If you’re new to astronomy, you might wonder what are the two types of telescopes. The answer is fundamental to understanding how every telescope works. At their core, all telescopes are designed to do two things: collect light and magnify an image. But the way they achieve this splits them into two main categories. Knowing these types helps you choose the right tool for your stargazing journey. It’s the first step in bringing distant galaxies, planets, and nebulae into clearer view.
This guide will explain the two primary designs. We’ll look at how they function, their key advantages, and their typical uses. You’ll learn which type might be best for your needs and budget. We’ll also cover some important sub-types and key features to consider. Let’s begin with the basic principle that seperates them.
What Are The Two Types Of Telescopes
The two fundamental types of telescopes are refracting telescopes and reflecting telescopes. The difference lies in how they gather and focus light. A refractor uses a glass lens at the front of the tube. A reflector uses a curved mirror at the back of the tube. This single design choice leads to all their other differences in performance, maintenance, and cost.
Refracting Telescopes: The Classic Design
A refracting telescope, or refractor, is what most people picture when they think of a telescope. It has a long, straight tube with a large objective lens at the front. This lens bends (refracts) incoming light to a focus point near the back of the tube. An eyepiece lens then magnifies this focused image for your eye.
The design is simple and sealed, which means it requires little maintenance. The tube is not open to the air, so dust and moisture rarely get inside. The optics also tend to stay in alignment (collimated) for long periods. This makes refractors very user-friendly, especially for beginners.
Key Advantages of Refractors
- Sharp, High-Contrast Images: Refractors excel at providing crisp views of the moon and planets. Their sealed design and lack of a central obstruction (like a secondary mirror) create images with high contrast.
- Low Maintenance: With no mirrors to adjust and a closed tube, they are largely “set it and forget it” instruments.
- Durability: The optical assembly is rigid and less prone to going out of alignment if bumped.
- Excellent for Terrestrial Viewing: Their design naturally produces an upright image, making them great for birdwatching or daytime use with the correct diagonal.
Common Drawbacks of Refractors
- Chromatic Aberration: This is a color fringing effect, where different colors of light focus at slightly different points. It can cause purple halos around bright objects like the moon. Higher-quality “apochromatic” (APO) lenses correct this, but they are expensive.
- Size and Cost for Aperture: Large, perfect glass lenses are very difficult and costly to manufacture. A refractor with a 4-inch lens can be much longer and more expensive than a reflector with the same light-gathering power.
- Generally Longer Tubes: For a given focal length, the tube must be at least that long, which can make larger models cumbersome.
Reflecting Telescopes: The Mirror-Based Powerhouse
A reflecting telescope, or reflector, uses mirrors instead of lenses. The primary mirror, a large concave mirror at the bottom of the tube, collects light and reflects it back up. A smaller, flat secondary mirror near the top of the tube then angles the focused light out to the side, where the eyepiece is located. This design is most associated with Sir Isaac Newton, so you’ll often hear them called Newtonian reflectors.
Because light doesn’t pass through the mirror, only its surface needs to be perfect. This makes large mirrors much more affordable to produce than large lenses. For this reason, almost all major research telescopes and the largest amateur telescopes are reflectors.
Key Advantages of Reflectors
- More Aperture for Your Money: This is the biggest benefit. You can get a much larger light-gathering mirror for the same price as a smaller refractor lens. More aperture means you can see fainter objects like galaxies and nebulae in greater detail.
- No Chromatic Aberration: Mirrors reflect all colors of light the same way, so there is no color fringing. Images are naturally color-accurate.
- Compact Design for Focal Length: By folding the light path, a reflector can have a long focal length in a relatively short tube.
Common Drawbacks of Reflectors
- Regular Maintenance: The open tube can collect dust, and the mirrors can go out of alignment (require collimation). You may need to learn to adjust them occasionally.
- Central Obstruction: The secondary mirror blocks a small portion of incoming light, which can slightly reduce contrast compared to a similar-quality refractor.
- Image Orientation: The image is often upside-down or mirrored, which is fine for astronomy but requires an extra erecting lens for terrestrial use.
Comparing Refractors vs. Reflectors: A Quick Guide
So, which type is right for you? Here’s a simple breakdown based on common priorities:
- For Planetary and Lunar Viewing: A high-quality refractor (especially an APO) often gives the sharpest, highest-contrast views. A good reflector with a long focal length can also perform excellently.
- For Deep-Sky Objects (Galaxies, Nebulae): A reflector with its larger aperture wins here. It collects more light from these faint, diffuse objects.
- For Beginners Seeking Ease of Use: A small to medium refractor is often recommended due to its low maintenance. However, many beginners successfully start with a popular reflector like a Dobsonian (see below).
- For Astrophotography: Both types are used, but refractors (especially APOs) are popular for their sharp, contrasty images and compactness. Reflectors offer great light grasp for deep-sky imaging but may be bulkier.
- For a Tight Budget: Reflectors provide the most aperture per dollar, letting you see more for less money.
Important Sub-Types and Hybrids
While refractors and reflectors are the two main families, there are important sub-types and hybrid designs that combine elements of both.
Catadioptric Telescopes: The Best of Both Worlds?
Catadioptric telescopes use a combination of lenses (correcting plates) and mirrors. The two most popular designs are the Schmidt-Cassegrain (SCT) and Maksutov-Cassegrain (Mak). Light enters through a thin corrector lens at the front, bounces off a primary mirror in the back, then off a secondary mirror (often attached to the corrector), and finally out through a hole in the primary mirror to the eyepiece.
