Trying to determine what telescope is the best fit when comparing a Dobsonian and Newtonian telescope is head-scratching. Both telescopes are reflector telescopes, so the fundamental design is similar.
It’s hard to go wrong with either telescope, but each has pros and cons. Let’s peel back the lens cover and look inside the telescope to help you make the best choice.
Dobsonian vs. Newtonian Telescope: Side-by-Side Comparison
| Dobsonian Telescope | Newtonian Telescope | |
|---|---|---|
| Optical Lenses? | No | No |
| Optics | The telescope uses mirrors to focus and bend light | The telescope uses mirrors to focus and bend light |
| Mount | Altazimuth, generally manual telescope movement | Equatorial or altazimuth, computerized telescope movement |
| Tracking | Manual | Motorized or manual |
| Tripod? | No | Yes |
| Mirrors? | Yes | Yes |
| Focal Length (mm) (8” Telescope) | 1000 | 8000 |
| Focal Ratio (8” Telescope) | f/8.77 | f/4 |
| Aperture (mm) (8” Telescope) | 114 | 203 |
| Best Use | Deep space observation | Deep space observation |
| Maintenance? | Yes, collimation | Yes, collimation |
| Cost | Less expensive | More expensive |
| Astrophotography? | Somewhat suitable for non-tracking exposures | Yes |
Fantastic Bundle Kit
Orion SkyQuest XT8 Classic Dobsonian Telescope Kit
- Simple hands-on, point-and-view navigation without complicating counterweights, gears, clutches, polar alignment, or the need to balance the tube
- Large 8"-diameter parabolic mirror excels for deep-sky viewing of nebulas, galaxies, and star clusters, and serves up jaw-dropping views of the planets and Moon
- Features a precision 2" Crayford focuser with 1.25" adapter, allowing the use of 1.25" eyepieces or optional 2" eyepieces
- Stable Dobsonian base provides vibration-free images even when viewing at a high power, and features smooth motions to make manual tracking of celestial objects a breeze
- Includes: Orion Shorty 2x Barlow (for double the magnification), Orion‘s MoonMap 260, DeepMap 600, and Telescope Observer‘s Guide, a RedBeam Mini flashlight, and a smartphone photo adapter for taking pictures through the telescope‘s eyepiece
Top-Notch Control
Celestron NexStar 130SLT Computerized Telescope
- Computerized hand control with a 4,000-object database
- Compact and portable
- Newtonian reflector optical design
- SkyAlign technology
- 130mm aperture
What’s a Reflector Telescope?
Both Dobsonian and Newtonian telescopes are types of reflector telescopes. But what exactly is a reflector telescope?
Reflecting telescopes utilize mirrors to direct and shape the light entering the telescope. The telescope mirrors will need to be routinely adjusted to correct for chromatic aberration.
Let‘s break it down more below.
Reflector Telescope Invention
Isaac Newton studied telescopes with lenses and determined that astronomers would not eliminate chromatic aberration with the optical lens configuration. Newton used mirrors instead of lenses to bend and shape the light that entered the telescope. While Newton is often credited with the reflector telescope‘s invention, he was building on a design created by James Gregory.
Newton experimented with speculum metal in his spherical mirror design. Speculum metal is made from copper and tin and is similar to bronze. Newton added arsenic to the mix, believing that would make the metal more reflecting.
A kiln heated the metal at approximately 1830°F. The metal was cast into a mold once it was molten. After cooling, the concave-shaped metal mirror must be ground and polished to a high sheen. To smooth and polish the mirror requires a grinding disk with the exact opposite (convex) shape than the mirror. The mirrors tarnished quickly and often needed to be removed and polished.
Today, telescope mirrors are glass ground into the proper shape and subsequently coated (deposited) with a thin layer of silver or aluminum.
How Does a Reflector Telescope Work?
Light entering a reflective telescope passes through the body of the telescope and strikes a primary mirror at the back of the telescope. The mirror redirects the light back up the telescope. A slight mirror curvature turns the light towards a smaller secondary mirror at the other end of the telescope. When the light strikes the secondary mirror, a perfectly focused miniature image will appear on the mirror face if the telescope is aligned correctly. A reflected image appears on the eyepiece.
Collimation
Hobbist-level Newtonian reflector telescopes are generally lightweight and designed to be moved from location to location. No matter how careful you are, you‘ll jiggle the mirrors when you move a reflector telescope around. The output image is defocused and blurry when mirrors require collimation inside the telescope.
