You came across refracting and reflecting telescopes, but you also found that there is such a thing as a Dobsonian telescope.
What are Dobsonian telescopes and how are they different?
Are Dobsonians any good?
Are Dobsonians affordable?
I hear you – your mind is racing with questions, and we’ll get to the answers together.
Let’s learn a thing or two about them and why you should consider buying one if your sights are set on the deep-skies beyond.
Best Dobsonian Telescope In 2020
What is a Dobsonian telescope?
In short, it’s acceptable to say it’s a Newtonian reflector OTA with an alt-azimuth mount made with plywood and a large base to support the telescope system. Dobsonians are often called “Dobs” for short, and they’re also nicknamed “light buckets.”
Who made the Dobsonian?
In the ‘60s, John Dobson was recognized for creating this telescope setup that provided a large aperture and portability at a low price point.
Who is the Dobsonian for?
The Dob is a favorite type of telescope for astronomers of all skill levels. They’re especially attractive to amateurs and beginners because they offer ease of use, a huge aperture, and the best bang for the buck when you’re just starting out.
What is a Dobsonian good for seeing?
Thanks to the huge apertures available with the Dobsonian, they provide excellent seeing quality for bright and faint DSOs.
There’s no denying that Dobsonians are very attractive telescopes to own and you may end up owning more than one in your lifetime. Here are a few that you must consider if you’re thinking about buying a Dob for the first time or if you’re adding to your collection.
Best Dobsonian Telescope Reviews
1. SkyWatcher FlexTube 250P SynScan
Since Dobs are usually associated with simplicity, I had to throw in a high-end and more complicated model, the FlexTube 250P SynScan.
Pros & Cons
✔️ 10” aperture
✔️ Parabolic mirror
This model is part of the FlexTube series that indicates it’s a collapsible Dobsonian. As a collapsible Dob, it has both benefits and drawbacks that only you can determine if it’s worth the buy, and yes, it’s more expensive thanks to its many perks.
The OTA has a 10” aperture with a fast optical speed and long focal ratio – good for imaging with. You can count on excellent optical quality here. The collapsible feature consists of rods that retract and extend in place, so you don’t have to deal with actually removing any rods and parts. This is a good storage and transportation feature.
The SynScan feature indicates that this model has GoTo. It comes with the SynScan hand controller, the mount has a dual-axis motor drive, and built-in WiFi. With this feature, you’ll have some imaging benefits in the palm of your hand. The mount still only has AZ movement. Unless you’re willing to dabble with de-rotation imaging software, short exposures it is.
The FlexTube SynScan Dobsonian has more features than your typical Dob. Some like the simplicity of manual mounts for outstanding visual use, and others want a little more out of their setup to dabble in imaging. If that’s you, this is the scope you want to “dabble” with.
2. SkyWatcher Traditional 8” Dobsonian
This is a perfect example of 8” of excellent seeing at an incredibly good price point. This model proves that you can have stellar Newtonian performance for the least amount of money.
Pros & Cons
✔️ 8” aperture
✔️ Parabolic mirror
✔️ Wide field of view
❌ Lacks bells and whistles
The best thing about the 8” Dob is its simplicity. Its main drawback? Its simplicity. With the huge seeing and wow-factor through the scope, it’s unfortunate that you can’t share it with images. Since it’s not an imaging telescope and it doesn’t claim to be anything more than what it is – an exceptional visual telescope, there’s nothing to be deceived about from the start since you know what you’re getting.
The OTA has a good 8” aperture with a fast focal ratio. Needless to say, this is going to be good for deep-sky views. With a parabolic mirror, you won’t have any spherical aberration issues and there isn’t any coma detracting from the experience like you may have with a much larger, just as fast, model.
In all reality and with a look at the specs, the 8” is just as portable as the 6” model, so you’re not really losing out on any convenience benefits by upgrading to the larger size. There is plenty to see with this Dob, and with 203 mm of aperture, you can take advantage of dark skies to access the thousands of DSOs waiting to be explored.
