Dobsonian Telescope Advantages and Disadvantages

A Dobsonian is the best beginner telescope according to many amateur astronomers. Why? There are a few reasons why they are popular for beginners and advanced users alike. One main appeal is that the design is cheaper for the power it offers. They are also simple to use. Here we weigh up the Dobsonian telescope advantages and disadvantages to help you decide on their value.

John Dobson is credited with inventing this telescope design during the 1960s. This optical instrument first became popular in the 1970s in northern California. Published articles helped the popularity of the design grow and due to its ease of use and relatively low cost, today, it is one of the most common telescope designs available.

Are Dobsonian telescopes good for viewing planets?

A Dobsonian can give you awe-inspiring views of planetary details as well as lunar features. You’ll get to see the polar caps on Mars, the rings of Saturn, and the moons and bands of Jupiter with a 6″ Dobsonian given the right viewing conditions.

It is this reason that you’ll find them mentioned in our buyer’s guide to the best telescopes for planet viewing.

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why get a Dobsonian?

If you ask a Dob user, they’ll say Dobsonians are less frustrating to use than the more sophisticated types. Dobs are a larger scope but are easy to take out and set up. They are also easy to use and more stable than those mounted on tripods (which tend to shake when touched). 

With a Dobsonian, you can quickly set up and point your telescope at the Moon or other bright objects in the sky and enjoy decent views on any night with the right observing conditions.

See also: Best Time For Stargazing

How do Dobsonians work?

These telescopes have a simple alt-azimuth mount that allows the scope to move in two directions. Alt azimuth is short for altitude-azimuth, which are the two directions in which the mount moves – up and down and side to side (parallel with the horizon). This is an intuitive way of moving the scope while looking through the eyepiece.

The optical tube on these telescope sits in place by friction, making them unique in that respect and non-problematic in starting and stopping the movement of the tube. 

Finally, it is a reflecting telescope, and so it uses mirrors rather than lenses to capture and reflect light to produce an image.

Dobsonian telescope advantages and disadvantages – Quick View

What’s good about a Dobsonian

With a Dobsonian, you get to learn about planets, stars, star clusters, nebulae, deep sky objects (e.g. galaxies), and other celestial objects because of several advantages in using this telescope…

  • Simple to use
  • Price – Far cheaper than another of the same size
  • No need to spend time on polar alignment
  • Great for beginners and all ages
  • Stable – vs tripods that tend to shake when touched

But they do have downsides…

  • Need collimation
  • Aren’t lightweight
  • Not useful for astrophotography
  • Don’t come computerized as in GoTos
  • Not very compact unless you opt for collapsable models

We look at these pluses and minuses in more detail below …

Advantages of Dobsonians

Price: The main advantage and reason most beginners opt for a Dobsonian is the price.

The bigger the aperture, the more it gathers light, right? The more light-gathering ability the more you will be able to observe the fainter details. You can buy a good-sized aperture in a Dobsonian for less than you would any other telescope type.

This is what is meant by Dobsonians giving you “the best bang for the buck”.

Simple fabrication: The second main advantage is the simple construction. All ages and experience levels can enjoy the use of this telescope for this reason, which not only makes it more affordable but also means it has simple controls and a simple mount of alt-azimuth movement.

No polar alignment needed: We cover this in our article explaining the different telescope mounts. It means having to set the latitude of the mount to your current latitude and then making it so the azimuth axis points to the celestial pole, which, if you are in the northern hemisphere, is the star Polaris.

Stable solid mount: The rocker style alt az mount is a solid stable mount that is simple in design so you can use it with confidence without concern of breaking cogs or other finer parts.

Why are Dobsonians cheaper?

Why Dobsonians are more economical is that Dobsonians have a simple design, amounting to a set of optics and a simple mount. This makes them far cheaper than other types of telescopes with the same aperture size.

To further understand this…Mirrors cost less than lenses, which are the optics used in refractors and Schmidt-Cassegrain telescopes, and so the Dobsonians can be made more cheaply than these types of telescopes.

Downsides of Dobsonians

From time to time, Dobsonians require collimation, which is the process of aligning the mirrors so that they work together to deliver well-focused light to your eyepiece.

You can get collimating tools such as a laser collimator or a collimating eyepiece.

It may seem daunting, but once you get the hang of it, collimating your telescope is not that difficult.

See also: How to collimate a Dobsonian

Dobsonians aren’t lightweight (but are transportable). You might take two trips from your vehicle to set it up in place and will need to consider where you intend to store it.