A laser passes through the optical path to aid in aligning the telescope‘s mirrors. ©luchschenF/Shutterstock.com
Dobsonian vs. Newtonian Telescope: What’s the Difference?
Dobsonian and Newtonian telescopes utilize the design principles of a reflecting telescope.
A Newtonian telescope refers to a specific type of reflector telescope. A Dobsonian telescope generally, but not always, refers to a Newtonian telescope sitting on top of a tripod and mount.
There are vital differences between a Dobsonian and Newtonian telescope, however, like the telescope‘s size, mount, focal length, and precision object tracking. A Dobsonian telescope is big and bulky, so it (generally) sits on a rotating base at ground level. Big and bulky pay dividends in higher magnification and long focal lengths.
A Dobsonian isn’t necessarily the telescope you want to dismantle and take camping over the weekend. A Newtonian telescope is smaller in stature than a Dobsonian but is excellent for dismantling and taking to your favorite dark sky location. A Dobsonian is the preferred choice for deep-space observation.
With all that being said, let’s take a closer look at their differences.
Size
A Dobsonian telescope is roughly two to three times the length of a Newtonian. A Dobsonian sits on a cradle (base) that’s positioned very close to the ground. A typical Dobsonian is between four to six feet in length. There are tabletop Dobsonian telescopes that are a good fit for beginner astronomers. Non-tabletop Dobsonians require a space commitment, like an entire closet.
A Newtonian telescope is shorter than a Dobsonian. The tripod and the mount limit the length of the telescope. If the telescope is too long, it won’t be able to aim “up” very far. A Newtonian telescope is portable and easily packed away in the corner of a closet or trunk.
Let‘s examine reflecting telescopes and telescope mounts.
Telescope Mounts
In a nutshell, telescopes sit atop a mount. A mount secures the telescope to a base. The base is either a tripod or a flat structure that sits directly on the ground.
The telescope rotates up, down, and round in a circle on the mount or base. Selecting a mount that meets your needs is critical in telescope selection.
Let‘s take a look at the two primary telescope mounts.
Altazimuth Mount: Dobsonian Telescope
The altazimuth mount moves in two directions: up and down from 0° to 90° (altitude) and a complete 360°(azimuth.) Altazimuth mounts are common on Dobsonian telescopes. Dobsonian telescopes are (generally) mounted on a flat rotating base. Altazimuth mounts are not the best choice for deep-space astrophotography.
An altazimuth mount is ideal for astronomy beginners. A telescope with a motorized altazimuth mount can easily be aligned to a few stars and move automatically to most stars and galaxies. An altazimuth mount doesn’t correct for the exact movement of the Earth. An equatorial mount is the better choice when precise telescope movement is critical.
Great Altazimuth Option
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- Limited Edition
- Dobsonian bundle
- 203 millimeters objective lens diameter
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A good telescope mount may cost 2X the telescope‘s cost. ©nikkytok/Shutterstock.com
Equatorial Mount: Newtonian Telescope
An equatorial mount is aligned to the Earth’s rotation axis via the celestial north pole. An equatorial mount corrects for vertical movements (altitude) with declination (Dec) and horizontal (azimuth) with right ascension (RA). A telescope can automatically track objects moving through the night skies after alignment to the celestial north pole.
Focal Length
A Dobsonian telescope has a longer focal length than a Newtonian. Dobsonians are sitting in a cradle near the ground. As a result, a Dobsonian is much longer than a Newtonian. The long focal length makes the Dobsonian a good choice for viewing the planets or moon at high magnifications.
A Newtonian telescope has a shorter focal length than a Dobsonian. A Newtonian sits on a mount secured to the top of a tripod. The telescope resides on top of the tripod, several feet above the ground.
Newtonians are shorter than Dobsonians, so their focal length is less than a Newtonian. The shorter focal length but larger aperture make the Newtonian a good option for deep-space observation or astrophotography.
The focal length of a telescope impacts its magnification. ©Lambros Kazan/Shutterstock.com
Precision Object Tracking
Looking at the night skies, it appears that the stars, planets, and galaxies are all moving. In actuality, they’re not moving; the Earth is moving.
