The Optical Tube
The 10” FlexTube is a 10” (254mm) f/4.7 Newtonian reflector with a focal length of 1200mm. While the included 25mm Plossl eyepiece works well enough for low power, I’ve noticed that more affordable wide-angle eyepieces like “SuperView” or “SWA” exhibit edge-of-field astigmatism and field curvature at f/4.7. Low-power eyepieces with a field stop wider than the included 25mm Plossl will also have noticeable coma around the edges of the field of view – though other aberrations such as astigmatism may mask it. It’s important to take this into account when shopping for eyepieces as cheaper wide-angle models may not offer the best performance and could be a waste of money when used in conjunction with this telescope.
The 10” FlexTube GoTo of course features Sky-Watcher’s FlexTube collapsible tube system, which allows the tube to retract from its normal length of 44” to 32”. What do you gain from this? In actuality, not much. I find the 44” tube already short enough to fit in most vehicles, and the FlexTube design makes no difference in the overall weight of the telescope’s tube compared to a conventional solid-tubed design. You also will need a shroud to cover the exposed section of the tube and keep out stray light, and collimation adjustment might be required a bit more frequently.
Collimation of the 10” FlexTube’s primary mirror can be adjusted with standard hand knobs at the back, while secondary adjustment requires a hex key; collimation is a fairly straightforward process, and our collimation guide provides more information. Swapping the secondary mirror’s hex screws for thumb screws is unnecessary and will likely lead to more collimation shift. The trusses have a second setting providing enough in-focus travel for binoviewer or camera use, and both 1.25” and 2” extension tubes are provided as is typical with Sky-Watcher’s Dobsonians.
Attaching the 10” FlexTube GoTo to its Dobsonian Base is fairly straightforward – simply rotate the left side bearing holder into place, lower it onto the base horizontally, and tighten one knob for secure attachment.
Accessories
The 10” FlexTube GoTo Dobsonian comes with 1.25” 25mm (48x) and 10mm (120x) “Super Plossl” oculars, which are decently well-corrected but have a narrow 50-degree apparent field of view. This means that there won’t be any issues with coma or astigmatism, though they are not the best eyepieces to use given the size and cost of this scope. The 10mm, being a Plossl, is also fairly short on eye relief, requiring you to jam your eye into the lens to take in the full field of view.
As with the other Sky-Watcher Dobsonians, the typical separate 1.25” and 2” extension tubes supplied, which are required to reach focus, are of very low quality, will mark up your eyepieces and don’t allow for the attachment of filters. They can also interfere with the accuracy of a laser collimator; replacing them would be a good idea.
For aiming and alignment purposes, this telescope includes a 9×50 straight-through finder scope with crosshairs offering an approximately 6-degree true field and an upside-down view just like you see through the telescope itself. Although overkill for aligning the scope’s GoTo system, it is not as user-friendly or comfortable to look through as a right-angle finder or reflex sight. Fortunately, replacing it with either alternative is simple, thanks to its standard Synta/Vixen-style finder shoe.
Mount
As with most GoTo Dobsonians, the 10” FlexTube GoTo Dobsonian uses an alt-azimuth Dobsonian mount made mostly out of particle board with servo motors and slip clutches attached. The altitude axis uses a motorized bearing on one side which you clamp the scope to, with a traditional Dobsonian bearing on the other side to hold the remaining weight and minimize the power needed to move the scope around. The slip clutches on both the altitude and azimuth axis can be unlocked and allow you to freely aim the scope around the sky, while Sky-Watcher’s FreedomFind dual encoders keep track of where the scope is pointed allowing for no interruption of tracking and pointing capabilities. The motorized kit does make the 10” FlexTube GoTo’s Dobsonian base a bit heavier than its manual counterpart, which can be something to consider – at 39 lbs vs. the manual scope’s 27 lbs, lifting it can be a bit of a chore.
Depending on which version you buy, the 10” FlexTube GoTo Dobsonian comes with either a SynScan hand controller or a WiFi dongle, allowing you to control it via the SynScan app which can be coupled to SkySafari Pro for easy pointing on your smartphone or tablet. Given the simpler interface of the app and the lower price of the WiFi version we would probably recommend it over the SynScan hand controller, which can be a little more difficult to navigate and set up.
Should I buy a Used Sky-Watcher 10” FlexTube GoTo Dobsonian?
A used 10” FlexTube GoTo Dobsonian has a fair amount of things that can go wrong – any damage to the base can render the GoTo system inoperable and you should of course make sure that the electronics work. The poles should collapse and extend smoothly, and of course any corrosion to the primary and secondary mirrors can necessitate a recoat which may or may not be worth the cost compared to simply buying a new scope instead of a damaged used unit. However, a used 10” FlexTube GoTo in good shape can last you a lifetime.
Alternative Recommendations
The 10’ FlexTube GoTo Dobsonian is certainly one of the better Dobsonians in its size range available and certainly the best 10” GoTo. However, you may want to consider a few alternative options.
