Sky-Watcher Flextube 8-inch Dobsonian: Review

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The author at the eyepiece of the 8-inch Sky-Watcher Flextube Dobsonian in the solstice twilight of his high-latitude home. Credit: Alan Dyer

If you’re looking for the best value in a telescope, offering maximum aperture on a steady, easy-to-use mount, look no further than a Dobsonian reflector. Sky-Watcher offers both Classic solid-tube “Dobs” and, for a modest price increase, collapsible Flextube models. I think the upgrade is well worth the price. The collapsible tube makes the telescope easier to transport, and the tube finish looks more polished. 

In selecting telescopes to test and feature in the new edition of The Backyard Astronomer’s Guide, in late 2019 I purchased an 8-inch (200 mm) Flextube 200P for its combination of generous aperture without being too heavy and unwieldy, as even the larger Flextube scopes can become. 

I was so impressed with the telescope, I decided to keep the Flextube as my main visual scope for both deep-sky and planetary observing. It really is a pleasure to use.

The Sky-Watcher Flextube 200P with a 2-inch eyepiece and the magnetic counterweight described in the text. Current telescopes have white mounts. Credit Alan Dyer

Flextube Features

First, the optics are superb. For a mass-market telescope the f/6 mirror is remarkable, showing nearly textbook perfect images in a critical star test. There’s no astigmatism or spherical aberration. Under good seeing conditions, planetary images are very sharp and detailed. I used it a lot in late 2020 for fine Mars views. 

In side-by-side tests with a 12.5-inch MAG1 Portaball with premium Zambuto optics, the Flextube performed admirably, providing similar views of Mars. Credit: Alan Dyer

The optics were in perfect collimation out of the box and I’ve never had to touch it, despite the telescope spending most of its time outside under cover subject to extremes of temperature. 

The optics also stay in collimation when sliding the upper end down for storage, then extending it back up and locking it into position for observing. There’s no shroud to cover the open truss tube. If stray light, dust or heavy dew proves to be a problem at your site, a shroud is available from AstroZap. (See https://astrozap.com/products/sky-watcher-light-shroud

The collapsing upper end shortens the tube by 11 inches (28 cm) for storage. While not as compact as a full truss-tube Dobsonian, the Flextube is much less fuss to set up. Credit: Alan Dyer

The mount moves very smoothly in both axes, making it easy to follow objects – remember, no-frills Dobsonians have no tracking ability. I did have to initially adjust the tension of the azimuth motion by tightening the bolt in the middle of the ground board. The altitude tension can be adjusted more easily by using the hand knob on the eyepiece side of the mount. 

The focuser is a Crayford design with a smooth, backlash-free motion. It isn’t a dual-speed or premium “Feathertouch” style, but it does the job well. However, switching from 2-inch to 1.25-inch eyepieces is annoying. To do so, you have to keep switching between the two supplied adapters. Use one or the other, but not both! 

Each clamps into the focuser, and are critical parts easy to misplace. If you have a 1.25-inch step-down adapter from another telescope, it can be used with the 2-inch adapter, allowing it to stay in place. 

The four-vane spider is solid and the primary mirror is center-marked for ease of collimation. A knob near the eyepiece aids in moving the telescope. Credit: Alan Dyer

Flextube Shortcomings

Two eyepieces are included, a 25mm (48x) and 10mm (120x), both Super Plössl designs with standard 50° fields and short eye relief. While they are decent, you’ll soon want to replace them with better quality models, especially 2-inch eyepieces to take advantage of the wide field of view the telescope and focuser can provide, and higher power eyepieces with longer, more comfortable eye relief. 

The finderscope included with my unit was an 8×50 right-angle model. There’s nothing wrong with the finder; it works very well. I’m just not a fan of right-angle finders – I find their mirror-reversed views, and the fact you aren’t sighting in the same direction as you are aiming, makes them difficult to use for more than just the brightest targets. However, the telescope is now advertised as coming with a right-angle correct-image (RACI) finder, meaning it is not mirror-reversed.

I switched to a straight-through finder I had on hand, or I often just use a red dot finder instead. I also bought a dual-finder base from Orion (see https://www.telescope.com/Orion/Orion-Dual-Finder-Scope-Mounting-Bracket/rc/2160/p/102788.uts) that accepts both the red dot and optical finder. 

The focuser tension can be adjusted, but changing eyepiece sizes requires swapping the two supplied focuser adapters (2-inch and 1.25-inch), an inconvenience. Credit: Alan Dyer

However, adding any more components to the upper end, or using heavy 2-inch eyepieces exposes a weakness of the telescope. It tends to be top heavy. Lessening the altitude tension for ease of motion can result in the telescope drifting down, especially when aimed low. Tightening the tension stops the sinking but spoils the smooth motion. 

To improve the balance and motion, I bought a 1-lb. magnetic counterweight. (See https://www.telescope.com/Orion-Magnetic-1-Pound-Dobsonian-Counterweight/p/130844.uts) Beanbags stuck to the tube might work just as well, but the magnetic weight keeps the fine finish of the metal tube clean and does the trick. The altitude tension can then be set once, even when swapping out eyepieces. 

Recommendations

I find the Sky-Watcher Flextube 200P offers a great combination of aperture, portability and, at $575, price. But this is no cheap, light-bucket scope. The optics are good enough for superb planetary views, as well as deep-sky vistas. While the price is attractive, budget for a few upgrades. 

If you do want the luxury of GoTo pointing, this same scope is available as the SynScan 200P, with dual-axis motors and a computer hand controller with WiFi. But the cost increases to $1,165. The high-tech components can’t be added later as an upgrade, so chose wisely. 

But I like and recommend the basic model, for the pleasure of keeping it simple under the stars and not fussing with power supplies and computers. 

Plus: Excellent optics; sturdy mount with smooth motions
Minus: Can be top heavy requiring the addition of a counterweight

MSRP: $575 (Classic solid tube version is $485; SynScan GoTo version is $1,165)
Website: https://www.skywatcherusa.com/

 

About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at www.amazingsky.com has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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