Sky-Watcher’s Stargate 18-Inch Dobsonian
By Dennis di Cicco
The Stargate truss-tube Dobsonians are billed as the largest mass-market telescopes available. Is the 18-inch model worthy of the hype?
Stargate 18-inch Dobsonian
U.S. Price: $5,999 ($6,999 as tested with Go To motor drives) skywatcherusa.com
What We Like
Excellent optics
Optional drive offers accurate pointing and tracking
Overall performance
What We Don’t Like
Abysmal instruction manual for telescope assembly
AFTER TESTING SKY-WATCHER’S 18-inch Stargate truss-tube Dobsonian for several months late last year, it’s easy to understand why deep-sky observers proclaim that aperture is king. Objects that appear faint and ill-defined in smaller scopes take on a whole new dimension in an 18-inch. Many globular clusters are transformed from small, fuzzy glows into brilliant spheres of sparkling stars. Lots of planetary nebulae appear large and bright enough to show obvious structure not seen with smaller apertures. And the fields surrounding many familiar deep-sky objects are filled with a multitude of faint background stars lending 3D-like perspectives.
It was apparent how much I liked the Stargate when I quickly found myself looking forward to each clear night as an opportunity to observe rather just one to work on a product review. While the telescope ended up being one I truly enjoyed, and one I can strongly recom-mend, the review process didn’t start out that way. But let’s save that part of the story for later in this review and begin with the good stuff. Although I’m no stranger to using large telescopes, especially at star parties, my own recreational deep-sky observing is usually done with a 12-inch f/5 Dobsonian. As such, the 18-inch Stargate was a signifi cant step up. In addition to having 2¼ times more light grasp than the 12-inch, the Stargate’s longer focal length (1,900 mm versus 1,524 mm) offered notice-ably more magnifi cation for a given set of eyepieces. By itself, this longer focal length would have yielded 25% more magnification. But because the Stargate is an f/4.1 Newtonian and suffers more from coma than the 12-inch f/5, I did most of my Stargate observing with a Tele Vue Paracorr coma corrector that increased the Stargate’s effective focal length by a factor of 1.15×.
And this meant a 43% increase in magnification for the same eyepiece used with the Stargate compared to my 12-inch Dob. The Stargate ships with 2-inch 28-mm and 1¼-inch 10-mm eyepieces of decent quality. They yield 68× with a 49-arc minute field of view and 190× with a 15-arc minute field, respectively. There is also a Cheshire eyepiece collimation tool, which is very good for checking the scope’s optical alignment. Due to the length of the instrument, however, collimating the optics with the included tool is best done with two people — one looking through the Cheshire eyepiece while the other adjusts the collimation screws on the primary-mirror cell. views with a 21-mm Ethos, which gave almost the same fi eld of view as the Panoptic, but at an impressive 103×.
As explained in the accompanying text, the author typically observed with the Tele Vue Paracorr coma corrector pictured here.