If you’re just getting interested in astronomy, then all of the different terms that they use can be extremely confusing. So, it’s important that you do some research online prior to purchasing a telescope. You need to know what type of telescope you’re getting. Two of the most popular terms that you’re going to hear when people are referring to their telescopes are Dobsonian and Reflector.
Technically, a Dobsonian is a reflector itself, but it just has a different mount than your typical Newtonian reflector. Whilst a Dobsonian uses a Alt/az (altazimuth) mount, normal reflectors will use an equatorial mount. So whilst the mounts are different, the optics are the same as a Dobsonian is a reflecting telescope.
Hopefully, that’s cleared things up a little bit in terms of what exactly a reflecting telescope is and the difference between that and a Dobsonian. But, if you’re interested there are things that make a Dobsonian what it is, and why it’s become the telescope of choice in recent years.
Dobsonian vs Reflector
The Dobsonian is one of the younger telescopes, coming to the forefront in the mid 60s by amateur astronomer John Dobson. Ever the humble man, Dobson himself often said that he didn’t ‘invent’ much with the Dobsonian, yet he was the first to put all the pieces of a Dobsonian together. In reality, Dobson is underestimating his contribution to astronomy, as his telescope helped to introduce astronomy to more amateurs.
This is because the Dobsonian is generally a cheaper, easier to use version of the other types of telescopes out there, especially refractors and Cassegrains. There are a few things that Dobson decided to do to make the Dobsonian more cost effective to the every day person.
- Altazimuth mount – This is the telltale sign of a Dobsonian telescope – they all have Altazimuth, or Altaz, mounts. This is opposed to the typical equatorial mounts that are used with other telescopes (most other reflectors use GEMs, or German Equatorial Mounts). The mount is much easier to use for amateur astronomers. Nowadays, this is the main difference between Dobsonians and other Newtonian reflectors.
- Tubes – Dobson decided to use different tubes as opposed to the expensive fiberglass tubes that were being used. Instead, he used the same tubes that are used to hold cement, which were strong enough for a telescope – and a lot less expensive.
- Mirrors – Dobson also introduced thinner mirrors to his telescopes, which made them much cheaper as opposed to the thick Pyrex mirrors that others used.
Nowadays, we really just refer to Dobsonians being called this because of their mount, which is really easy to use. As it works on a two axis system, you can move it up and down and left and right relatively easily.
From an optical perspective, the Dobsonian is still a reflecting telescope which means it follows all the same principals as other reflectors – you should find out the difference between reflectors, refractors and catadioptric telescopes before you decide on what telescope to get.
Reflectors themselves are defined because of the way that they work optimally. Generally, the easy way to differentiate between a reflector and a refractor is that whilst reflectors used mirrors, refractors used lenses. This of course makes refractors more expensive, and is why reflecting telescopes have seen an increase in popularity in recent years. This is especially true amongst amateur astronomers, who don’t want to fork out a ton of cash when they’re unsure on the hobby itself.
Essentially, a reflecting telescope works by collecting light and ‘reflecting’ the light back from a large, primary mirror onto a smaller, secondary mirror. The secondary mirror then projects an image through the eyepiece and voila – an easy to use telescope. As I’ve said, the reflecting telescope is a cheaper alternative to a refracting telescope, and it was designed by Issac Newton – hence why the original reflector is known as a Newtonian.
There are other reflecting telescope variations now like the Dobsonian, which we’ve clarified refers to the mount primarily. There’s also reflecting variations of the Cassegrain (there’s also catadioptric variations too), as well as Gregorian telescopes and Nasmyth telescopes, which are some of the less common variations of reflecting telescope.
Hopefully, this has helped you to clarify the differences between and reflector and what exactly a Dobsonian telescope is. If you’re looking for a cheaper priced telescope, then it’s probably a wise idea to look at getting yourself a Dobsonian as they provide excellent value for money.
Depending on what you’re looking for, different telescopes can offer you different things. If you’re looking for something that can see DSO’s (Deep Sky Objects) then it’s a good idea to find an easy to use telescope that’s capable of doing this – generally, reflectors are better for faint DSO’s like galaxies, whilst refractors are a better choice for things like planets.
When you’re starting off, it can be overwhelming discovered all of the different terms that are used within the astronomy field. But, after you get started you’ll soon realise what you were missing! A reflecting telescope, whether a Dobsonian or not, is always going to be a good choice.