3. Orion SkyQuest XT8
The SkyQuest XT8 is a Dobsonian that has been around for a long time. To have stayed a popular model over the years, it must be doing something right. Let’s check it out.
Pros & Cons
✔️ 8” aperture
✔️ Parabolic mirror
✔️ Wide fields of view
✔️ Manual model
❌ Small bearings
The SkyQuest XT8 is within the right price range for its specs and performance. It’s a manual 8” Dobsonian with a parabolic primary mirror. The views will be as expected for everything that you expect from an 8” – fantastic.
This is a good starter telescope for a beginner who wants the best value out of their buy. However, you will have to acquire more accessories since it only comes with one low power eyepiece, a 25 mm. So, save some room in the budget for, say, an extra eyepiece and a Barlow lens.
When it comes to the mount, you have a carry handle on the base which is very convenient for travel, and it’s relatively light at 21 lbs (approx.). It also features Orion’s CorrecTension spring system to help out with balance and secure attachment to the base. The bearings are small and may be able to be replaced with larger ones to provide ultra-smooth movement.
Since this is a manual model, it’s easy to use and is great for visual observations. If you want more out of it, you can upgrade it with a clock drive, but there is a SkyQuest GoTo version of this model that may be worth considering instead. All in all, it’s just like its competitors out there and is worthy of consideration.
4. Zhumell Z12 Deluxe
12” of aperture is a whole new ball park of seeing and additional hassles you’ll have to deal with. So, if you’re after the largest aperture you can afford for under $1000, you’ve found the scope where the buck stops.
Pros & Cons
✔️ 12” aperture
✔️ Parabolic mirror
✔️ Bearing upgrades
✔️ Cooling fan
The Z12 is going to be heavy – it’s a huge 12” aperture you’re dealing with. The entire assembly weighs in at 75 lbs and the tube is 58” long. It’s not an easy scope to transport and setup alone, but still, observers have hauled scope systems close to and over 100 lbs before – something to think about in context.
The Z12 with its large 12” will provide exceptional details on faint objects. It’s more suited to DSO observation because of its fast focal ratio of f/5, but you can also see planetary detail a whole lot better thanks to the higher useful magnification.
With such a large size, you may be worried about thermal management. The price is justified not only in aperture size but also because it comes with a parabolic mirror and cooling fan. The cooling fan will help to keep quality visibility during your observation sessions.
Thanks to the sheer size of the Zhumell telescope, the bearings have seen an upgrade with ball bearings in altitude and roller-style in azimuth.
The Zhumell telescope is a buy for a more experienced user looking for the largest aperture for the buck for some great visual benefits.
5. SkyWatcher Traditional 6” Dobsonian
Though not as large as some of the Dobs in this lineup, it’s still a true Dob. The benefits? Cheaper price, increased portability and convenience, and you still get the big aperture.
Pros & Cons
✔️ 6” aperture
✔️ Included extension tubes
❌ Plastic bearings
The plastic bearings probably stuck out like a sore thumb. They’re not the best, and you still have Teflon pads that provide some smooth motion, but it could present some issues down the road. For the amateur who doesn’t know better, they’re pretty happy with mount performance. For the experienced user, you’ll likely want to upgrade these parts when you can.
What about the optics? Excellent as expected. 6” aperture, parabolic mirror, and a 2” focuser with both 1.25” and 2” extension tubes. You can switch out various types of eyepieces for magnification and field of view based on needs since you’re not limited to size.
With a 6” and f/8 speed, you sort of have a general-purpose telescope. You can see double stars, excellent planetary detail, and hundreds of star clusters, galaxies, and nebulae.
The balance between cost and size extends to its portability benefits. The tube is incredibly lightweight, and the base does not exceed 30 lbs. You can pack this baby and haul it across country if that’s where you can get the best views – no issues there.
What to Look for in a Dobsonian Telescope
It can be confusing to understand the different types of telescope optical designs out there. The nice thing about Dobsonians is that they’re simple to understand, use, and design.
Fun fact: Dobs are a fun telescope building project attempted by many amateur astronomers.
