Dobsonian Telescope Advantages and Disadvantages

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A Dobsonian makes a good beginner telescope according to many amateur astronomers. Why a Dobsonian? There are a few reasons, one being the price. If you’re interested in this cheaper design of a telescope, you should first fully consider the Dobsonian telescope advantages and disadvantages before buying to see if it is right for you. Here’s the info…

Dobsonian telescope advantages and disadvantages

Some best Dobsonian telescope reviews recommend Dobsonians.

Is a Dobsonian telescope good?

Are Dobsonian telescopes good for viewing planets?

A Dobsonian telescope will give you pretty decent views of planetary and lunar details providing you choose one with an aperture of 6 inches or more.

I cover the recommended aperture size in the different telescope types in my article on what to look for when choosing telescopes for planet viewing.

But why get a Dobsonian telescope?

With a Dobsonian, you will be able to quickly set up your telescope and easily point it at the Moon, Mars, or other celestial objects and get decent views on a night that’s perfect for observing.

These have a wide field of view and a simple mount that allows the scope to move in two directions – not difficult!

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

Dobsonian telescope advantages and disadvantages in a nutshell

What’s good about a Dobsonian

  • 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

Some of the downsides to consider…

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

Read on for more details around these advantage and disadvantages regarding a Dobsonian…

Advantages of Dobsonians in more detail

If you’re wanting to view planets, stars, star clusters, nebulae, or galaxies, then you can’t go past a Dobsonian because it takes little time for you to have it outside and set it up to view the night sky objects with ease.

All ages can enjoy the use of this telescope because of the simple controls and movement due to the type of mount of Dobsonians.

But then, the main advantage and a reason you might want to get a Dobsonian telescope is the price.

You can buy a good-sized aperture in a Dobsonian for less than you would any other telescope type. These are far cheaper scopes (for the same size optics!).

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.

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

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 understanding this…Mirrors cost less than lenses, which are the optics used in refractors and 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.

For this, you can get collimating tools, which can include a laser collimator or a collimating eyepiece.

It may seem daunting, but once you get the hang of it, collimating your telescope will be a breeze. I gave a step by step account in my article on collimating a Celestron SCT.

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. You can check out my 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 Dobsonian telescopes good for astrophotography?

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

What is the difference between a Dobsonian and a Newtonian?

Let’s start with what’s the same 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 set on the side.

Next, the optical part of the telescope or OTA (Optical Tube Assembly) in a Dobsonian is like all Newtonian reflectors.

In both, light enters the tube and is picked up by the primary mirror, 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 telescope would look like mounted like a Newtonian

So, what is the difference between a Newtonian and Dobsonian telescope? The mount is the main difference. The mounting of a Dobsonian looks like that of a cannon whereas the Newtonian is mounted on a tripod.

Dobsonian telescope 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.

Check out the diagrams I’ve included in my guide explaining telescope mounts to get a visual of this difference.

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 telescope for beginners?

Amateur astronomers rate the likes of the Skywatcher S11600 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.

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 telescope brands…Check out the price of the Skywatcher Dobsonian 6-inch at Amazon — See details.

Skywatcher Dobsonian telescope 6 inch review

This 6 inch Dobsonian is rated a great telescope, made well, with the focuser made of metal rather than plastic. It has great wide-angle eyepieces for eye relief. Its focal length of 1200mm and aperture of 6″ make it good for planet viewing.

It comes with all the parts and tools to assemble it (assign about half an hour).

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 telescope. 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.

They aren’t that expensive. You’ll find the latest price and reviews at Amazon. Click the image for more details.

In summary

Dobsonians are recommended for beginner astronomers, but are also valued by many amateur astronomers. They are far cheaper and easier to use than other types 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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