Under $1500
- The Zhumell Z12/Apertura AD12/Orion Skyline 12’s large 12” aperture gives it significantly more light-gathering and resolving power than a 10” scope and the provided accessory package is quite good – however, it’s rather heavy/bulky on account on its massive solid tube.
- The Zhumell Z10/Apertura AD10/Orion Skyline 10 is an affordable 10” Dobsonian packed with features and accessories, offering some of the best value for the money of any telescope of this aperture.
- The Celestron StarSense Explorer 10” Dobsonian’s lightweight base and StarSense Explorer technology make it quick to set up and a breeze to use, though the scope lacks anything but the most basic accessories and features to get you started out with and the price is a little steep.
- The Explore Scientific 10″ Hybrid Dobsonian’s extremely compact truss tube design makes it far more portable than other 10” Dobsonians and at a price that can’t be beat. The all-metal design also features no particle board components. However, you’ll need to spend some time and money tweaking this scope for it to perform well.
$1500-$2500
- The Sky-Watcher 12″ Flextube Collapsible Dobsonian is essentially a scaled-up 10” FlexTube but the collapsible tube provides significantly more space savings at this aperture. This can make a huge difference for portability, though the manual Sky-Watcher Dobsonians aren’t exactly known for having the most well-designed and smooth mounts. The GoTo version of the 12” FlexTube has the same features as the 10” model and is an even better choice.
- The Explore Scientific 12″ Truss Tube Dobsonian is extremely compact when disassembled and features an all-metal design, built-in fans and a dual-speed Crayford focuser. However, it comes with no usable accessories to start out with.
- The Orion SkyQuest XT10G GoTo Dobsonian is identical to the 10” FlexTube GoTo Dobsonian in design and function apart from of course a solid tube, a dual-speed 2” Crayford focuser and a slightly different set of accessories.
- The Celestron NexStar Evolution 8” isn’t quite as capable as a 10” Dobsonian on account of its smaller aperture and long focal length, but it still has plenty of light-collecting and resolving power, is extremely compact, and features built-in WiFi and an onboard lithium battery as well as some astrophotography capabilities which a GoTo Dobsonian cannot attain.
$2500+
- The Orion SkyQuest XX14i Dobsonian’s huge 14” primary mirror blows away the views through a smaller 10” or 12” while the IntelliScope digital setting circles help you to find your way around the sky. However, despite its truss tube, it is quite big and you should really have a smaller telescope to accompany it.
- The Orion SkyQuest XX12G Dobsonian has the same GoTo mechanics and features as the Sky-Watcher GoTo Dobsonians but its full truss tube makes it more portable than the 12” FlexTube, albeit more complicated to assemble.
- The Sky-Watcher 12” FlexTube GoTo Dobsonian features the same overall design and features of the 10” model but of course with additional aperture, while still remaining fairly portable and convenient, if a bit heavier than the 10” FlexTube GoTo or the manual 12” model.
Aftermarket Accessory Recommendations
A shroud is essential for the 10” FlexTube Dobsonian model. Without one, light can enter the tube and on damp nights dew can more easily cause your optics to fog up. Additionally, there is a greater chance of something being dropped or smudged on the optics due to an unprotected tube. You can buy a pre-made shroud or make one from fabrics such as Ripstop Nylon, Lycra, or Spandex.
The included 9×50 right-angle correct-image finder on the 10” FlexTube Dobsonian can get you by on its own, but a zero-power reflex sight is a great addition or replacement. The Rigel Quikfinder mounts easily to the tube and is lightweight, while the Explore Scientific ReflexSight will fit on the scope’s stock finder bracket in place of the 9×50. Bulkier options like the Telrad or QuInsight must be placed where they don’t interfere with hardware and knobs. All of these finderscope options offer a “bull’s eye” reticle view with no power needed, and each have their own strengths and weaknesses.
As previously mentioned, you should really replace the 1.25” and 2” extension tubes provided with the 10” FlexTube with a single 2” extension tube and 1.25” adapter using compression rings and with filter threads, which will allow you to attach 2” filters to 1.25” eyepieces and keep the same filter installed when changing magnifications. You’ll also need a collimation tool, such as a Cheshire, for collimating the scope as nothing is provided by default. Our collimation guide explains in more detail.
Both of the 10” FlexTube’s provided eyepieces are adequate, but you may want to consider some additional ones for higher or lower magnifications. For example, a 15mm SWA or redline eyepiece (80x magnification) would be great for bridging the gap between what the stock eyepieces provide. Additionally, a high-power planetary eyepiece such as the Astromania 4.5mm (267x) is perfect for close up views of the moon, planets and double stars on a clear night. The 2” Apertura 32mm SWA (38x) or 24mm Explore Scientific 82-degree (50x) is ideal for unlocking a wide low-power field of view, and you may wish to add a coma corrector like the Explore Scientific HRCC to sharpen the edges of the field of view at low magnifications as well.