If you’re not at that DIY level yet, keep reading to learn more about the Dobsonian light bucket.
How much should you spend on a Dobsonian? How much do they cost?
Dobsonians, like Newtonians on a tripod, offer more value per inch in aperture compared to refractors. So, they’re a lot cheaper than refractors and are therefore easier to afford. Much of this is due to the fact that mirrors are easier and cheaper to manufacture than the glass components needed in a refractor. Additionally, you have a cheap, wooden mounting base that provides simple alt-az movement. The idea behind this is to put as much money and quality into the optics with an uncomplicated mount/base setup.
At the affordable end of the spectrum of a budget of $100 to $300, you can buy a 2.5” to 4.5” Dobsonian that is mainly designed for portability and convenience.
At $400 to $600, 6” to 8” Dobsonians come into the picture and are what I would typically call full-size, floor telescopes. Obviously, the more money you spend, the larger the aperture gets.
At $1000 and above, GoTo, digital setting circles, truss rods, and collapsible features come into play. At this price point, they can be large in aperture or only 8” in size but have extra perks.
In setting a budget, it’s best to buy the largest aperture you can afford. Keep in mind weight specifications and the need to acquire upgraded accessories sooner than later.
There are a lot of attractive telescope features on a Dobsonian. Here’s the good.
- Large apertures
- Large aperture benefits (i.e. see faint objects)
- Best value in aperture per inch versus refractors
- Easy to use
- Simple, easy to use mount
- Beefy, robust mount
- Available at various price points
- Available with additional upgrades/features
Then, there are the limitations of a Dobsonian’s simplicity.
- Not for astrophotography
- Alt-azimuth mount
- No equatorial mount benefits
- Large sizes are heavy and make it difficult for travel
TableTop VS Full-Size Dobsonians
Dobsonians come in different sizes and are usually categorized by two types: tabletop or full-size. They each have their benefits and drawbacks, but it comes down to user preference in which type will be most appropriate for your needs.
In this context, tabletop setups consist of a Newtonian OTA on a Dobsonian-style base at a much smaller scale. These types of Dobsonians are not usually called “Dobsonians” in the true sense of the word. They’re marketed as tabletop telescopes because they’re short in size and are designed to be placed atop a flat and solid surface such as a table.
Tabletop scopes are usually entry-level models at an affordable or beginner price point. The OTAs equipped on such a mount/base will have a smaller aperture than a full-size Dobsonian. They’re lightweight and usually come preassembled from the factory.
Full-size Newtonians on a floor-based mount/base are Dobsonians in the true sense of the word. They have large apertures which means a larger base is required which means a heavier weight. Full-size Dobs have no need to be mounted on a table. They can be placed directly on the ground/floor.
Full-size Dobs may start at $400 and will go up in price based on aperture and additional optical and base features. Larger models will be difficult to transport due to size and weight. You may need an extra hand with you to help with setup and disassembly. Very large Dobs may be less suited to travel but are great options for stationary observation like in a private/backyard dome for example.
Dobsonian Maintenance Considerations
Dobsonians may have a simple and easy to use mount, but since the OTA is a reflector, there are some maintenance issues to consider.
Collimation is required of every good Newtonian telescope. Many cheap telescopes may have a glued primary mirror that is fixed in place and does not allow for collimation. This can be typical of a tabletop telescope, so look for a collimatable cell if you’re considering a tabletop Dob.
However, the larger the size, the more likely the primary mirror is to become misaligned during transportation or rough handling. It’s recommended to collimate a Newtonian before every use, although it may not be necessary if it’s not being moved or disassembled between use.
Collimation does require a learning process for the beginner but can be easily done with a collimation cap that is sometimes included in a telescope package.
Spherical VS Parabolic Mirrors
Spherical and parabolic refers to the shape/curved surface of the mirrors in a Newtonian. Spherical mirrors are seen in inexpensive and expensive Dobs. The difference in whether it will suffice can easily be determined by looking at the focal ratio. If the focal ratio is f/5 or lower (has a fast optical speed), a parabolic mirror would be a necessity. If the focal ratio is higher, and therefore slower, a spherical mirror is adequate.
