Sky-Watcher’s 8” Traditional is one of my favorite 8” Dobsonians that I recommend to those on a budget. Why, you might ask? It’s simple, offers the lowest price of all of the commercially-available 8” Dobsonians, and gives you good bang for your buck. Let’s go into what makes this scope so great, as well as a few of my criticisms.
The Optical Tube
The 8” Traditional is an 8” f/5.9 Newtonian, manufactured by Suzhou Synta Optical Technologies – the same company that owns Celestron and manufacturers Orion’s XT and XX Dobsonians. The mirrors are borosilicate glass (Pyrex) which expands far less with expansion and contraction than plate glass. Quality-wise they tend to be good
At f/5.9 there isn’t any coma like there is with faster scopes such as Sky-Watcher’s 10” and larger models, which have to have faster focal ratios to avoid being cumbersome and (at the largest sizes) requiring a tall ladder.
The 8” Traditional’s tube is identical in length to Sky-Watcher and other manufacturers’ 6” f/8 Dobsonians, and as a result it is not really any more cumbersome to transport or more difficult to store.
The focuser on the 8” Traditional is a rack-and-pinion. It works just as well as a Crayford unit, but there are two issues I have with it: First, the knobs are hard plastic with little ridges that dig into your fingers. Second, the focuser comes with a strange thread-on 1.25” adapter and a thread-on 2” adapter, which means that unless you spend additional money on a separate 1.25” to 2” adapter you’ll be fumbling around in the dark with these silly adapters. I don’t get why Sky-Watcher elected to add this system rather than just supplying the 2” adapter and a 1.25” to 2” adapter.
The 8” Traditional comes a 25mm (48x) and 10mm (120x) “Super” eyepieces that seem to be Plossls. They work well, but you’ll want some additional 6mm and 9mm “gold-line” eyepieces at the minimum for high power (the 10mm Super is a little short on eye relief), and a 2” wide-angle eyepiece to get the maximum possible field of view at low power for expansive views of nebulae, star clusters, and other deep-sky objects.
The 8” Traditional comes with a 9x50mm straight-through finderscope. In addition to being uncomfortable to aim through at almost every angle, the finder’s images are inverted. A Telrad is far easier to use, and a 50mm right-angle finder will also work well and do wonders for your neck.
The Dobsonian Mount
Like all other Chinese-made Dobsonians, the 8” Traditional’s mount is made of melamine-covered particle board – basically, sawdust compressed with glue, and a cheaper version of the stuff your IKEA furniture is sometimes made out of. It’s heavy compared to plywood, and if the melamine is damaged even slight moisture (i.e. being used in the grass) will warp it.
Unlike Orion’s XT Dobsonians which use springs for altitude tensioning and have the altitude bearings sit in cutouts in the mount, the Sky-Watcher Traditional Dobsonians have the altitude bearings sit on brackets inside the rocker sides. This makes replacing it with a plywood rocker more complicated if you aren’t an experienced woodworker.
Altitude tensioning is provided by two handles which stick out from the rocker (basically bicycle grips). This system works well but the handles can get caught on things such as loose clothing, especially in the dark.
The scope’s motions are pretty smooth, but the azimuth motion can be improved by replacing the cheap Nylon pads with real Teflon pads (available from various vendors on eBay and some hardware stores) and nailing a sheet of Formica onto the azimuth board. Due to the design of the altitude bearings, I would not recommend tampering with them.
The mount comes with a handle and an eyepiece tray – nice conveniences, but I don’t recommend using the ladder as it’s a good way to get your eyepieces damaged, dewed up, or dirty.
In The Field
An 8” Dob is the largest size at which I really like solid tubes. A 10” scope becomes a bit uncomfortable to wrap your arms around and a 12” or larger is plain nightmarish to handle unless you are built like Paul Bunyan.
The Moon looks good in any scope, but an 8” is a good general size for lunar viewing – you have a decent resolution but the Moon isn’t blinding at sane magnifications. Clavius can show three or four dozen craterlets provided good seeing and collimation.
Jupiter’s moons are nice disks with an 8” and show some amount of color, particularly Io, which is a ruddy orange-yellow. Galileo Regio on Ganymede can be hypothetically glimpsed with an 8” but I’ve never done it. Jupiter itself shows many festoons, cloud belts, and of course the Great Red Spot.
Saturn shows several bands – currently it has three major ones – as well as the Cassini Division in its rings, and several moons. Saturn’s largest moon Titan is a gold color, but it falls short of being a disk with anything less than perfect seeing conditions.
Uranus’ moons can hypothetically be glimpsed with an 8”, but I’ve never done it in practice. Neptune is a nice azure disk and Triton can be seen with some effort.
Outside the solar system, 8” of the aperture is enough to show you the entire Messier catalog, though a few galaxies like M74 and M83 may be difficult if you suffer from light pollution. The famous Whirlpool Galaxy can just show a hint of spiral arms from a dark site, and its companion M51B/NGC 5195 is pretty easy to see. M81 and M82 in Ursa Major are quite interesting. In the spring, the Virgo Cluster becomes a bit crowded with galaxies, and in the autumn several smaller galaxy clusters may show at least one or two bright members with effort.
Globular star clusters with an 8” actually start to show resolution. M2, M3, M5, M13, M15, and M92, in particular, tend to show a fair amount of stars sprinkled across with an 8”, while M4 may yield fantastic views if you don’t live too far north and don’t have much light pollution to the south of you. Even the dimmer Messier globulars like M10, M12, and M79 can show hints of resolution with practice.
Many planetary nebulae besides the Ring and Dumbbell are interesting to investigate with an 8” (particularly with light pollution or oxygen-III filter), such as NGC 1535 in Eridanus and the Eskimo Nebula in Gemini in the winter, and the Blinking Planetary nebula and NGC 7027 in Cygnus in the summer.
While there are one or two 8” Dobsonians with extra accouterments that I might recommend over the Sky-Watcher 8” Traditional, none deliver the same value and low price. If you’re on a budget and would rather save additional spending on accessories for later, the Sky-Watcher 8” Traditional is your friend.