I’m sometimes asked to compare a Dobsonian Telescope vs Newtonian. This comparison doesn’t make sense to me. It would be like asking which one is better, a bowl of soup or eating dinner. Let me explain what I mean.
The word Newtonian refers to only one type of telescope, and the term Dobsonian refers to a specific bundling of things, which includes a Newtonian telescope. It’s like eating dinner that consists of a bowl of soup, but the dinner is a complete meal, a specific bundling of things, not just one bowl of soup.
To properly use a telescope, you must place it on a mount. You can’t just use a telescope right out of the box. Well, not effectively, anyway.
Please note that when I say telescope, I’m referring to the long tube with glass or mirrors inside. Telescope means to look at things carefully (“scope,” as in to scope out a room) that are very far away (“tele-,” as in television, telephone, or telegram).
I’m separating the telescope from the rest of the bundle of things that make up a complete package on purpose because it’s essential for you to understand it in the context of what a Dobsonian is.
A more accurate word, or phrase, to describe the tube I keep referring to that has lenses or mirrors inside it is the Optical Tube Assembly.
A Newtonian is a type of optical tube assembly, and a Dobsonian is a complete package, an optical tube assembly, and a mount. In other words, a complete package, like a dinner.
I can understand the confusion in asking Newtonian vs Dobsonian telescope. People sometimes throw around terms without realizing they’re misusing them.
I want to help you understand the various terms related to telescopes, including mounts. You can place multiple types of telescopes on top of different mounts.
Each complete package serves a unique purpose. You can configure each package in a way that works best for you.
You will soon be in an excellent position to understand why asking Dobsonian vs Newtonian doesn’t make much sense.
However, you’ll also understand why it’s a good question. I will help you figure out which telescope and mount best meet your needs.
In this article, you get
To reframe what is meant by Dobsonian vs Newtonian Telescope
A look inside how different types of telescopes work
A comparison of popular mounts and their specific purpose
An understanding of telescope optics and options
By the end of this article, you’ll be able to determine Newtonian telescope vs Dobsonian, and the best mount for your needs.
Let’s dive right in.
WHAT IS A DOBSONIAN TELESCOPE?
To be able to answer this question, we first need to understand who John Dobson was and why he invented a new type of telescope.
John Dobson was an American amateur astronomer.
In the early 1960s, Dobson became involved with the San Francisco Sidewalk Astronomers, a group of amateur astronomers who set up telescopes on city sidewalks to share their love of astronomy with passers-by.
Dobson developed a simple design for a telescope that used inexpensive materials. This low-cost method made them an ideal choice as one of the best beginner telescopes.
The telescope can be moved up and down and side to side. This design, known as the Dobsonian Telescope, revolutionized amateur astronomy by making it possible for anyone to build a high-quality telescope. It also had a very large aperture and jokingly became known as a “light bucket” because it gathered so much light.
Dobson continued to build and refine his telescopes throughout his life. He also traveled around the country, giving talks about astronomy and demonstrating his telescopes to anyone interested. He died in 2014 at the age of 98.
Now that you know who John Dobson was and why his invention became popular, let’s look at what a Newtonian is. This will help you compare a Dobson vs Newtonian.
WHAT IS A NEWTONIAN?
The Newtonian reflecting telescope is the most popular type of amateur telescope.
The Newtonian telescope uses a concave mirror to reflect light and produce an image. A thin layer of silver or aluminum usually coats the mirror’s reflecting surface.
The advantage of Newtonian reflector telescopes over other types of telescopes is their simplicity and low cost. They’re also easy to construct and use.
A Dobsonian and a Newtonian are both low-cost, easy to use, and popular with amateur astronomers.
The Dobsonian is the whole package, a telescope (optical tube assembly), plus a mount.
The Newtonian, however, is just the optical tube assembly, which is only one part of the complete package.
I want to dive deeper into each of these two things so that you understand the fundamentals of both telescopes and mounts.
And for an even more in-depth look at Newtonians, read my article What is a Newtonian Telescope?
First up, the various telescope types.
There are three main telescope types, refractors, reflectors, and catadioptrics.
A refracting telescope is an optical tube assembly that uses a lens to gather light and form an image.
Dutch eyeglass maker Hans Lippershey invented the first refractor telescope in the early 17th century. Italian scientist Galileo Galilei improved the design.
To learn more about early refractor telescope design, read my article Keplerian vs Galilean Telescope.
Refracting telescopes are typically much smaller and more portable than reflecting telescopes, making them great first telescopes for amateur astronomers.
However, they have some drawbacks. Most notably, the lenses can suffer from “chromatic aberration,” which causes colors to appear fringed or distorted.
A reflecting telescope uses mirrors to reflect and magnify an image.
Sir Isaac Newton built the first reflecting telescope in 1668.
Newton’s design used a curved mirror to reflect light through a hole in the front of the telescope, which allowed him to see distant objects more clearly than with a refracting telescope.
The advantage of a reflecting telescope over a refracting telescope is that it can be made much larger for the same amount of money. Reflecting telescopes also don’t suffer from chromatic aberration.
