Over the last 12 years my role as planetarium director, astronomy educator, advisor to my high school astronomy club, and president of a local public astronomy club, has made me the target of a very common question.
"Which telescope should I buy?"
If you are looking for a visual telescope to use with your eyes rather than to do astrophotography, this blog post if for you.
Benefits of the Dobsonian Telescope
I am a big proponent of the dobsonian style of telescope for the beginner in visual astronomy. I would say that 90-95% of beginners who are interested in visual astronomy benefit most from starting on this type of telescope. Dobsonians are a telescope design that provides significantly large optics and usability for the beginner, at a very reasonable price tag. They are bar-none the best "bang for your buck" of any telescope design out there. In addition to these large optics, the base of the dobsonian is surprisingly simple in both design and usability given they do not require a tripod or control knobs. The lack of the tripod makes for a very strong and stable base. Be sure to place it on relatively level ground, and then simply push the telescope to where you want to view the sky.
It's All About The Foundation
One of the big failures of similarly priced telescopes is that although they may have an otherwise good optical design, their failure lies in their foundation. The fact is that for a similar price, telescopes mounted on tripods tend to be very shaky, are poorly designed mechanically, and often break. Dobsonians, on the other hand are literally made of plywood/fiberboard bases and are extremely rugged. If they do break (which would be very challenging to do) you could legitimately make your own base with some very basic woodworking tools and supplies from your local home supply store.
"I am a big proponent of the dobsonian style of telescope for the beginner in visual astronomy."
Which Telescope Do I Recommend?
The telescope I find myself referring most often now for visual use is the Orion SkyQuest XT8 plus.
Throughout the blog, I will be recommending Orion products simply because I have used them personally and have had a lot of successful nights with these products. Dobsonians are produced by various other manufacturers, but I have not personally tested them and as a result do not feel comfortable recommending them to you.
The XT8 Plus provides some very good optics, and at 8" is capable of making out some deep sky objects from your backyard. The "plus" also means an upgraded dual speed crayford focuser (the part that allows you to make the image sharper) with an 11:1 fine-focus to get pinpoint sharpness as well as upgraded eyepieces and barlow lenses that come as part of the kit. The XT8 Plus also has a friction-mount tensioner that allows you to adjust the movement of the telescope to account for the added weight of various finderscopes and eyepieces.
I have used the less expensive "Classic" version of this telescope and although I enjoy the views, there is much to be desired with the focuser as well as the hold-down springs that attach the telescope to the base. I cannot stress the importance of these upgrades when making your purchase. It is one of the most frustrating things to spend a few hundred dollars only to find out that you should have made a slight upgrade to get to that next level of "frustration free astronomy" that so many of us struggle through.
"It is one of the most frustrating things to spend a few hundred dollars only to find out that you should have made a slight upgrade to get to that next level of "frustration free astronomy" that so many of us struggle through."
I considered recommending a less expensive suggestion in the Orion SkyQuest XT6 Plus, but I personally do not feel that 6" reflectors (given the price difference being rather small to upgrade to the 8") is really worth the significant decrease in capability offered in the 8" version. Additionally, the size difference in the 6" is not sufficiently small enough to provide any real level of added "portability" to speak of.
Can a Dobsonian Telescope be used for Astrophotography?
Before I go any further, I want to be very clear here, that dobsonian telescopes are meant for visual astronomy and should NOT be considered a good option if you plan to do serious astrophotography. You can certainly do some video astronomy, take images of bright objects like the moon, planets, and even the international space space.
I have spent MANY nights using my cell phone with a small cell-phone mount like the Orion SteadyPix EZ Smartphone Telescope Photo Adapter which makes through-the-eyepiece "afocal" astrophotography extremely easy. The one thing I absolutely love about this solution is that for the visual observer you continue to get the benefits of amazing optical light gathering power of your dobsonian telescope and the benefits of higher-quality eyepieces. I also love the idea that as cell phone camera continues to advance, we continuously benefit from these upgrades that we make regardless of their usefulness in astronomy. The adapter shown above is a GREAT way to dip your toe into the water for astrophotography.
A-focal cell-phone based astrophotography is also very rewarding for people who love to share their experience with others via social media. For many years I have had young people come up to the telescope only marginally interested in viewing with their eyes. The second I showed them how to take an image with their cell phone through the eyepiece, their voices and body language immediately rose to the level of excitement, and the images that they are able to get spark a lasting interest in them for years to come.
However, if you are interested in serious deep-sky astrophotography, consider checking out my other blog post "Which Telescope Should I Buy? It turns out, it really depends..."
Telrad- A Highly Recommended Upgrade Accessory
One of the biggest parts about learning your way around the night sky is to have a high-quality finder-scope. However, another helpful tool is called a Telrad. A Telrad Finderscope uses a red reticle (no magnification) to provide a way to quickly find the location of deep sky objects in the night sky as well as measure the angular distance between objects in the night sky.
I mention my use of the Telrad in EVERY video of my YouTube series "Deep Sky with Dave- Messier Marathon" in which I am going through all 110 Messier Objects. I use the process of star hopping to find deep sky objects without the need for a Go-To telescope computerized mount. This is for me the most rewarding aspect of the process of using a dobsonian telescope, as your really start to become one with the night sky as you learn the constellations, stars, and locations of deep sky objects in your own mind.
~~~WARNING: NOW ENTERING NERDY TECHNICAL ZONE~~~
Don't get super worried if you don't follow this next part completely. Just try to read it and get what you can out of it. It DOES matter and I want you to be informed before you make decisions on your gear.
