Beginners Guide to Newtonian Telescope – Clarity Scopes

Your Guide to Newtonian Telescope

Have you ever dreamed about becoming an astronaut and going into space? You can still get a closer look at the stars and the celestial bodies. Telescopes are devices that can make that happen!

This article focuses on a Newtonian telescope. It's a device type that uses mirrors to produce images. This guide offers more details on its components. You'll discover the major parts and benefits of using these units. Keep reading to see if this product is your best choice!

What Does Newtonian Telescope Mean?

Jake Lippershey invented this device in the 17th century. It was a refraction telescope, and it used lenses as optical components. These units remain in use today and are popular among beginners.

It didn’t take long for Isaac Newton to develop another product type. The English physicist made construction with mirrors to collect the light and deliver the picture. The Newtonian unit became the first reflecting telescope.

The technology improved component quality. The manufacturers have access to better and more durable parts. The actual design of reflection units didn’t change much. You’ll still notice the original Newton’s construction to secure an impressive image quality.

What Can You Use the Newtonian Telescopes for?

These devices primarily serve for astronomy and celestial viewing. That means you can observe stars, planets, galaxies, and other bodies. The construction is optimal to get you a close-up image of those objects.

You can use Newtonian units for terrestrial observation. They aren’t the most suitable choice. You might encounter problems sharpening the image when viewing land-based objects. If there are no other options, use this telescope to watch distant items. Otherwise, think about refraction products since they are more suitable for the purpose.

How Do You Use a Newtonian Telescope?

You can purchase a premium product that delivers a fantastic performance. It won't value much if you don't understand how to use it. Newtonian devices have a specific working process. Here is a simple explanation of how they deliver the image.

  1. The primary mirror collects the light received by the observed items.
  2. This component sends the light to the second glass.
  3. It reflects the picture to the eyepiece. You use that component to see the picture.

The optical components are ones that deliver the images and allow observing. Here is more information about the main parts.

Primary Mirror

This is the primary glass component in Newtonian telescopes. That makes it essential for the device’s working process. The part’s specifics include:

  • It’s in the tube’s lower section.
  • The common shape is paraboloidal or spherical.
  • The manufacturers often aluminize the surface. They use an adjustable cell and place the mirror inside. That ensures optimal support without the component deforming.
  • It has an optical axis that’s crucial for fine-tuning and optimal positioning.

Here is the information about the primary mirror’s working process:

  1. It collects light as it passes through the pipe. That serves for creating an image at the focal level.
  2. The focal point is the location where the image is sharpest and brightest.
  3. You find that spot to align your device. Other positions might have aberration that worsens the image quality. You might notice asymmetry or blurriness. That doesn’t happen when the adjustment is optimal.

Secondary Mirror

This is another optical component, and you'll find it on the tube's front. The primary mirror creates the image, and this unit moves it to the pipe's primary side. You'll find this piece is often small. The idea is that the focal plane's center can get light from the entire main part.

The secondary mirror offers multiple adjustments. The idea is to ensure that the best image quality is in the eyepiece's center. This component uses an adjustable holder and attaches the piece with a spider. It's often a thin metal that forms a cross, but the construction varies.


The final optical component of a Newtonian reflector observation unit is the eyepiece. As the word suggests, you use it to see the image of the monitored objects. This is essentially a lens with advanced magnifying capabilities.

Once the image forms in other components, the eyepiece allows viewing it. The component features an optical axis. You'll often notice the picture isn't perfect at the edges. That's a common problem, especially at entry-level units. It’s crucial to see everything sharply in the center. That will ensure you can see the observed bodies in their full power.

What Are the Main Advantages of Newtonian Telescopes?

Why would you use these devices, and what’s the reason for their popularity? If that's your questions, look at these units' benefits:

  1. It doesn't have issues with chromatic aberration. This is a frequent downside with refraction telescopes. The reflection units don't deal with this, and they secure an aberration-free image.
  2. The devices can be quite affordable. The Newtonian type has a simple construction. Today's technology allows easy access to components. That secures a tempting price for these units, especially entry-level products.
  3. It features a wide field of view. You'll require a unit with a short focal ratio. If you find it, you can enjoy this benefit. That will ensure you see more of the observed area.
  4. It's not difficult to make. This is another reason why manufacturers don't increase the price tag. They need to polish a single mirror surface, which is an advantage of modern Newtonian designs.
  5. It has excellent portability. The Newtonian telescope mirror is at the tube's bottom. You'll find the eyepiece at the top. That ensures a compact design and makes the product easy to transport.

Does This Telescope Have Downsides?

No product is perfect, and that also applies to this category. The actual drawbacks depend on the unit. A Celestron Newtonian telescope is different from other brands. Here are the general disadvantages that these units face:

  1. These products have problems with off-axis aberration. The result is that the image's edge might become blurry or distorted. That's why you should go with primary mirrors with a low focal ratio.
  2. The secondary mirror could cause a central obstruction. If the component is in the light path, users could notice reduced contrast. The solution could be a spider with two or three legs.
  3. Do you have a portable reflector unit? Those telescopes often have issues requiring frequent adjustment. You'll need to align the components to ensure optimal image delivery.