Advantages: They pack a very long focal length into an extremely compact and portable tube. They are versatile for both visual observing and astrophotography. The closed tube reduces maintenance.
Disadvantages: They are generally more expensive than Newtonian reflectors of similar aperture. They have a narrow field of view compared to many refractors and shorter reflectors.
The Dobsonian Mount: A Game Changer for Reflectors
This isn’t a new optical design, but a brilliant, simple, and affordable mounting system for Newtonian reflectors. A “Dobsonian” telescope is a Newtonian reflector on a sturdy, easy-to-use alt-azimuth rocker box. The savings from the simple mount are put into a very large aperture mirror. For visual observing of deep-sky objects, a Dobsonian offers the most light-gathering power per dollar of any telescope type.
Key Features to Look at Beyond the Type
Knowing the two types is crucial, but other specs are equally important when choosing.
Aperture: The Most Important Spec
Aperture is the diameter of the primary lens or mirror. It determines how much light the telescope can collect. More light means brighter, clearer, and more detailed views. A larger aperture will always show you more than a smaller one, regardless of type. Prioritize aperture within your budget and portability needs.
Focal Length and Focal Ratio
The focal length is the distance light travels inside the scope to come to focus. It affects magnification and field of view. The focal ratio (focal length divided by aperture, written as f/4, f/10, etc.) indicates the telescope’s “speed.”
- Lower f/numbers (e.g., f/4 to f/5): “Faster” scopes. They provide wider fields of view and are excellent for observing large deep-sky objects. They are also preferred for deep-sky astrophotography due to shorter exposure times.
- Higher f/numbers (e.g., f/10 to f/15): “Slower” scopes. They provide narrower fields of view but higher magnifications, which is good for planets and the moon. They are also more forgiving on simpler eyepieces.
The Mount: Your Telescope’s Foundation
A wobbly mount ruins the view. There are two main types:
- Alt-Azimuth (Alt-Az): Moves up-down (altitude) and left-right (azimuth). Simple and intuitive, like a camera tripod. Dobsonian mounts are a type of Alt-Az mount.
- Equatorial (EQ): Aligned with Earth’s axis, it allows you to track celestial objects smoothly with a single motor. Essential for long-exposure astrophotography but has a steeper learning curve.
Getting Started: Practical Recommendations
Based on all this, here are some common starter recommendations:
- For a Child or Absolute Beginner: A small (70mm-90mm) refractor on a simple tripod. It’s easy to set up, use, and maintain.
- For a Beginner Serious About Deep Sky: A 6-inch or 8-inch Dobsonian reflector. It offers stunning views of faint objects for a very reasonable price and is simple to operate.
- For a Beginner Interested in Planets & Portability: A 4-inch or 5-inch Maksutov-Cassegrain (Mak). It provides sharp, high-magnification views in a very compact tube.
- For an Enthusiast Interested in Astrophotography: A small apochromatic refractor (70-80mm APO) on a sturdy equatorial mount with a motor drive. This is a more advanced and costly starting point, but it’s purpose-built for imaging.
Remember, the best telescope is the one you’ll use regularly. Consider where you’ll store it, how you’ll transport it, and your local viewing conditions (like light pollution). A smaller, easy-to-use scope that gets used often is better than a huge, complex one that stays in the closet.
Caring for Your Telescope
Proper care ensures great views for years to come.
- Always let your telescope acclimatize to the outside temperature before use to avoid tube currents that blur images.
- Use lens caps and dust covers when not in use.
- Clean optics only when absolutely necessary, and reseach proper methods first. A little dust rarely affects performance.
- For reflectors and catadioptrics, learn how to check and gently adjust collimation.
- Store your telescope in a dry, stable environment.
FAQ Section
What are the 2 main types of telescopes?
The two main types are refracting telescopes (which use lenses) and reflecting telescopes (which use mirrors).
Which type of telescope is best for a beginner?
Many beginners do well with a Dobsonian reflector because it offers a lot of power for a low price and is simple to use. A small refractor is also a great, low-maintenance choice for casual stargazing.
What is better a reflector or refractor telescope?
There’s no single “better” type. Reflectors generally give you more aperture for your money, making them great for faint deep-sky objects. Refractors often provide sharper, higher-contrast views of planets and the moon and require less maintenance. Your goals and budget determine which is better for you.
Can I see planets with a reflector telescope?
Absolutely. A good quality reflector, especially one with a longer focal length, can provide spectacular views of planets like Jupiter, Saturn, and Mars. The key is having enough aperture and good atmospheric conditions (steady “seeing”).
What is the most common type of home telescope?
For visual observers, the Newtonian reflector on a Dobsonian mount is arguably the most common serious amateur telescope due to its excellent value and performance. In the past, small refractors were the most common entry-level scopes.
Are catadioptric telescopes good?
Yes, they are excellent and very popular. Their compact size and long focal length make them versatile all-rounders, suitable for both visual observing and astrophotography. They are a bit more expensive than Newtonians of similar aperture but offer great convenience.
Understanding what are the two types of telescopes gives you the foundation to make an informed choice. Whether you choose the lens-based path of the refractor or the mirror-powered path of the reflector, each opens a unique window to the universe. Start by considering what you most want to see, how much you want to spend, and how much complexity you’re comfortable with. Then, get ready for a lifetime of wonder under the stars. Clear skies!