What’s the difference?
A spherical mirror in a fast telescope means that light rays are unable to come to the same focal point after bouncing off the spherical surface because of the short focal length. This produces an optical aberration known as spherical aberration. It looks like things are blurry and sharpness cannot be achieved even with focusing.
A parabolic mirror allows light rays to come to the same focal point after bouncing off the parabolic surface. This helps to improve optical quality in fast Newtonians.
Obstruction consists of the secondary mirror in a Newtonian interfering with light-gathering and contrast benefits of this type of telescope. All Newtonians have obstruction, but the size of the secondary mirror will be different among various models. This type of obstruction is often referred to secondary mirror obstruction.
There are formulas for determining the size of obstruction by millimeters and percentage. The rule of thumb is to take the secondary mirror size and subtract it from the primary mirror size. For example, a 203 mm (8”) Newtonian with a 50 mm (2” approx.) secondary mirror would result in a 2” obstruction. This essentially means that an 8” Newtonian will behave like a 6” Newtonian.
Many astrophotography Newtonians have obstruction around 40%. If obstruction is at 20% or lower, the effects become less noticeable.
What is the effect of a warm telescope mirror on optical quality? Blur. The larger the primary mirror, the longer it will take for it to cool down. At medium to high magnification, a warm mirror will negatively affect your visibility and you may mistakenly misdiagnose it as bad atmospheric conditions.
Unlike collimation and obstruction that are inherent “flaws” (if you will) of the Newtonian design, thermal issues are solvable. If you want a large Dob, look for one with a built-in fan or a design that allows you to install a fan.
Who Makes the Best Dobsonian Telescope?
Zhumell is not an authoritative brand, but they provide some excellent Dobsonians for the money. They are especially recommended for beginners that are looking for a Dob as a first-time telescope.
Well-known brands that consistently produce Dobsonian telescopes include Celestron, Orion, and SkyWatcher.
Are Dobsonian Telescopes Good?
Dobsonian telescopes made with good quality are excellent telescopes to own and use. They come in different sizes and with optional, additional features to enhance both optical and mount performance.
However, even the simplest Dobs are worthy of consideration as they provide value due to their larger aperture per inch versus refractors. The compromise is the simple mount. So, Dobs make excellent visual telescopes for all types of observers. They do require the maintenance of a Newtonian, so that may affect your decision.
What can you see with a Dobsonian Telescope?
Dobsonians are champs for seeing faint objects like DSOs. Of course, they can see the brightest DSOs just like a small-sized telescope.
What you can see will be determined by the specs. What is the aperture? That will determine light-gathering ability and highest useful magnification you can use. What is the focal ratio? That will determine how much of a field of view you have to work with and typically what kind of objects your Dob may be best for seeing. Look to the optical quality and specs to determine what you can see and how you will see them.
A very general guideline of expectations per aperture would be:
- Up to 3”: Lunar detail, planets, and dozens of DSOs
- 5” to 8” (200 mm): More lunar detail, planets, some planetary features, and hundreds of DSOs
- 8” (203 mm) to 14”: Exceptional lunar detail, planets, exceptional detail on planets, and thousands of DSO.
Can I do Astrophotography with a Dobsonian?
Dobsonians are not made for astrophotography. One obvious reason is due to the limitations of the box-rocker-style alt-azimuth mount. Another reason is there is often not enough in-travel focus to allow DSLR cameras to come to focus for imaging.
However, it’s not the end-all, be-all. Dobsonians can be equipped with GoTo EQ mounts to allow for clock-drive tracking. They can also be modified by an experienced user with use of appropriate accessories to allow for achieving focus.
For visual use, you can’t go wrong with a Dobsonian. You get good value for the money, a huge aperture, and a mount that’s simple enough to use.
There are some things to look for if you want to get the best performance that best suits your astronomy goals, but it’s not too difficult to understand. That’s the beauty of a Dobsonian – they’re easy to use, you get incredible visibility, and they’re easy to justify buying.