Main Characteristics to Analyze When Selecting Newtonian Telescopes


Beginners often think that all telescopes are similar. These devices have different features. Here are the characteristics to consider when selecting a unit.


The experts believe this is a critical specification. That's because it indicates the mirror's diameter. It describes the potential of capturing light and ensuring a sharp image. This characteristic is important for picture brightness.

Aperture comes with proportionate capabilities. Does your telescope have a large diameter? It will have a better celestial object image than small units. The standard is around 80 millimeters.

This is all about suitability. Beginners might find a low-diameter mirror enough. Advanced users could require a bigger aperture. That allows them to observe more distant objects. A larger option could be more expensive. This component affects the price significantly.


The idea of what a telescope does tells enough about its magnification potential. The moon is a small circle in the sky when observed from the ground. Using this device allows getting a closer look at celestial bodies. You can see bumps and other specifics and watch them in full power.

The magnification standard is around 50x. That means 50 more times than the aperture in inches. The premium units can have a 200x zooming capability. However, optimal adjustment is essential. It’s not only about using maximum available settings. You might face image distortion at high levels. 


Newtonian telescopes are compatible with various mount types. The selection will depend on your expertise. Here is the crucial information about available options:

  • Dobsonian. The most common mount in Newtonian telescopes is this type. It places the head on the ground. That's why it requires Teflon for the expected stability.
  • Equatorial. This is another option suitable for tracking celestial objects. They move across the sky, and you use the knob to adjust the mount. Some units come with automatic monitoring.
  • Alt-az. These mounts are the simplest to use. You can only move them in two directions. The first is up-down, and the second from left to right. The adjustments needed are minimal. That makes them suitable for beginners.

Other Characteristics

Aperture, mount, and magnification are crucial for Newtonian telescopes. Other important features can affect the device's performance. Those include:

  • Focal length. This describes the length from the image to the primary mirror. The standard is up to 3,000mm. A minimum of 400mm is necessary for optimal performance.
  • Eyepieces. This component's size is important for magnification. You'll usually find these have 10-25mm. You can divide the focal length with this measurement to determine magnification.
  • Focal ratio. You'll notice an "f/X" description. The "X" stands for a number. The lowest is usually "4." Those units have the widest field of view. An alternative is the "f/15" setting. The experts recommend approximately f/7 to observe star clusters and galaxies.

Component Quality

The manufacturers usually maintain a high material quality when designing Newtonian telescopes. The glass used for the mirrors is crucial. It shouldn't have any imperfections as they could affect the image. An aluminized mirror surface contributes to overall durability. The construction should be stable and long-lasting. Thanks to that, the product should serve you well for years.


The cost goes together with the desired performance. Entry-level units are cheaper, and they can meet beginners' preferences. These devices often serve entire families. They can provide much fun during camping and field trips.

Premium telescopes have a higher price tag. You use them to observe deep space, galaxies, and distant bodies. These take additional adjustments, so they come with a learning curve.

How to Align a Newtonian Reflector Telescope

The alignment process isn't difficult. It only involves three steps. Make sure you are patient since some constructions require dexterity. If the telescope is large, you could need a helping hand. Here is what to do to adjust the device!

Step 1: Centering the Secondary Mirror

The initial step involves aligning this component with the focuser. You can use a sight tube for this step. Position it inside the focuser, and then observe the secondary mirror.

You should place the unit in the tube's center. If you have issues doing that, try adjusting the secondary holder. Find the bolt that connects it to the spider. Modify its position by moving it away or to the primary mirror.

Step 2: Place the Eyepiece in the Mirror's Center

Grab the secondary reflecting unit's tilt. Adjust it until the axis is at the primary center. The initial step involves checking the spider and removing the cardboard. Use the sight tube and adjust the screws. The goal is for the reflection of the primary component to be in the field of view's center. You can also use a laser collimator.

Step 3: Find the Best Spot

This is the crucial step, so arm yourself with patience. The goal is to move the primary mirror to the focuser's center. You can use a special eyepiece that goes into the focuser. You can adjust the reflection by modifying the screws.

You want to adjust the mirror before each observation session. If the temperature changes significantly, you might need to modify it occasionally. The same applies if more people use the telescope. That increases the odds of the components going out of position.

Final Thoughts

The Newtonian design offers something different than the classic refraction telescope. It uses a different approach and forms images with mirrors. These optical components deliver fantastic picture quality and impressive durability.

If you'd like to try reflection devices, you can't go wrong with a Newtonian telescope. This unit is easy to use and offers a wide field of view. Thanks to it, you can enjoy celestial bodies to their full potential!