One disadvantage of reflecting telescopes is that they require precise alignment of the mirrors to work correctly. Moving the telescope can disrupt this alignment, so most reflecting telescopes are mounted on sturdy stands or platforms to minimize movement.
Reflecting telescopes are popular with amateur astronomers because they are ideal for gathering faint light from distant objects, like nebulae, galaxies, and other deep-sky objects.
A Catadioptric telescope is a compound telescope that uses both lenses and mirrors to correct for optical aberrations. They also pack a long focal length into a small package.
Catadioptric telescopes are usually more expensive than refractive telescopes, but they offer superior image quality.
The most common type of catadioptric telescope is the Schmidt-Cassegrain telescope, which uses a combination of a concave mirror and a convex lens to form an image.
Maksutov-Cassegrain telescopes are a type of reflector telescope first conceived in the early 19th century by Russian optician Dmitri Maksutov.
The key feature of the Maksutov telescope is the corrector plate, a concave meniscus lens placed in front of the primary mirror. This corrector plate is what gives the telescope its unique shape.
If you’re wondering about the word Cassegrain, here’s what you need to know.
The Cassegrain reflector is a telescope that uses a concave mirror to focus light from a distant object onto a small secondary mirror, which then reflects the light through a hole in the primary mirror. This design allows for a shorter length for the telescope while providing good image quality. Laurent Cassegrain invented this design in 1672.
By the way, to learn more about telescopes, read my article Refractor Telescope vs Reflector. And if you’re curious about image orientation, read my article Why is my telescope upside down? For a bit of fun, you can read my article DIY Solar Filter Telescope.
Now, I’d like to switch to mounts because, as I mentioned above, these telescopes are only effective with a good mount.
There are two main types of mounts, but I’ll also mention go-to systems and the Dobsonian mount.
An alt-az mount is a telescope mount that uses altitude and azimuth axes to point the telescope.
You can use this mount for both terrestrial and astronomical observation.
The main advantage of an alt-az mount over other mounts is its simplicity. No polar alignment is required, making it easier and faster to set up.
Alt-az mounts are also less expensive than other types of mounts.
An equatorial mount is a mount for a telescope with one rotational axis parallel to the Earth’s axis of rotation.
This type of mount is necessary for astronomical observing and astrophotography because it allows the telescope to rotate in sync with the Earth’s rotation.
This tracking movement keeps celestial objects in view during long-exposure photography.
Amateur astronomers use the term “GoTo” to refer to a type of telescope mount and related software that automatically points a telescope at astronomical objects.
The mount for this type of telescope is controlled mainly by a computer, and both axes require a motor.
Some GoTo mounts keep track of where they’re pointing, even if you move the telescope by hand.
A Dobsonian mount is a simple but effective design for an alt-azimuth mount created by John Dobson in 1965.
It is popular among amateur astronomers and telescope makers because it is inexpensive and easy to build and use.
A base and a telescope tube make up the Dobsonian mount.
The base is usually circular or square-shaped and has three or four legs. The telescope tube is attached to the base and can be moved up and down and left to right. You can easily point the telescope at different objects in the sky.
To recap this section and highlight the main difference between the mounts.
An altazimuth mount is low-cost, easy to use, and suitable for visual observation.
An equatorial mount is more complex to set up, but it is required to take long night sky exposures for astrophotography.
Go-to systems help you find your target in the sky. They aren’t required but are helpful.
Now that I’ve detailed the various types of telescopes and mounts, I’d like to dive even deeper into telescopes. You’ll get to understand some crucial elements to help you decide what best suits your needs.
THE PURPOSE OF TELESCOPES
Before diving too deep, let me first explain the purpose of telescopes in basic terms.
The purpose of telescopes is to collect and focus light from distant objects to produce magnified images.
You can then see things that would otherwise be too faint or too small to be seen with the naked eye.
Telescopes come in a variety of designs, each optimized for different tasks. For example, some telescopes are better for viewing planets and stars, while others are better for observing distant galaxies. For more info about viewing planets, read my article Can You See Planets With A Telescope?
To help you decide what best meets your needs, let’s first look at the most crucial thing: the telescope’s optics.
ACHROMAT VS. APOCHROMAT
For refractor telescopes, you will need to understand achromatic and apochromatic. What’s the difference between the two?
Achromatic telescopes use a lens made of two different types of glass. The first type of glass refracts blue light, while the second type refracts red light.
This combination helps to reduce chromatic aberration, which is when colors appear fringed or blurred at the focal point.
Achromatic lenses are typically less expensive than apochromatic lenses. However, the image is not as clear.
Apochromatic telescopes use a lens made of three different types of glass. The first type of glass refracts blue light, the second type refracts green light, and the third type refracts red light.
This combination helps to reduce chromatic aberration even further, providing a more precise image than an achromatic telescope.
Apochromatic lenses are more expensive, but they’re worth the investment if you’re serious about astronomy.
So, which type of telescope is better? That depends on your needs.
If you’re doing general night sky observations, an achromatic telescope will be just fine.
However, an apochromatic telescope is a better choice if you want to do serious astrophotography or study faint objects.
