Light Bucket: The Sky-Watcher 10-inch Collapsible Dobsonian

My first real telescope was an Odyssey 8-inch Dobsonian purchased in 1987. This scope revealed the deep sky universe to me, and I used it for many years until I became interested in other kinds of telescopes. I ended up selling the Odyssey to purchase my first refractor, a TeleVue Pronto. I fell in love with the sharp, pinpoint stars and wide field views of a small refractor, yet I knew that I would eventually get another light bucket for deep sky observing.

I just obtained a Sky-Watcher 10-inch collapsible Dobsonian. With the recent rebates and free shipping offered the dealer I chose, I felt that these scopes were a great value. I paid $495 total for a 10-inch scope.

When I first saw these scopes advertised, I was skeptical about the retractable design. I felt that the collapsible tube would be wobbly and not hold collimation, yet I decided to go ahead and order a Sky-Watcher 10-inch Dobsonian after reading many favorable reviews. I was especially impressed with the May 2009 Sky & Telescope review of the 12-inch model. I thought that the collapsible tube system would facilitate the scope’s ease of transport and setup. I also like that the scope broke down into only two pieces and that the tube didn’t need to be taken apart like other truss scopes.

I had to wait for nearly a week. The scope arrived in two boxes: The complete OTA was packed in one box, the disassembled base in another. I put the base together in one evening, and it was a very simple and straightforward process.

Besides the three truss assemblies, the Sky-Watcher 10 features a four vane spider, a large Crayford focuser, twin navigation knobs on the upper assembly, twin altitude handles that serve as balance aids, and a metal mirror cell featuring three collimation and locking knobs. The black, gold-flecked tube is accented with white, crinkle-painted fixtures. When set up, it’s a very attractive looking instrument.

The scope package includes a right-angle 8x50 finder, 25mm and 10 mm plossl eyepieces, 1.25 and 2 inch adapters for the focuser, dust covers for upper and lower tube assemblies, and various tools for assembly.

Note the focuser, a navigation knob, two dust covers, azimuth tension knob (right side of image) and an extra Telrad

The Sky-Watcher 10’s optics consist of a 254mm parabolic mirror and a 58mm secondary. With a focal length of 1200mm, this yields an f/4.7 instrument.

This image shows part of the mirror: Note the collimation donut and mirror clips (there are six clips total)

The scope needed collimation. I tweaked the secondary mirror using an included Allen wrench. Luckily, I had saved a Tectron Cheshire eyepiece from my earlier Dobsonian days, and I was able to get the scope precisely collimated. The primary mirror was center-marked with a white donut sticker to aid alignment.

SW10 Mirror Cell: Note collimation and locking knobs, four holes for a fan installation

Initial observations, made that same evening, looked very good. I was also able to observe the waning gibbous moon through a break in the clouds right after putting the scope together. Despite a warm mirror, the image was pleasing, and a quick star test revealed no significant issues with scope’s mirror.

A couple nights later, I allowed the scope to cool down for a couple hours before observing. I had a lot of fun observing various deep sky objects (Double Cluster, M2, Saturn Nebula, M77). The scope took me back to my early observing days with the 8-inch Odyssey. The Sky-Watcher-10 isn’t that much larger than the Odyssey. I also liked that I could observe in a seated position using a Denver chair even when the scope was pointed straight up. Like Goldilocks, it seemed just the right size for me.

I used Polaris and was able to get a good look at the mirror’s star test. Inside and outside, the images were round, no astigmatism or pinched objects were seen. I did observe a slight bit of overcorrection. This doesn’t seem to matter in the final images, which are very good.

I have had other clear nights and memorable observations with the Sky-Watcher 10. My observing site, a small town between Chicago and South Bend, Indiana, has an “orange” rating on light pollution maps.

Galaxy M74 appeared as a faint, mottled disk with a bright center-rather like a smaller version of galaxy M33. M33 itself was a faint, hazy, mottled disk of light, and I could discern the lazy, S-shaped spiral pattern and the bright patch of NGC 604. With M31, I could see the edge of the galaxy’s dust lane against its bright core. With the extra aperture provided by the Sky-Watcher 10, M31’s companion galaxies M32 and M110 became interesting objects in their own right. I also saw galaxy NGC 891 as a faint, cigar-shaped glowing cloud located NE of double star Gamma Andromedae. Galaxy NGC 404 was easily spotted in proximity to the bright star Mirach in Andromeda. Low in the southern sky, Edge-on galaxy NGC 253 was easy to see and resembled a faint glowing cloud. Planetary nebula M76 appeared twin-lobed with one end conspicuously brighter than the other. M1, the Crab Nebula resembled a misshapen patch of light suspended against a starry background-at times I could detect hints of the Crab’s legs. Globular clusters M15 and M2 were recognizable as immense congeries of countless stars. Each globular had a distinct appearance-M2 in particular resemble a faint pile of sand that radiated tendrils of stars in many directions.

