The Beginner’s Guide to Dobsonian Telescopes
When it comes to buying your first telescope there’s a lot to consider but not a whole lot of clarity in advice. A friend may mention that you’ll want an aperture of one size, or a focal length no less than 300 mm, or you might be advised simply to buy a Dobsonian.
You say “Sure, I’ll check that out,” and proceed to walk away, still uncertain of what to look for. We at OPT are here to help guide you through the complexities of finding a telescope perfect for you, and this beginner’s guide to is a perfect place to start.
THE INS AND OUTS OF A "DOB"
Due to the ease of use provided by the Dobsonian mount, amateur astronomers find this design ideal for ramping up their efforts in observing in the cosmos. The design is so simple that even those with minimal knowledge or skill could build one of their own without much trouble, but it’s near impossible to replace the precision and quality of professionally manufactured telescopes
The baseline design is comprised of a turntable Alt-Az mount, a Newtonian reflecting telescope with varying aperture and focal length, and an eyepiece. These are the very basics of course, and the one you purchase may already come with a finder scope or onboard computer.
WHAT'S GOOD ABOUT THIS TELESCOPE TYPE?
One of the best qualities of the Dobsonian telescopes is their versatility. Whether you’re wanting to just casually view the night sky in a point-and-look manner, or you’re in the mood to scout out a distant object, this design will work for you.
When it comes to the weight of these scopes, we're talking anywhere between 5 and 200 pounds! Even those on the higher end are still considered portable as they can be taken apart and transported. If you're worried that a Dob might be too heavy for you, fear not! Anybody can find a scope weight that works for them.
WHEN TO USE DOBSONIAN TELESCOPES?
NEAR SPACE OBJECTS – THE MOON, PLANETS… THE SUN
Thanks to the ease of the alt-azimuth mount and the wide field of view (FoV) generally provided by these models, they’re a perfect fit for amateur astronomers on a night of visual observing. We can twist and turn the scope to the Moon, to Mars, and the stars.
DEEP SPACE OBJECTS (DSOS) – GALAXIES, NEBULAE… QUASARS
Dobs are equipped for viewing these further and fainter objects as well, although tracking these can be quite a challenge without a properly integrated system. In general, finding any object in the night sky shouldn’t take much effort at all for one of these.
WHY A DOBSONIAN ?
That’s the question. Why would you want to use a Dobsonian telescope over other styles? Here are some points to consider:
- Reasonable pricing for a high-quality product
- Great scopes without creating a vacuum in your bank account!
- Easy setup and use for beginner and amateur astronomers!
- From box to backyard a Dob can be up and running in just a few minutes!
- Portable by design with highly varied weights and sizes
- No image distortion from chromatic aberration
- Refracting telescopes can get light distortion from its lens design, but that won't happen with one of these reflectors
- Well adapted for professional use, these models range from child’s play all the way to the big leagues.
HOW TO USE DOBSONIAN TELESCOPES?
Just point and take a look! These are among the simplest designs around for telescopes. Once assembled it requires no more than the point-and-look method—unless, of course, the eager astronomer in you opts for one with tracking technology. If that’s the case, follow the instructions provided and you’re ready to scour the skies.
This type of telescope are generally not used for astrophotography purposes. This is in large part due to the Alt-Az mount they’re known for, which can prove too clunky especially when attempting to capture deep space objects. For that purpose, a telescope with an equatorial mount would serve better. Nonetheless, a Dobsonian certainly can be used for astrophotography on a more local scale such as our neighboring planets and the Moon.
COLLIMATING A TELESCOPE
Collimating? Collimation? What’s that? It’s a fancy (technical) word for aligning the mirrors within a telescope. This need not be a hassle either with help from one of many collimation tools available. Simply attach the collimator to the eyepiece port and adjust the mirror knobs on your telescope until aligned.
Now you might also be wondering: why would I need to realign my mirrors? Why do the mirrors lose their alignment? Great questions again. We can think of the mirrors like strings on a guitar, and we all know the necessity of tuning that guitar properly. The same necessity applies to your telescope, but instead of tuning for a sound we’re tuning for a sight. Everything we love in life requires a little maintenance and our scopes are no different.
WHICH ONE TO BUY?
Best Portable – Celestron FirstScope Signature Series Moon
This first scope is the ultimate in portability and ease of use. Small and lightweight enough to fit into an adult backpack, this telescope is ideal for convenience and family use at an extremely affordable price.
Best Value – Meade EclipseView 114 mm Reflecting Telescope
The Meade EclipseView 114 mm Reflecting Telescope is an excellent choice for the aspiring astronomer looking to get just a bit more serious in their stargazing. Slightly bigger than the previous telescope, the EclipseView will enable a keener eye to the sky. As a bonus, this telescope is ready to use for viewing the sun with the removable solar filter that’s included.
Best GoTo – Orion SkyQuest XT8i Intelliscope Telescope
Now we get to the first of the more big-league telescopes. The Orion SkyQuest XT81 is for those looking to get serious in astronomy. Able to get up close and personal with deep-sky objects like nebulae and galaxies but also staying intimate with our own moon, this telescope will literally guide you through the cosmos with its built-in computer database.
Best Large Size – Sky-Watcher 20” Stargate Truss-Tube Go-To
The final item on the list and it sure is a big one! Weighing in at a total of 164 pounds when fully assembled, this Sky-Watcher 20” is sure to turn some heads wherever it is. The most advanced in its class, this telescope is immensely powerful and provides refined detail when scouring deep space. The computer database provides 42,900 objects that can be located and tracked with the motorized mount. If you’re looking to go big, this is your Go-To.
Recommended Accessories for Dob Owners
Telrad Finder Scope with Mounting Base
With any non-computerized telescope, we are better off having a finder scope attached to the tube. Finding what we want to look at would be too much of a hassle without one. It would be like looking for your keys without turning on the light: sure, we can find them, but why make it more difficult?
TPO Newtonian Laser Collimator III
Whether you’re into the challenge of looking without a finder scope or not, this is an essential tool in any reflecting telescope setup. As mentioned earlier, collimating your scope is necessary for viewing crisp images. Most collimation tools will be acceptable but the TPO Newtonian at the top of its class, and that’s why we put it here.
We hope this guide has helped with any questions you’ve had regarding Dobsonian telescopes, and we wish you the best in exploring the cosmos. May your skies be forever clear.
Alt-Azimuth (Alt-Az) Mount – What this term describes is no more than a mount able to move up, down, and side-to-side with ease. Due to the varying sizes of Dobsonians, these can be small or quite bulky to support a larger telescope.
Newtonian Reflecting Telescope – A telescope using multiple curved mirrors within the tube to reflect and refine the light image we’re viewing.
Focal Length – The distance between the primary lens and the focus point in a telescope. Generally, the longer the focal length the more magnification and focus a scope will have (although this varies based on telescope type).
Eyepiece – This is where you put your eye.