Being a GoTo scope, the 10” FlexTube needs a power supply. A beefy battery is the most convenient choice; a long cord will wrap around the telescope very quickly.
Lastly, as with almost any telescope, we recommend a good UHC nebula filter, such as the Orion UltraBlock, for improving your views of nebulae with the 10” FlexTube GoTo Dobsonian. The contrast improvement helps to improve your views of nebulae under light-polluted conditions but will enhance the view even under dark skies, and of course dark skies are recommended for viewing any deep-sky object with or without a filter. The 2” filter will screw onto a 1.25” adapter with filter threads like the one mentioned above to be used with either 2” or 1.25” eyepieces.
What can you see?
The 10” FlexTube GoTo Dobsonian of course puts up the bright and bold views of any good 10” Dobsonian under good conditions – provided you get a shroud for the tube, that is. Performance on deep-sky objects is inevitably going to be limited by whatever light pollution conditions you find yourself under – only the darkest skies will allow you to see decent detail in galaxies while severe light pollution will wreck nebulae even with a filter, and obscure globular star clusters too. The same goes for moonlight – if the Moon is more than a thin crescent it’s as bad as the worst city lights. Open star clusters are fairly resilient, however, and those such as the Double Cluster, M35, or M45 are spectacular from almost any sky. Globular star clusters like M13 and M15 can almost always be resolved into individual stars with the 10” FlexTube GoTo Dobsonian at high magnifications and the scope’s GoTo system will find them easily, as well as keep them centered at high power.
While appearing as washed-out smudges to the beginner or under bad conditions, with time and effort you’ll be able to see plenty of detail in galaxies with a 10” Dobsonian under good skies. The 10” FlexTube GoTo Dobsonian will be able to reveal H-II regions and hints of spiral arms in M51 and M33, dust lanes in M82 or M31, and many irregularly shaped galaxies, interacting pairs, and huge groups, including the vast Virgo Cluster containing hundreds of visible members.
Nebulae are also delightful with the 10” FlexTube GoTo Dobsonian. The Orion Nebula (M42), the Lagoon (M8) and the Swan (M17) dazzle even from suburban skies while a UHC filter enhances the view. Dark skies will allow you to see the Veil Nebula supernova remnant with the aid of a UHC filter, along with the Rosette Nebula, the Flame Nebula, and perhaps even the Horsehead. Smaller planetary nebulae like the Cat’s Eye or the Blue Snowball reveal emerald and deep blue colors too, with intricate details visible with high magnification and good seeing. Double stars are also plentiful and many feature contrasting colors, often requiring very steady conditions (and of course good collimation) to split apart at high magnification.
10” of aperture is often considered the “sweet spot” for high-power lunar and planetary viewing before diminishing returns kick in as atmospheric conditions rarely allow the utilization of the full resolving power of much large instruments. The 10” FlexTube GoTo Dobsonian will show you the phases of Mercury and Venus easily, along with dark markings and polar ice caps on Mars under favorable conditions and of course a wealth of fine detail on the Moon which never disappoints. Jupiter’s vivid cloud belts, storms, and of course the Great Red Spot are a delight, and you can watch the four Galilean moons (themselves easily visible in the 9×50 finder) transit and cast inky-black shadows; during transits their disks are more readily apparent and you may be even able to resolve some hints of shading on Ganymede, the largest of the four. Saturn’s rings delight with the Cassini Division visible within; when the rings are at a wider tilt (not until after 2030) you may also be able to make out the Encke gap in the rings too. Saturn shows cloud bands like Jupiter’s but they are dull, uniform and less distinct, while a half dozen moons can be seen next to it as star-like points, the brightest being gold-colored Titan, which is vaguely apparent as not-quite-a-star on account of its angular size, just barely resolved with the 10” FlexTube under very steady conditions. You can also tell that the asteroid Vesta is out of round under similar conditions at very high magnfications; it is around the same angular size and color as Titan.
Uranus’ teal-green disk is resolved with the 10” FlexTube GoTo Dobsonian with possible hints of cloud detail, while up to 4 of its moons might be visible if you can spot them amid its glare; our guide on observing Uranus goes into more detail. Neptune is often just a bluish fuzz but its moon Triton is fairly obvious next to it, while Pluto is just barely within the grasp of the 10” FlexTube GoTo Dobsonian’s light-gathering power under dark skies as it continues to grow dim; the dwarf planet is still visible as a star-like point if you know where you are looking.
Astrophotography
The 10” FlexTube GoTo Dobsonian’s fairly large aperture and motorized tracking capabilities make it an excellent choice for planetary astrophotography. It is on par in performance with many of the popular catadioptric telescopes among lunar and planetary imagers. To get the sharpest possible images, a color high-speed CMOS camera like the ZWO ASI224MC in combination with a 5x Barlow lens is ideal; with just a few minutes of footage, amazing shots can be achieved of the Moon and planets. Deep-sky astrophotography is not viable with an alt-azimuth mounted, unguided telescope such as the 10” FlexTube however.