On a clear weekend night, I waited for Orion to clear the trees on the east side of my backyard. Realizing that each view of M42, the Orion Nebula, seems like the best one ever, I was still very excited and amazed at the nebula’s appearance in the 10-inch scope. The nebula’s outré, greenish witch-light was flecked with undulations and surrounded by faint wisps of nebulosity. The central square-like bright portion surrounding the Trapezium was mottled and possessed the famous “mackerel sky” appearance. I could easily spot the extra two stars E and F in the Trapezium. The wing-like appendages of the nebula spread out like an immense eldritch bird in flight- the extra aperture really makes these portions come alive. I was also struck by how dark the segment of sky between M42 and M43 appeared. This is an area of dark nebulosity superimposed in front of the glowing nebulae, and it looked like a black wave just starting to break into the nebula.

As you can tell, I have been very happy with the scope’s deep sky performance. The images are outstanding. I haven’t been able to obtain decent planetary images from the Sky-Watcher 10. Either the seeing or a warm mirror has interfered with the views. I think that it will perform well in this capacity when seeing conditions permit.

As I was writing this review, I had another opportunity to observe the moon. The scope was fairly well cooled, and the waxing gibbous moon exploded with detail. Crisp features of craters, mountains, and mare were evident when waves of seeing permitted. I also binoviewed the moon using a Denkmeier Big Easy binoviewer, and this setup worked very well with the Sky-Watcher 10.

Since deep sky observing was out this evening due to the waxing moon, I observed a few double stars. I was able to obtain good splits of Polaris (mags 2.1, 9.0; sep 9”), Theta Aurigae (2.7, 7.2; 4”), Gamma Ceti (3.6, 6.2, 3”), and Alpha Piscium (4.1, 5.2; 1.9”).

With the Sky-Watcher 10, I used a 31mm Nagler, 24mm Panoptic, 13mm Nagler, 9mm Nagler, and 7mm Nagler for my observations. I found the 13mm to be the best overall eyepiece, and the Naglers dealt well with any coma generated by the scope’s fast optics (somewhat less with the 24 Panoptic). With the heavy 31 Nagler, I needed to tighten the scopes altitude handle substantially to keep the scope from sinking. The smaller eyepieces mentioned above were very ideal for this telescope and created no balance issues. I didn’t use the included 25mm and 10mm plossls, yet they appear to be decent entry-level eyepieces.

SW10 Eyepiece Chart

I really like the Crayford focuser. It is extremely smooth, and it is very easy to make fine focus adjustments. It has no trouble handling large heavy eyepieces like the 31mm Nagler or a binoviewer. The focuser utilizes 1.25-inch and 2-inch adapters, which are attached with setscrews. The adapters both employ setscrews to hold an eyepiece. Brass compression fixtures would have been nice, but it’s not a big deal. I eventually started using the Sky-Watcher 2-inch adapter combined with a TeleVue 1.25-inch adapter.

SW10 Focuser: Two-Inch Adapter with TeleVue Adapter and 13mm Nagler Eyepiece

To find objects, I replaced the right-angle finder that came with the Sky-Watcher 10 with a Telrad. I am a Telrad fan, and I think that it is the best finder available. The Sky-Watcher right-angle finder was an absolute pain to use, and I found it completely non-intuitive-I need to look up parallel to a scope to point it.

I have repeatedly collapsed the scope and checked its alignment with the Cheshire eyepiece, and the scope holds collimation pretty well. I do find it necessary to tighten the truss bolts in the same sequence (starting with the top truss and moving counterclockwise) each time to maintain collimation. I have had to tweak the collimation occasionally, but it will easily hold for an evening of observing. I leave the Cheshire eyepiece in the finder as a lens cap and check the scope’s collimation each time before use. The mirror cell itself is nicely made and features three collimation bolts and locking screws. It is easy to adjust and check the scope’s collimation from a seated position.

