A Newtonian mirror on a push-to mount
The optics are a standard Newtonian: a parabolic primary mirror at the bottom of the tube and a small flat diagonal mirror near the top that sends the light out the side to the eyepiece. The mount is a box that turns on a ground board, with the tube resting in it on two side bearings. Both motions ride on Teflon pads, so the telescope moves smoothly and stays where you leave it.
Variants add help without changing the optics. Collapsible or Flextube models slide the upper tube down for transport. Tabletop models (Sky-Watcher Heritage) put 5-inch and 6-inch mirrors on a small base for a table or stool. Push-to models such as the Celestron StarSense Explorer use your phone to show where to push; GoTo models (Sky-Watcher Flextube SynScan) add motors and tracking.
An 8-inch f/6 is the sweet spot of size, cost and weight
Dobsonians run from f/4 to f/6. Longer ratios are easier on eyepieces and collimation and give higher power for planets; shorter ones give wider fields but put the eyepiece higher and need better eyepieces.
| Telescope | Aperture | Focal length | Ratio | Obstruction | Resolves | Widest field | Max power |
|---|---|---|---|---|---|---|---|
| Heritage 130 tabletop | 130 mm | 650 mm | f/5.0 | 33% | 0.9" | 2.4° | 260x |
| Heritage 150 tabletop | 150 mm | 750 mm | f/5.0 | 31% | 0.8" | 2.1° | 300x |
| 8-inch f/6 (Classic 200P, AD8) | 203 mm | 1,200 mm | f/5.9 | 23% | 0.6" | 2.2° | 350x |
| 10-inch f/4.7 (Classic 250P) | 254 mm | 1,200 mm | f/4.7 | 23% | 0.5" | 2.2° | 350x |
| 12-inch f/5 (Flextube 300P) | 305 mm | 1,500 mm | f/4.9 | 21% | 0.4" | 1.8° | 350x |
| 16-inch f/4.5 truss | 406 mm | 1,830 mm | f/4.5 | 20% | 0.3" | 1.4° | 350x |
Obstruction figures are approximate, as a share of the aperture's diameter. Widest true field uses the largest eyepiece the focuser takes: a 46 mm field stop for 2-inch focusers, 27 mm for 1.25-inch. Highest useful power is 2x per millimeter of aperture, capped at 350x by the air.
Current Dobsonians from Sky-Watcher, Apertura and Celestron
Nearly every Dobsonian under $2,000 is made by Synta (Sky-Watcher) or GSO (Apertura) in China and Taiwan.
| Model | Maker | Aperture | Ratio | US price | Notes |
|---|---|---|---|---|---|
| Heritage 130 | Sky-Watcher | 130 mm | f/5 | $269 to $305 | Tabletop; collapsible |
| Heritage 150 | Sky-Watcher | 150 mm | f/5 | $309 to $355 | Tabletop; collapsible |
| StarSense Explorer 130 tabletop | Celestron | 130 mm | f/5 | $480 | Phone-guided push-to |
| Classic 150P | Sky-Watcher | 150 mm | f/8 | $449 to $515 | Floor-standing; long focus for planets |
| Classic 200P | Sky-Watcher | 203 mm | f/5.9 | $629 to $725 | The standard 8-inch |
| AD8 | Apertura | 203 mm | f/5.9 | about $725 | Dual-speed focuser, two eyepieces, laser collimator, cooling fan |
| StarSense Explorer 8-inch | Celestron | 203 mm | f/5.9 | $879 | Phone-guided push-to |
| Flextube 200P | Sky-Watcher | 203 mm | f/5.9 | $739 to $850 | Collapsible tube |
| Classic 250P | Sky-Watcher | 254 mm | f/4.7 | $869 to $995 | 10-inch solid tube |
| Flextube 250P | Sky-Watcher | 254 mm | f/4.7 | $999 to $1,150 | Collapsible 10-inch |
| StarSense Explorer 10-inch | Celestron | 254 mm | f/4.7 | $1,199 | Phone-guided push-to |
| AD12 | Apertura | 305 mm | f/5 | about $1,250 | 12-inch solid tube |
| Flextube 300P | Sky-Watcher | 305 mm | f/4.9 | $1,649 to $1,895 | Collapsible 12-inch |
| StarSense Explorer 12-inch | Celestron | 305 mm | f/4.9 | $1,599 | Phone-guided push-to |
| Flextube 250P SynScan | Sky-Watcher | 254 mm | f/4.7 | $1,649 to $1,895 | GoTo and tracking |
Prices are from US dealers in November 2026; tariffs on Chinese-made optics raised most prices in 2025.
Best for galaxies, nebulae and clusters; workable for planets
A Dobsonian is the best visual deep-sky telescope for the money: an 8-inch reaches all 110 Messier objects from a dark site and 95 from the suburbs, and a 12-inch reaches all 110 from a dark site and 107 from the suburbs. On planets, an 8-inch f/6 matches a Schmidt-Cassegrain of the same size once it has cooled; without tracking you nudge it every 30 to 60 seconds at 200x.
The limits are bulk and manual tracking. The base of an 8-inch is about 2 feet across and the tube about 4 feet long. Basic Dobsonians are poor for astrophotography beyond the Moon and planets, because they do not track the sky. Newtonian mirrors also need collimation, an alignment check with a laser or Cheshire tool, every few sessions.