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Dobsonian vs Reflector [Difference Between the Telescopes]

If you’re looking to get into Astronomy, then there is quite a lot to take in, especially all of the different names and acronyms. When it comes to choosing a Telescope – there’s actually quite a few different styles and types to consider. This is why it is so crucial to conduct some research ahead of time and ensure you know what you need to get to observe what you want. Two of the most popular types of telescopes are the Dobsonian and Reflector. So what is the difference between a Dobsonian and a Reflector? Theoretically, a Dobsonian is a reflector. The only true difference is that just uses a different mount to your average Newtonian reflector. The Dobsonian typically utilizes an Alt Altazimuth mount, whereas general Reflectors make use of an Equatorial Mount. Despite the differences in the mounts, the optics and way they are designed are the exact same when you compare a Dobsonian to a Reflecting telescope. That’s the very basic overview of the difference and hopefully it will have helped you understand the major distinctions between a Dobsonian and a Reflector. However, if you want to learn more about a Dobsonian and why it has become so popular of late, then stick around as I will now discuss this telescope type in greater detail.

Dobsonian vs Reflector

The Dobsonian telescope is only a fairly recent innovation. It is the result of young astronomer John Dobson who devised the telescope in the 1960s. Dobson claimed that he he hadn’t really changed the landscape of telescopes with the Dobsonian, but his modest approach doesn’t reflect the true reality of what he was able to do for the field of Astronomy. The legacy of his revolutionary work is that he has enabled telescopes to be introduced and widely used by astronomy beginners. Buy why is this? The Dobsonian telescope is usually cheaper and much easier to use than other varieties and styles of telescopes available on the market (primarily over Refractors and Cassegrains). Here are the elements of the Dobsonian which have made them to be manufactured considerably cheaper and that enable us to get them for a far more respectable price:

Alt-Azimuth Mount

The Alt-Azimuth mount is the standout and most obvious sign a telescope is a Dobsonian. Every Dobsonian will have an Alt-Azimuth (Altaz) Mount. Now, while this sound rather technical its actually quite simple. An Alt-Azimuth Mount is a simple two-axis mount that supports and rotates the telescope about two perpendicular axes – one vertical and the other horizontal. The Alt-Azimuth mount is considerably easier to use and is therefore an excellent choice for beginners and amateur astronomers. The use of an Alt-Azimuth on a Dobsonian, differs to the commonly used Equatorial Mount used on other Newtonian Reflector Telescopes (some use a variant called a German Equatorial Mount or GEM).


Another important change from Dobson was to replace the expensive fiberglass tubes and swap them out to other material that is more cost effective. These tubes are equally as strong and do not effective performance, but enable the price of the telescope to be reduced dramatically.


In regards to the optics, Dobson also included thinner mirrors on the Dobsonian. This makes them a lot cheaper to manufacturer than Pyrex mirrors (used by other telescopes). The result is that this saving is passed onto us, and we can get our Dobsonian a lot cheaper. Today, the main way we understand a Dobsonian from another type of telescope is primarily the mount (which is far easier to use). To use the Alt-Azimuth, all you need to do is move it up and down and left and right compared its on a two-axis system. Regarding its performance and the optics. As the Dobsonian is technically still a Reflector, it has all of the same mechanisms and components of all other reflectors. So the performance is not any inferior. So if you’re considering to get a new telescope then a good place to start your research will be comparing the difference between reflectors and refractors and then other Catadioptric telescopes.

Reflector Telescopes

Reflector telescopes get their name due to the way the way the optics work within them. They were designed by Isaac Newton which is why you may see the original designs marketed as Newtonian’s. For the most part, the main distinction between a Reflector and a Refractor is that Reflector use mirrors and Refractors use lenses. For this reason, Refractors are typically more costly which accounts for the growing ownership of Reflecting telescopes over the years. This is certainly true in the amateur astronomy market, who are more careful in their investment not knowing if they will pursue the hobby for any extended period of time. Reflecting Telescopes operate via collecting light on from a larger mirror and ‘reflecting’ it back onto a smaller secondary mirror. It is the secondary mirror that projects the image through your telescope eyepiece so that you can observe objects in the sky. As mentioned, due to the design, a Reflecting telescope will be cheaper than a Refractor. There are several Reflecting telescope types (including the Dobsonian) as this guide has covered which can be primarily identified and classified via its mount. You’ll also find Reflecting variants of the Cassegrain, Gregorian and Nasmyth telescopes but that is a subject for another time. These are not typically popular or widely available so I wouldn’t get too hung up on these variants.


I hope this guide has been able to clarify and outline the major differences between a Dobsonian and Reflecting Telescope and you now know precisely what a Dobsonian is. As mentioned, the major distinctions are the Mount, Tubes, Mirrors and Price. If you’re a beginner and looking to get a telescope then you’ll probably be best off with a Dobsonian due to their ease of use and cost. Ultimately it all depends on what you’re hoping to observe and view. Different telescopes and specifications will provide views of different objects and in different detail. If you’re in the market for a telescope that can see Planets, Galaxies and other Deep Space Objects (DSOs) then I suggest you read my comprehensive guide on the best telescopes currently available. I discuss what all the spec means, what to look for and the pros and cons of each model. I’ve also compared spec side by side and taken into account user experience, reviews and results. When you’re new to astronomy, it can be difficult to identify what you need and to distinguish between different styles, variants, brands and models. Nonetheless, if you do opt for a Dobsonian, or any other type or Reflecting Telescope, you’ll be quickly amazed at how easy they are to use and some of the treasures of the sky that they will reveal. Related Guides: