimuth and equatorial mounts. This makes setting up and using the telescope simpler, which is beneficial for beginners and seasoned astronomers alike.
In essence, the design of catadioptric telescopes with longer focal lengths in shorter bodies provides an excellent combination of portability, detailed observation capabilities, and ease of use, making them a popular choice among amateur astronomers.
On top of that, there are other upsides to owning a compound telescope:
Pros of a Catadioptric Telescope
1. Versatility: These telescopes are well-suited for both planetary and deep-sky observations. Their high focal ratios make them excellent for detailed views of planets and the Moon, while their ability to gather ample light allows for observing fainter objects like galaxies and nebulae.
2. Closed Optical System: The tube is sealed, which protects the optics from dust, dirt, and dew. This leads to less frequent cleaning and maintenance compared to open-tube designs like Newtonian reflectors.
3. Astrophotography Compatibility: Many catadioptric telescopes are well-suited for astrophotography. Their long focal lengths and stable platforms are ideal for capturing detailed images of celestial objects. However, you may need to use a corrector wedge to make sure your scope is at the right angle, e.g. on the NexStar SE range.
4. Thermal Stability: The closed tube design helps in maintaining thermal stability, reducing air currents inside the tube that can distort images. This is particularly beneficial for observing fine details on planets.
5. Slow Focal Ratios: Typically, catadioptric telescopes have slow focal ratios (f/10 or higher), which provide a wider, more forgiving field of focus. This is beneficial for beginners as it makes focusing easier and is more forgiving of minor errors in tracking or alignment.
6. Upgradeability: They often come with features that allow for easy upgrades, like computerized mounts or the ability to add GPS modules, making them a future-proof choice.
In summary, catadioptric telescopes are a versatile, maintenance-friendly, and upgradeable option, suitable for a wide range of astronomical observations and astrophotography, appealing to both beginners and experienced astronomers.
Cons of a Catadioptric Telescope
While catadioptric telescopes offer many benefits, there are also some drawbacks to consider:
1. Cost: This is the most important factor! Generally, catadioptric telescopes are more expensive than refractors or reflectors of similar aperture. The advanced optics, complex design, and tracking mounts with computerized databases all contribute to a higher price tag.
2. Cool Down Time: Due to their closed design, these telescopes can take longer to acclimate to the outside temperature. This is known as “cool down” time, and until the telescope reaches thermal equilibrium, image quality might be affected.
3. Weight and Bulk: Despite their compact length, catadioptric telescopes, especially larger models, can be quite heavy. This is due to the dense glass and mirror components. The weight might make them less portable and may require a sturdier mount.
4. Maintenance of Collimation: While less frequent than with Newtonian reflectors, catadioptric telescopes still require collimation (alignment of the optics). This process can be more complex and intimidating for beginners than in a standard reflector.
5. Narrow Field of View: The long focal length of catadioptric telescopes typically results in a narrower field of view compared to other types. This can make it more challenging to locate objects and is less ideal for wide-field astrophotography.
6. Optical Limitations: Some models may suffer from optical issues such as field curvature or require additional corrector lenses for optimal imaging, particularly in astrophotography.
In summary, catadioptric telescopes offer a blend of advanced features suited for both novice and experienced astronomers. They excel in versatility, equally adept at planetary and deep-sky observation. Compact and portable, these telescopes bring powerful optics in a manageable size, ideal for those with limited space.
However, this comes with a higher price tag compared to simpler designs. Their weight, while contributing to stability, can affect ease of transportation. Additionally, they require a period of cool-down to reach thermal equilibrium for optimal viewing and occasionally need collimation to maintain their precise optics.
Despite these considerations, catadioptric telescopes are favored for their balance between quality and practicality. With a narrower field of view and some optical limitations, they still stand out as a top choice for those seeking a versatile and high-quality astronomical experience in a relatively compact package.
In exploring the world of amateur astronomy, we’ve delved into five distinct types of telescopes, each with unique attributes catering to different stargazing preferences. Use this summary to work out which might be the best for you to begin your astronomy journey with.
Achromatic Refractors: These telescopes are ideal for beginners due to their simplicity and ease of use. They offer good optical quality and require minimal maintenance, making them a hassle-free choice for starting your astronomical journey. Their standout feature is their user-friendliness, offering a straightforward introduction to astronomy.
Apochromatic Refractors: Known for their superior image quality, apochromatic refractors significantly reduce chromatic aberration, providing clearer and sharper images. They are the best choice for those who prioritize high-quality, true-to-color views of the night sky, and for whom budget isn’t an issue.
Newtonian Reflectors: Offering better value for their size, Newtonian reflectors provide large apertures at an affordable price. This makes them ideal for observing faint deep-sky objects like galaxies and nebulae. They are perfect for astronomers who want to explore more of the universe without a large investment.
Dobsonian telescopes: These are ideal for beginners, offering a blend of simplicity, affordability, and impressive light-gathering ability. Their easy-to-use Dobsonian mount provides straightforward sky navigation, making them perfect for newcomers and anyone trying to maximize their budget.
Catadioptric Telescopes: These telescopes blend the best of refractors and reflectors, offering compactness and versatility. Their standout advantage is the combination of portability and powerful optics, making them a great all-around choice for diverse astronomical pursuits. Their databases and tracking make them a must-have choice for astronomers who want to see the views without having to track them down first.
If you’d like to take the next step, try our telescope picker to get some ideas for your first telescope.