The telescope in the image (above) was taken of me in 2008, just after getting into astronomy. I was fortunate to spend a few nights next to a very friendly fellow astronomer who let me have more than a few views through this beautiful beast.
Not to go completely off the deep end, I do want to make the case for the benefits of larger telescopes having a significant improvement of both "light grasp" or "light gathering power" as well as an increase in both the magnitude and resolution (how much detail you can see) in your observations. You can try using the calculators at astronomy.tools to learn more about how the effect of telescope size relates between different telescopes.
For example, the difference in Light Gathering power of the XT8 plus (above) at 203mm and the XX12i (below) at 305mm diameter relates to some major gains in capability.
As you can see in the screenshot above from astronomy.tools, the 12" telescope (305mm) is capable of gathering 2.26x (226%) more light than the 8" (203mm) telecope.
The 12" telescope also provides significant increases in resolving power (think resolution like the increase in detail in 4K vs. HDTV) vs. the 8" telescope. In astronomy, this means the ability to separate two objects, like two binary stars for example, from each other when they appear very close to each other in the sky.
As you can see from the screenshots above from astronomy.tools, the 8"telescope can resolve two stars that are 0.68 arc seconds apart (about half the width of Roosevelt's eye on a dime at arm's length) vs. the 12" telescope that can resolve two stars that are 0.45 arc seconds apart. Don't be too overwhelmed by these number if you don't understand them right away, just know that you are getting an view that is theoretically about 1.5x (150%) sharper with the 12" telescope. The reason I say "theoretically" is that the conditions in the atmosphere are nearly always the limiting factor in resolution.
~~~ YOU MADE IT- NOW EXITING: NERDY TECHNICAL ZONE~~~
Drawbacks: Dobsonians are Not Perfect Telescopes
Telescope designs always have drawbacks. One of the biggest drawbacks to the dobsonian design is that they tend to be very large. The reason I suggest jumping directly from the 8" Dobsonian to a 12" dobsonian is due to the fact that at 10" a solid tube dobsonian telescope starts to get pretty big. Unfortunately, the Orion SkyQuest XT10 Plus stars to fall into this category of the (lack) of portability and large weight of these scopes quickly causes them to start collecting dust in your garage, attic, or shed.
There are, however, truss dobsonian designs that provide significant portability. As a result of the truss design, the telescope can be broken down within just a few minutes, providing much lighter-weight components that pack much more easily into a car or for the purpose of storage. I've used a 12" Orion SkyQuest XX12i Intelliscope Telescope for many years and was able to transport that telescope easily in the back of my VW Rabbit/Honda Civic hatchbacks.
I also strongly suggest getting the "travel" kit version of this in the "Orion SkyQuest XX12i and Shroud and Case Set" which will set you back an additional (but totally worth it) $300. Having the piece of mind that you have a proper purpose-built case for your equipment increases the likelihood of you packing that equipment into your car for a trip to that dark sky location.
If you don't want to spend the money up-front, the Shroud and Case Set can be purchased separately for only about $10 more plus shipping at a later date.
"As a result of the truss design, the telescope can be broken down within just a few minutes, providing much lighter-weight components that pack much more easily into a car or for the purpose of storage."
Go-To Telescopes are Overrated In My Opinion
Another drawback of the dobsonian design is that most beginner telescopes are not generally "go-to" and require that you know your way around the night sky. I feel, personally, that getting to know your way around the night sky has never been easier, especially with products like SkySafari that provide the ability to navigate the night sky with your cell phone in real time by simply holding your phone to the sky.
Additionally, I feel that Go-To Telescopes (for the purpose of visual astronomy) are overrated. I would challenge anyone to a night of observational visual astronomy. Me with my dobsonian telescope vs. them with a go-to mount. Knowing my way around the night sky and quickly star-hopping my way to deep sky objects allows me to get MORE viewing in at a faster rate, all while maintaining my night vision as I do not have to look into a screen.
Computerized "Push-To" and Fully "Go-To" Dobsonians Do Exist
Computerized "Push-To" and Fully "Go-To" Dobsonians Do Exist, Albeit at a Premium. A good example of this is the "Intelliscope"series from Orion Telescopes. These telescopes come in a variety of sizes, including the SkyQuest XT8i and SkyQuest XT10i (which I actually do not recommend due to the lack of an upgraded focuser on these scopes). I really wish this scope would truly be an upgrade in all respects from the XT8 Plus and XT10 Plus, but unfortunately that is not the case. Otherwise, I would be recommending these scopes more. I fall back to my recommendation that if you want to get a computerized "Dob" than you should look at the 12" Orion SkyQuest XX12i Intelliscope as your first "entry" level computerized scope, followed by the 14" Orion SkyQuest XX14i Intelliscope.
Truly "Go-To" Dobsonian Telescopes also exist but they tend to start to enter the realm that no longer occupies the "beginner" category based on price and size. Orion makes the 12" Orion SkyQuest XX12G, Orion SkyQuest XX14G, and Orion SkyQuest XX16G. Each of these telescopes is capable of performing a "go-to" to find objects and track them throughout the night for the purpose of visual astronomy and potentially for "lucky imaging" video astronomy for planetary imaging.
However, do not expect tracking performance from these scopes to be capable of doing long-exposure astrophotography. The use of an equatorial platform (wedge) specifically designed to angle the telescope towards the north star, polaris, can provide the ability to make this possible, but the process of perfecting this is very time consuming and expensive. There are much better alternatives for astrophotography. I will be posting more astrophotography-related suggestions in future posts.
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