Generally, Dobsonian telescopes use an altazimuth mount. Suppose you find Mars in the eyepiece and lock the telescope movement. You can watch Mars move across the telescope eyepiece window as the Earth rotates. In a few mere seconds, Mars will no longer be in your viewfinder. Dobsonian telescope uses an Altazimuth mount, so the ability to track stars or galaxies automatically could be better.
A Newtonian telescope uses an equatorial mount. The telescope automatically adjusts the direction the telescope is aiming. You can aim the telescope at Mars (after the telescope is polar aligned), and Mars will remain in the viewfinder window throughout the night. You can grab snacks and a blanket, and the telescope will remain fixed on Mars. The ability to track with an equatorial mount is a crucial performance from a Newtonian telescope.
Dobsonian vs. Newtonian Telescope: 8 Must-Know Facts
- Dobsonian and Newtonian telescopes are reflector telescopes.
- Dobsonian telescopes use an altazimuth mount. An altazimuth mount is a good choice if you take something other than long-exposure astrophotography images. An altazimuth mount allows you to place the telescope onto the support and not worry about polar alignment.
- Newtonian telescopes use an equatorial mount. An equatorial mount is an advanced mount for astronomers who are willing to spend longer setting up the telescope each (and every) time they use it.
- A Dobsonian telescope may not properly connect to an equatorial mount. A Newtonian telescope may not mount correctly to an altazimuth mount. Read the fine print carefully.
- You‘re in charge of the “telescope tracking” with a Dobsonian telescope and a non-motorized Altazimuth mount. There is no motorized mount, so you must adjust the telescope’s direction to keep the object of interest in the center of the eyepiece field of view. Based on our experience with telescopes, it’s not a reasonable expectation to be able to move a telescope for deep space observation manually and keep the object of interest centered in the viewfinder.
- Commercial products can mount a Dobsonian telescope onto an equatorial platform but may cost several thousand dollars. You may be better served to purchase a Newtonian telescope with an equatorial mount right out of the gate.
- The equatorial mount of a Newtonian telescope enables the telescope to track objects as they move through the night skies automatically. A Newtonian telescope with an equatorial mount is a good choice for deep-space observation and astrophotography.
- A Newtonian telescope with an equatorial mount requires polar alignment.
Fantastic Bundle Kit
Orion SkyQuest XT8 Classic Dobsonian Telescope Kit
- Simple hands-on, point-and-view navigation without complicating counterweights, gears, clutches, polar alignment, or the need to balance the tube
- Large 8"-diameter parabolic mirror excels for deep-sky viewing of nebulas, galaxies, and star clusters, and serves up jaw-dropping views of the planets and Moon
- Features a precision 2" Crayford focuser with 1.25" adapter, allowing the use of 1.25" eyepieces or optional 2" eyepieces
- Stable Dobsonian base provides vibration-free images even when viewing at a high power, and features smooth motions to make manual tracking of celestial objects a breeze
- Includes: Orion Shorty 2x Barlow (for double the magnification), Orion‘s MoonMap 260, DeepMap 600, and Telescope Observer‘s Guide, a RedBeam Mini flashlight, and a smartphone photo adapter for taking pictures through the telescope‘s eyepiece
Top-Notch Control
Celestron NexStar 130SLT Computerized Telescope
- Computerized hand control with a 4,000-object database
- Compact and portable
- Newtonian reflector optical design
- SkyAlign technology
- 130mm aperture
Dobsonian vs. Newtonian Telescope: Which One is Better for You?
The best telescope for you is the one you‘ll use the most often. Purchasing a telescope that doesn’t meet your needs is a recipe for a telescope getting dusty in the closet.
Dobsonian telescopes are much larger and less portable than Newtonian’s. A Dobsonian (generally) rests in a cradle on the ground. A Dobsonian telescope is quite long. As the mirror’s size increases, the telescope’s length proportionally increases.
Newtonian telescopes have a tripod and an equatorial mount (sometimes an altazimuth) and are easy to dismantle and toss in the backseat of the car. Newtonian telescopes tend to be shorter than Dobsonian but have motorized mounts that make star tracking a breeze. A Newtonian, with an equatorial mount, is designed for deep-space observation.
You‘ll absolutely want a quality mount, counterweights, and tripod to eliminate vibration that will impact astrophotography, so be sure to do your research and figure out what‘s best for your unique needs.
The image featured at the top of this post is ©AstroStar/Shutterstock.com.