The Optical Tube Performance Of Skywatcher 6″ Dob
The Skywatcher Classic 150 Dobsonian uses basically the same optical tube as the Orion XT6. It’s a 6” f/8 Newtonian – a design fairly easy to manufacture to tight tolerances. The f/8 focal ratio also makes the scope perform well even with cheap eyepieces such as the scope’s included “Supers” (which will suffer from astigmatism and other aberrations in faster scopes), and the 48” (1200mm) focal length puts the eyepiece at an ideal height for children or seated adults. The tube will fit across the back seat of most vehicles, though probably not in the trunk/boot of a smaller car.
The 6” Traditional uses a single-speed 2” rack-and-pinion focuser, which largely consists of metal – unlike the 1.25” plastic rack-and-pinions found on almost all cheaper scopes. This focuser works quite well for visual use but the adapter system Sky-Watcher includes is a little confusing, requiring you to swap out 2” and 1.25” extension tube adapters depending on which size eyepiece/accessory you are using. You can get a 2” to 1.25” compression ring adapter and leave the 2” extension tube in all the time to solve this, however. The 2” eyepiece format allows you to get a wider field of view than possible with 1.25” eyepieces at low magnifications, making it easier to find targets and fit larger ones in one field. However, with the widest-field 2” eyepieces there may be some vignetting due to the rather small secondary mirror in the scope, which is inadequate to fully illuminate the field of view of all 2” eyepieces.
Reviewing The Accessories
In addition to its ubiquitous 1.25” and 2” extension adapters, the 6” Traditional includes two 1.25” “Super” eyepieces which seem similar to Plossls – a 25mm (48x) and 10mm (120x). These eyepieces will serve you well to start but we’d recommend picking up additional eyepieces down the road if your budget suits them, to get the most out of the scope.
The included finderscope is a rather basic 6×30 unit, which works just fine, but the aperture is a little small, the images are dim as a result, and the ergonomics are less than ideal.
About the Mount
The 6” Traditional uses the same mount design as the larger Traditional Dobsonians The altitude motion is provided by two round plastic bearings riding on Teflon cylinders attached to the interior of the mount; tensioning is provided with a spring-loaded knob (basically just a bicycle handle and a hardware store spring) on one side; the other knob serves no purpose besides aesthetics/symmetry. Overall the altitude bearing system works well – arguably better than the spring system found on the Orion Dobsonians, though inferior to the GSO/Zhumell bearing style – but the knobs stick out and have an annoying tendency to grab loose clothing or bump into you. The telescope’s azimuth motion is provided by small nylon pads running directly against the melamine coating that covers the entire base, which, while not perfect, is relatively smooth and stable.
Like all commercial Dobsonians nowadays, the entire base is made out of particle board and is easily assembled just like IKEA furniture with an included Allen wrench and screwdriver.
What can you see?
6 inches of aperture is the minimum size widely considered to be suitable for serious viewing of deep-sky objects like the Messiers and many of the NGC objects including the Herschel 400, while still being relatively inexpensive and portable. You’ll be able to resolve the brighter globular clusters such as M13, M15, and M3 into individual stars with no problems.
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The 6” Traditional also makes an ideal lunar, planetary, and double star instrument. You’ll have no trouble seeing the ice caps and dark regions of Mars around opposition, the phases of Venus and Mercury, and thousands of craters on the Moon ranging from just a mile to hundreds of miles across. Jupiter’s moons, cloud belts, polar zones, festoons, and its (slowly-shrinking) Great Red Spot are visible. Saturn’s rings, the Cassini division within them, some weakly-visible cloud banding, and around half a dozen moons can be spotted. Uranus and Neptune are teal and azure dots, and you may just be able to spot Neptune’s moon Triton with dark and steady skies. The 6” Traditional can also split double stars as close together as 0.75 arc seconds apart, and will reveal thousands of asteroids to the keen-eyed observer (though keep in mind that none will look like anything more than slow-moving, stellar dots).
For similar prices to the 6” Traditional, there are a number of other scopes you might want to consider, including the following:
- Orion SkyLine 6 – Slightly improved focuser (albeit 1.25” only)
- Orion StarBlast 6 – Significantly more portable and slightly wider field of view, though requires a tabletop.
- Celestron Astro-Fi 130 – Slightly smaller aperture, but full GoTo and can be controlled via your smart device.
Aftermarket Accessory Recommendations
The #1 accessories we’d recommend for the 6” Traditional are extra eyepieces. Specifically, a 2” wide-angle eyepiece such as the GSO 42mm SuperView, and a high-power eyepiece such as a 6mm goldline or a 5.5mm Meade UWA. The wide-angle 2” eyepiece will make it easier to find objects and provides a sweeping vista that’s great for the largest star clusters and nebulae, while either of the latter eyepieces will provide great close-up, high-magnification views of the Moon, planets, double stars, and globular star clusters.