One of the SW10’s attachment mechanisms, note the chrome knob used to tighten the truss assembly

The collapsible tube design is a really elegant feature. It makes the scope much more manageable to set up. I usually take the tube out of the rocker box when moving the scope. When disassembled, the collapsed tube is much easier to carry through a doorway, and I don’t worry as much about banging the scope into any doorjambs. I can lift the scope with the two altitude handles if I wish (the entire scope weighs 59 pounds, I checked using a bathroom scale). The handle hardware is robust and will easily support the weight of the scope. (Here is a YouTube video of the Sky-Watcher 10 in action).

The SW10 Collapsed

The SW10 is easy to transport

The scope addresses balance issues by the use of two threaded handles that bolt into the azimuth bearings of the tube. Tightening these handles causes the rocker box to flex slightly inward compressing the tube. This system works well, and as I mentioned the handles can be used to carry the entire scope. Yet I think that the greatest advantage of these handles is that they provide a decent amount of leverage when moving the scope pointed near the zenith-aka Dobson’s Hole. This really is a big improvement over trying to move the nearly vertical scope by grasping the side of the rocker box.

SW10 Azimuth Tension Handle

Other than adding a Telrad, I have found that the Sky-Watcher 10 works as advertised and needs no modifications. The telescope’s motions are smooth and stable. The metal tube does vibrate a bit in comparison to a cardboard sonotube scope like my previous Odyssey 8. Despite this, one can easily point and drive the scope by hand. The altitude and azimuth motions are very similar, and this happy state allows one to drive the scope smoothly without a series of step-like jerks. I am happy that the 10-inch uses Teflon pads as azimuth bearings instead of the lazy susan bearing used in the 12-inch. The Teflon pads are very smooth. The altitude bearings ride on fixed vinyl cylinders. This is a decent setup that creates just the right amount of “stiction” for smooth altitude motion.

SW10 Side Bearings

As I said above, the Sky-Watcher 10 can be used as is without modification. Yet there is something about a Dobsonian telescope that inspires one to tinker and experiment. I have performed some slight modifications.

I replaced the central azimuth bolt with a Krieg-style plate consisting of an all-metal lock nut welded to a flat steel plate. This setup keeps the azimuth bolt completely vertical and eliminates some slop from the scope’s azimuth motion. It wasn’t really necessary to do this, but I had the Krieg plate from a previous telescope project and it does make a small improvement.

Bottom board of SW10 showing Krieg-style plate

I also had a cooling fan left over from the same telescope project. I use three plastic hooks (3M Command), the kind that affix with tape and are removable, as anchors for the fan. I had attached the fan to a round thin board with dowel feet. The fan helps to cool the mirror faster, and the round board forces air around the mirror and into the tube. The fan vibrates too much for observing, but I can attach it for a while to cool the mirror and then easily remove it before observing. I used three of my daughter’s elastic hair bands as holders.

Homemade Removable Cooling Fan

Another concern I had was that the scope’s range of motion allowed the ends of the truss tubes to strike the inside of the rocker box when the tube was oriented vertically. To prevent this, I inserted a plastic, felt covered bumper in one of the holes for the rocker box’s front handle. (The insert was the head of a plastic bolt used for installing vinyl shutters.) This installation keeps the tubes safe from impact. I’m surprised that Sky-Watcher didn’t include some type of bumper for the scope.

Bumper and Felt Pad placed into top threaded insert

My only major concern about the Sky-Watcher 10’s construction is how the secondary mirror is attached to the spider. It appears to be held on by double-sided tape. I worry that the mirror will eventually fall off. I am thinking of installing some type of safeguard for this. I have also considered obtaining a curved-vane spider from ScopeStuff. Despite this, the spider diffraction effects are pretty muted in this scope and have not been obtrusive when observing.

SW10 Spider & Secondary Mirror

Concerning the Sky-Watcher 10’s overall quality and construction, I am really impressed with what you can get for a few hundred dollars. The fit and finish of the scope is terrific. The focuser, spider, mirror cell, and collapsible trusses are very well made. The white fixtures feature a crinkle style paint job that appears very durable and attractive. I also like the black paint with gold-flecked highlights. It is a subtle bit of bling that contributes a lot to the good looks of the scope.

Blingin’

In summary, I absolutely recommend the Sky-Watcher 10-inch Collapsible Dobsonian. I believe that Sky-Watcher’s effort to create a new type of collapsible tube was a success. The design was well thought-out and executed, it works very well, and the collapsed tube is much easier to carry. The images delivered by the scope are outstanding when used with modern eyepieces. This is the largest aperture scope that I have ever owned, and the difference in light gathering ability is quite a contrast to my refracting telescopes.

My Goldilocks Scope