The focal ratio of a telescope is the ratio of its focal length to its aperture. In other words, it measures how “long” the telescope is.
The larger the focal ratio, the longer the telescope and the higher the magnification. The smaller the focal ratio, the shorter the telescope and the lower the magnification.
So, what focal ratio should you choose? It depends on what you want to use your telescope.
You will need a long-focal-ratio telescope if you’re going to do high-magnification work, such as planetary or double-star observing. For example, read my article Can You See Saturn With A Telescope? For more info on magnification, read my article about how Barlow lenses work.
You will need a short-focal-ratio telescope to do wide-field work, such as observing star clusters and nebulae.
In general, beginner astronomers should choose a medium-focal-ratio telescope (around f/5) because it balances magnification and field of view.
As you become more experienced, you can experiment with different focal ratios to see which works best for your needs.
The word “magnification” gets thrown around a lot when discussing telescopes. But what is magnification? And how do you choose the right telescope for your needs?
In its simplest form, magnification is the power of a telescope to make an object appear larger than it is with the unaided eye. But there’s more to it than that.
The amount of detail you can see in an object also depends on the telescope’s aperture or the diameter of its primary lens or mirror. A bigger aperture means more light-gathering power, better resolution, and more detailed images.
So, when choosing a telescope, keep the magnification and aperture in mind. A good rule of thumb is that the minimum useful magnification is two times the aperture in inches (or three times in centimeters). So, for example, if you want to see fine details on Jupiter, you’ll need at least a 4-inch (10-cm) telescope. For more info on Jupiter, read my article How To Find Jupiter With a Telescope.
Of course, there are always trade-offs. A bigger telescope will be more expensive and more difficult to transport and set up. So it’s essential to find the right balance for your needs.
SIZES OF TELESCOPES
The type of telescope you need depends on your specific needs and interests.
When it comes to telescopes, there is no one-size-fits-all answer.
However, you can follow some general guidelines when choosing a telescope.
Small telescopes typically have an aperture size of 3 inches or less, making them more portable and accessible to set up than large telescopes.
A medium telescope has a larger aperture of 10 to 16 inches.
These telescopes are ideal for viewing the Moon, planets, and bright stars but may not provide the level of detail and clarity needed for observing deep-sky objects.
Medium telescopes are a good choice for general use. They provide a good balance between light-gathering power and portability. They are also suitable for astrophotography, as they can capture decent images of planets and galaxies. For example, read my article Can You See Mars With A Telescope?
If you are interested in observing nebulae and galaxies, you will need a larger telescope with a bigger aperture. On the other hand, if you want to focus on bright objects like the Moon and planets, then a smaller telescope will be sufficient.
As a general guide, a large telescope typically has an aperture of 10 inches (25 cm) or more.
This size aperture allows for significant light-gathering power and resolution, making it ideal for observing faint objects such as galaxies and nebulae. It could also resolve more minor details on brighter objects such as planets.
Large telescopes can be costly, so it is worth considering what you hope to observe before making a purchase.
After reading this article, hopefully, you understand the differences between a Newtonian reflector vs Dobsonian. A Dobsonian is a “complete package” and a Newtonian is a “telescope.”
A Dobsonian might be your best bet if you’re looking for an easy-to-use telescope package that’s great for beginners.
However, if you’re looking for something with more power, then a Newtonian reflecting telescope, a refractor, or even a Cassegrain might be what you need. With these options, however, you must choose a mount.
You can take long-exposure photos of things like the Andromeda Galaxy with an equatorial mount.
Whether you choose a Newtonian or Dobsonian telescope, do your research so that you end up with the right one for your astronomy goals.
FREQUENTLY ASKED QUESTIONS
ARE DOBSONIAN TELESCOPES BETTER?
Dobsonian telescopes are very good and are a popular choice for amateurs and professionals alike. They’re also economical when it comes to other types of telescopes. The optical part of the telescope, the optical tube assembly, is the same as a Newtonian telescope.
IS A DOBSONIAN GOOD FOR VIEWING PLANETS?
Aperture is one of the most important factors in Dobsonian telescopes, and larger apertures tend to produce brighter and more contrasted images. A large aperture is particularly good for revealing surface detail in planets like Jupiter or Saturn.
CAN YOU TAKE PHOTOS WITH A DOBSONIAN TELESCOPE?
No. For long-exposure astrophotography of deep-sky objects, you’ll need an equatorial mount. However, photographs of the Moon and planets are possible.
HOW DO YOU AIM A DOBSONIAN TELESCOPE?
A Dobsonian telescope requires that you manually move the telescope tube left or right according to where your target is located. Turn the slow-motion control knobs on the mount using both hands, but only when viewing through the eyepiece. To use the slow-motion control knobs, first, locate your object of interest in the eyepiece and then slowly turn one hand clockwise and one hand counterclockwise.
CAN YOU USE A DOBSONIAN TELESCOPE FOR TERRESTRIAL VIEWING?
No, telescopes used for observing the night sky flip the image, which is perfect for astronomy but unacceptable for terrestrial viewing.