Dobsonian vs Newtonian [Why and How Are They Different]

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When it comes to selecting your new telescope, you’ll first be faced with all the different types. There’s a lot to consider and chances are you will have come across Dobsonian’s and Newtonian’s during your research. But why and how are they different? What is better and what should you choose?

The truth is that with all the different names, terminology, acronyms and brands, it can all be confusing and overwhelming when you’re first starting out.

Dobsonian and Newtonian Telescopes are some of the most popular and recommended types to get, and there appears to be a school of thought that think they are completely different. This is in fact, not the case.

A Dobsonian can be a Newtonian and vice versa – they are not always mutually exclusive. Here’s why. The term Newtonian is referring to the optics of the telescope. The term Dobsonian is referencing specific features e.g. an Alt-Azimuth Mount, Thin Mirrors etc of a Newtonian Telescope. So when you come to think of it you could have a standard Newtonian Telescope or a Dobsonian Newtonian telescope. You see how it works?

Understanding the technical terms can be tough – I’ve been there myself. This is why its best to understand the nuances before you decide to invest in a telescope. If not, you risk purchasing a telescope that is not going to be suitable for your needs and preferences.

To help you, I’ve pulled together a collection of features that you can use to distinguish between the two telescopes.

Dobsonian vs Newtonian

Hopefully by now you have a rough understanding of the nuances between them. They’re very closely related and in a lot of circumstances they are one of the same thing.

However, this is not always the case so let’s delve a bit deeper to help you distinguish them more readily.

What Is a Newtonian Telescope?

The Newtonian is a specific design of telescope that was invented in 1688 by Isaac Newton. Specifically, a Newtonian is a Reflecting telescope – optics that ‘reflect light’ as the name suggests.

Here’s a summary of how a Reflecting Telescope actually works:

The design is focused around two mirrors, a primary and smaller mirror. The primary mirror collects light. It then rebounds that light onto the smaller secondary mirror which focuses the light to produce an image for you to observe through the eyepiece. The use of Mirrors enables the light to be reflected and ‘bounced’, opposed to simply passing through which would be the case if a transparent component (like glass) was used.

Due to the structure and design, a Newtonian telescope is considerable easier to build than other reflecting telescope variants, like a Cassegrain. This means that Newtonian’s are typically cheaper and more cost effective than the a Cassegrain of similar specification.

What Is a Dobsonian Telescope?

It is clear to note that a Dobsonian cannot be classified by its optics, rather the type of mount that it utilizes. This is actually a common and misunderstood distinction.

Another frequent curiosity is whether a Dobsonion always is designed with Newtonian Telescope Optics. The truth is that this is the case the majority of the time. This all due to the placement of the eyepiece which is actually ideal for a Dobsonian.

Now, the Dobsonian was designed in the 1960’s as a way to get beginners and amateurs into astronomy. Itis actually a pretty interesting story how the inventor Jon Dobson made astronomy viable for the masses through his design starting with his astronomy club in the United States.

The major reason for its ascendancy and rise to become one of the most common types of telescopes used is due to its performance coupled with its availability and affordability. It’s an ideal entry level telescope so if you are new to astronomy it is probably the best way to start.

Dobsonian telescopes are typically used to obverse Deep Sky Objects (DSOs), Galaxies along with the planets of the Solar System. As it utilizes Newtonian reflecting optics, it can collect maximum light which is critical for any celestial observation (the more light the better). As more light can be collected, so is the ability for us to observe more distant, fainter objects that would otherwise be covered in darkness. Taking this a step further, being in low light conditions that also encompass limited pollution will give you the best results and observations.

One of the other major benefits of a Dobsonian telescope is that due to their short focal length, in terms of size and weight they relatively compact. This makes them easy to transport and take with you on the go.

Key Differences of a Dobsonian 

Now in most cases a Dobsonian will be a Newtonian (from an optical perspective). However, there are some certain components that differ on a Dobsonian that do not appear on a Newtonian. They are as follows:

Alt-Azimuth Mount – This is the prime distinction of a Dobsonian . An Alt-Azimuth mount is surprisingly a really straightforward design (despite its complicated name!) Chances are, you’ve seen or used one on a telescope before because this is the most common type of mount (outside of the other common Equatorial).

An Alt-Azimuth mount is one of the easiest to use. Its basically a  simple two-axis mount that supports and rotates a telescope about two perpendicular axes – one vertical and the other horizontal. Rotation along the vertical axis changes the azimuth (compass bearing) and the pointing direction of the telescope.

Tubes – For a long time and on a lot of telescopes, aluminium and fiberglass was the material that was used to construct the Tubes. This was on one Dobson’s changes – he realized the expense of these elements and swapped them out for a form of solidified construction paper. Believe it or not, this has actually made the Dobsonian more durable, and also makes it lighter and lowers the risk of any potential accidental damage. One thing to note is that the tubes used on Dobsonian’s are typically double the length of regular Newtonian’s, this is to house the flat secondary mirror compared to a curved equivalent on a Newtonian.

Mirrors – The final major difference is the types of mirror that are built into the Dobsonian telescope. They are actually much thinner and cheaper in the Dobsonian which makes them more affordable without compromising power and performance.

As you can see, the major differences are in the material used for the components. More expensive components have simply been swapped out for cheaper alternatives. This has enabled Dobsonian’s to become much much more affordable whilst retaining the same quality optics of more expensive and traditional Newtonian telescopes.

Final Words

For the most part, when it comes to performance there’s not going to be a lot of difference between a Dobsonian and a Newtonian. If you are new to astronomy, a Dobsonian is going to offer you a high performing telescope at a much cheaper price point. Plus, it will be more portable.

When it comes to choosing a Dobsonian telescope, you’ll notice that there are a lot of different options and brands available. Selecting one is going to depend on your preferences, needs and of course budget.

The Dobsonian StarBlast Range from Orion, which are all available on Amazon at great and often discounted prices, have some of the best reviews and user experiences. I suggest if you want a Dobsonian that you take a look. The StarBlast 6 is an excellent place to start and a great model to own.

I hope that this article has provided you with an overview of these two different types of telescopes.  If you have any further questions please do not hesitate to drop them in the comments section below. I will do my utmost to help!

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