Because a Dobsonian is not computerized (a GoTo), you will need to figure out where to point it to see the object you’re interested in seeing in the sky. Finding the moon is not so much an issue, or the planets usually. But locating those not so obvious objects will require maps and some learning of the night sky. Check out our tips on using sky maps/star charts for beginners.

Dobsonians are not useful for taking photos of the night sky objects. But the positive of this is that (providing you’re not wanting to take photos) with a Dobsonian…there’s no need to spend all that time having to align the mount with the celestial north or south pole (depending on which part of the world you are observing from).

Are Dobsonians good for astrophotography?

The answer is no, Dobsonians are not recommended for astrophotography because the alt-azimuth type of mount they typically have means you can’t track the object you’re wishing to shoot as it moves in the sky with the rotation of the Earth.

If you are into astrophotography, this is a disadvantage with these types of mounts. They do not follow the celestial object in the sky as the Earth rotates and the alt-azimuth mount requires manual adjustment with the two axes requiring different rates of rotation.

What is the difference between a Dobsonian and a Newtonian telescope?

Let’s start with the similarities between these two types.

First, they are both reflector telescopes. That is, they have mirrors, not lenses. They have a primary parabolic mirror and a flat secondary mirror in an open-ended tube with a focuser for an eyepiece on the side.

Next, the telescope tube of a Dobsonian is like all Newtonian reflectors.

Plus the optical assembly of both is much the same, where light enters the tube and is picked up by the primary mirror (objective lens), which reflects it on so that the light is concentrated onto the smaller secondary mirror (which is flat) and then finally into the eyepiece.

choosing the best Dobsonian telescope
What a Dobsonian would look like mounted similar to a EQ Newtonian telescope

So, what is the difference between a Newtonian telescope and a Dobsonian? The mount is the main difference. The mounting of a Dobsonian looks like that of a cannon whereas the Newtonian telescope is mounted on a tripod. By Newtonian, we are referring to those with equatorial mounts.

Dobsonian vs Newtonian mount

The Dobsonian mount is very basic and generally made of timber. John Dobson designed it this way to “bring large aperture views to the masses”.

It is a rocker box alt-azimuth type, which allows manual motion in the up/down (Altitude) or east/west (Azimuth) axes. This compares to the equatorial mount of the other, Newtonians.

Source: Starry Hill Observatory & Planetarium

The alt-azimuth is a type of mount also seen in some GoTo systems people use to track planets, only with a motor and computer.

A look at the size and set up of an 8 inch Dobsonian

What is the best Dobsonian for beginners?

Amateur astronomers rate the likes of the Skywatcher 6-inch as a good starting point for beginner astronomers wanting ‘the best bang for the buck’. Other brands include Saxon, Meade, and Orion.

It’s an economical buy. And, a 6-inch aperture in a Dobsonian means you should get useful views of the moon and planets. A focal length of 1200mm and aperture of 6″ are good for planet viewing.

Look for one with a focuser made of metal rather than plastic and including wide-angle eyepieces for eye relief are good options.

The 6 inch gathers a fair amount of light, and so you’d benefit from getting a moon filter. Also, consider a Barlow lens or an extra eyepiece for more details of planets; just make sure your magnifications work out to be within the maximum magnification limits of the telescope. (I include a quick reference for calculating magnifications with eyepieces in my article on extra eyepieces.)

For greater comfort, a right angle finderscope is another option to consider adding when buying your Dobsonian. Or, another option is a Telrad device. This is a finderscope that projects a bulls-eye pattern onto the sky.

The benefit of using a Telrad is that you’re not having to awkwardly place your eye up close to the finder as the bulls-eye pattern is visible from distances up to a foot or so behind the device.

I’ve recommended the 6″ here for beginners because the 8 inch and 10 inch ones are heavier and take a bit to move and store.

Interested in one of the best Dobsonian brands…Check out the price of the Orion Dobsonian 6-inch at Amazon — See details.

They aren’t that expensive.

In summary

Dobsonians are recommended for beginner astronomers but are also valued by many advanced amateur astronomers. They are far cheaper and easier to use than other types (for the same size optics!) and have a simple stable mount. The downside is that they are not so compact, although you can buy ones with a collapsing tube.

However, if you are wanting to do astrophotography, a Dobsonian is not the answer.

Info resources

NASA Nightsky on choosing a first telescope | Springer Link: John Dobson and His Revolution | Virginia Tech, Dept of Physics: Thinking of Buying a Telescope

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