Dobsonian vs Newtonian – Is There A Difference?

Astronomy is a beautiful profession and gazing at the endless skies with countless cosmic gems therein enriches both the spirit and mind. However, just like with every other calling, it requires patience and diligence to get through the first baby steps.

Obviously, the very start line of every astronomer (or astrophotographer) is finding the right telescope and all the gear that follows suit. Today we’re going to touch on but a speck of the main telescope categories – Dobsonian and Newtonian. 

Is there any difference between a Dobsonian and Newtonian?

From a purely constructive point of view, there are several differences between Dobsonian and Newtonian telescopes; first, and most obvious being lexical in nature, and the second referring to physical differences in their design.

Apart from that, there are also numerous similarities between these two telescope types. As a matter of fact, a telescope can possess traits of both types at the same time. Newtonian telescopes are ‘reflectors’ basically while Dobsonian telescopes feature slight modifications on the mount. 

Since this vague description of the two doesn’t really answer the question of ‘is there a difference’ between them, we need to delve a bit deeper into detail to get a conclusive, definitive answer. Let’s begin with their actual definitions.

Newtonian Telescope 

Newtonian telescope was named after the famous inventor called Isaac Newton. Apart from being singlehandedly responsible for a massive scientific quantum leap after defining and gaining understanding of what gravity is, he invented a contraption that shortly after became the first reflector, or better said, a ‘reflecting telescope’.

Of course, reflectors weren’t the ‘first and original’ telescopes – refracting telescopes predate them by a couple of decades (six, to be more precise), so it’s highly possible that Newton borrowed from their design. It would be more than fair to say that he actually even ‘improved’ it. 

Differences between Newtonian and Reflecting telescopes 

Since we’ve already established that a single telescope can have traits, specs, and characteristics of multiple telescope types, it’s also clear that a telescope can be a ‘Newtonian Reflecting Telescope’. However, these two categories are not one and the same. 

Basically, Newton ‘modified’ one of the earlier versions of the reflecting telescope and instead of a lens he added a mirror for the collection of light. Of course, the main feature of later reflectors, as well as one of the main differences between reflectors and refractors is whether the telescope in question uses a lens or a mirror. 

Most Newtonian telescopes use special ‘parabolic’ mirrors. Given the fact that certain reflectors use them too, we can say that such models are ‘Newtonian Reflecting’ telescopes. 

Dobsonian Telescope

At the opposite end of the spectrum lies the Dobsonian Telescope. In essence, the design of the Dobsonian Telescope, or rather its invention was a long process. Most sources state that it was invented and designed by John Dobson, after which it was named. Originally, Dobson called his invention the ‘Sidewalk Telescope’, as it was basically a tool aiding his sidewalk astronomy calling.

This type of telescope sits on alt-azimuth mount and sports a simple, straightforward mechanical design. These telescopes are fairly easy to craft due to the availability of the components needed for the manufacturing process, and so they’re often much cheaper than Newtonian models. 

The first and main difference between Dobsonian and Newtonian telescopes is the alt-azimuth mount, obviously, but there are other notable differences, such as the portability of Dobsonian models opposed to ‘static’ Newtonian ones; significant differences in the levels of chromatic aberration, and such. 

Additionally, Dobsonian telescopes are best suited for amateur astrophotography and astrology whereas Newtonian models are equally suited for professional use as well. Dobson actually built the telescope with amateurs and those looking for affordable telescopes in mind.

Characteristics of Dobsonian telescopes

While it’s somewhat hard to differentiate reflector telescopes from Newtonian ones, most people can easily recognize a Dobsonian telescope by simply looking at its specs and features. Dobsonian telescope’s main characteristics are:

  1. An alt-azimuth mount; regardless of size, it’s always an equatorial mount with its clock-drive pulled out. Equatorial mounts are typically huge in size and relatively expensive, so alt-azimuth mount is a perfect substitute that doesn’t compromise functionality for the sake of extra portability and convenience. 
  2. Large diameter of the objective; even though Newtonian telescopes also sport a large-diameter objective, Dobsonian models are often supplied with sizable ones that aren’t as heavy. 
  3. Bulky, relatively unwieldy design; Dobsonian telescopes are pretty compact due to the simple alt-azimuth mount they’re placed on, but they are also typically quite big and heavy.

Why do professionals prefer Newtonian telescopes over Dobsonian models?

Or, in another words, what is the reason why beginners tend to start with Dobsonian telescopes? Simply put, they’re significantly cheaper, and astronomy and astrophotography are typically followed with an abundance of expenses. 

On another hand, Dobsonian telescopes are more compact, which allows you to be a bit freer with experimenting during field astrophotography, for example. Professionals usually have their own favorite ‘spot’ or an observatory they use or rent; if you have the space to spare (and know exactly what you want to look for), Newtonian telescopes can help you out just as much.

Conclusion

Yes, differences between these two telescope types exist. They’re designed differently, they were invented at different times, and they offer different kinds of benefits while also coming with a different set of disadvantages. However, now that you know what sets them apart, it should be easier for you to pick which type caters to your needs more. 

About Derek

Hey! I'm Derek, I've been interested in astronomy since.. well, forever! I'm an engineer by trade, but I've been playing around with telescopes for many years. I hope to impart some of the knowledge I've learned over the years onto you!

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