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Back to the Future: The Orion SkyQuest XT6 Dobsonian Reflector

Posted by Michael Aaron McNeely   10/23/2005 12:00AM

Back to the Future: The Orion SkyQuest XT6 Dobsonian Reflector
[ARTICLEIMGR="1"]I am amazed at the equipment available to today’s amateur astronomer. For example, I just purchased an Orion 6-inch Dobsonian, and I can’t help but compare it the first telescope that I owned. The Orion scope represents a significant improvement in quality when compared to a similarly priced 8-inch Dobsonian telescope that I purchased in 1987.

I got into astronomy in the mid-1980’s, and my first telescope was an Odyssey-8, an 8-inch Dobsonian reflector. The Odyssey-8 tube assembly consisted of a cardboard Sonotube, and the base was a heavy box constructed of chipboard. The focuser was made of plumbing fixtures. You focused the scope by sliding a drawtube within a plastic ring and, when proper focus was achieved, you tightened the ring. The mirror cell consisted of two particleboard disks, and the mirror was connected with duct-tape and a metallic pipe clamp. The scope was collimated using six push-pull bolts. The scope’s “spider” consisted of a vertical steel bar with a smaller angled piece to which the mirror was adhered with a pad of sticky, foam tape. The secondary mirror fell off eventually. There were no adjustment screws on the spider, and adjusting the secondary mirror required a form of dead reckoning along with a prayer for success. Since the scope didn’t include a dust cover, I employed an elastic shower cap.

The scope had no finder, so I ordered a Telrad. According to the directions, you were supposed to tie the base of the Telrad to the scope’s tube with two heavy strings. As you can imagine, this didn’t work at all, and I decided to attach the base by screwing it to the cardboard tube.

The scope came with an eyepiece, a recycled zoom affair that probably came from a pair of binoculars. My particular eyepiece never properly focused.

Being an f/4.5 scope, I never used it much for planetary observing. Back then, my main interest was deep sky observing. The mirror provided good low-power views. It was fun to sweep the heavens with a 32mm Konig eyepiece that delivered about a 1.5-degree field. I purchased a nice Cheshire eyepiece and applied a central spot for collimation. Eventually I employed a laser collimator.

Despite its lackluster construction, I loved the scope and it provided my first serious foray into the study of the heavens. The Odyssey-8 was smooth and stable. I was able to locate faint deep sky objects from my semi-rural, central-Indiana home.

I used the Odyssey-8 off-and-on for many years. Eventually, after discovering Astromart, I sold it, and used the cash to buy other astronomy equipment. I have since owned various scopes including an old orange-tube Celestron-8. I currently own a Meade 7-inch Maksutov and a TeleVue Pronto.

As a high school earth science teacher, I wanted a dedicated telescope to use with my students. Last summer, I acquired some grant money from the University of Notre Dame, and I used it to purchase an Orion Telescopes SkyQuest XT6 Dobsonian. I was attracted to this scope because of its long focal length and bargain price. I also felt that the XT6 would be a good example of an entry-level telescope for my students.

The scope was delivered in two boxes, one for the base and one for the tube. All of the components were well packed and arrived in good shape.

The tube is made of steel, and it includes a hard plastic dust cover, a four-vein spider, 6x30mm finder scope, and a 1.25-inch metal rack-and-pinion focuser. The scope’s 6-inch, f/8 mirror is held by four plastic clips in a metal mirror cell. The cell features three large collimation bolts for tool-free adjustment. Unlike my old Odyssey, the back of the mirror cell is open, which facilitates cooling of the scope’s optics.

The base is constructed of black laminated particleboard, and it arrived disassembled in a flat box. The particleboard is dense and provides a heavy, solid base for the scope. The components were cut precisely for a tight fit, and the base went together easily and securely with the included hardware.

One feature unique to the XT6 is the “CorrecTension” spring system. The springs hold the tube to the base and provide extra friction to correct for balance problems (this particular model of the XT series is nearly balanced anyway). They provide an elegant solution for balancing the scope. In contrast, I needed to attach weights to the back of the Odyssey-8 to offset the imbalance create by the use of heavy, front-end components. The springs also hold the tube and base together to form a single unit for convenient transportation.

Other unique features of the XT6 are the navigation knob, and metal eyepiece rack The navigation knob is plastic, conic-shaped affair that seems a bit wimpy in comparison to the robust construction of the rest of the telescope’s components. The knob does provide a little extra leverage for slewing with the scope. The eyepiece rack is handy when you don’t want to get up to retrieve a new eyepiece.

A star test revealed a good mirror with nearly identical appearances on either side of focus. The f/8 optics of the scope produce sharp, clear images of stars, planets, and deep sky objects. At the August, 2005 Indiana Family Star Party, I was able to split Antares with the scope. I have done some deep sky observing with the scope, and I find that it provides a substantial jump in performance when compared to a smaller-aperture scope such as my 70mm TeleVue Pronto. Bright globular clusters like M15 are resolved into myriad pinpoint stars. The quality of the images is quite remarkable under good seeing conditions, and the views are not far removed from those in a refractor. My only complaint is that, due to its four-veined spider, the scope displays prominent diffraction spikes when observing bright planets. In this regard, I prefer the views of planets through refractors or Schmidt/Maksutov-Cassegrains.

Collimating the XT6 is very easy, much easier than my old Odyssey-8. The mirror arrived centrally spotted, and the scope came with a collimation cap, which is essentially a small dust cover bearing a sight hole and metallic undercoating. Whoever invented this thing was a genius! The cap makes collimation simple, and it is much easier to use than my Cheshire eyepiece. Despite shipping, the scope arrived in nearly perfect collimation.

The scope includes 25mm and 9mm Sirius plossl eyepieces providing magnifications of 48x and 133x and true fields of 1.0 and 0.4-degrees respectively. These are very nice entry-level eyepieces and are much superior to what was available to beginners in the 1980’s.

In contrast to my experience with the Odyssey-8, one gets the impression of quality and thoughtful design with the Orion SkyQuest XT6. Most of the components possess a nice fit and finish. My only complaints are minor. I didn’t like the plastic knobs on the focuser, and I purchased aluminum replacement knobs from Orion. I also wish that the scope featured a red-dot finder rather than the 6x30 finder scope. I purchased an Orion red-dot finder as a replacement, and it attaches to a stalk that fits in the original finder base.

The only area where the XT6 falls short in comparison to my old Odyssey-8 is in the quality of its Dobsonian motions. The Odyssey was really smooth and stable, and in this regard was well constructed. The XT6 can be a slightly jerky, but not nearly enough to prohibit the use and enjoyment of the scope.

In summary, I am amazed at the wonderful and relatively inexpensive equipment available to today’s amateur astronomers. In 1987, I paid $238 for my Odyssey-8. Today, I paid $249 for a telescope that represents a giant leap in quality over its cardboard predecessor. I can only give this scope an enthusiastic recommendation for beginning astronomers or advanced amateurs wishing a second scope. Its clear, sharp optics provide beautiful views of the heavens. I wish that everyone who purchases a junky telescope from a department store could purchase one of these instead.

Pros:
General metal construction, good fit and finish
Includes eyepieces, finder
Easy collimation
Sharp, clear optics
Open mirror cell
CorrecTension springs hold scope as one unit
Great bargain

Cons:
Plastic navigation and focuser knobs
6x30 instead of red-dot finder
Slightly jerky Dobsonian motion
Diffraction spikes when observing planets

Click here for more about this subject. -Ed.