Sky-Watcher Dobsonian Series
John Dobson, of San Francisco Sidewalk Astronomer's fame, is credited with popularizing the large aperture, low cost, light-bucket concept. The Dobsonian is a fast focal ratio (large aperture, short focal length) Newtonian reflector placed on a rudimentary, but functional altazimuth rocker mount. The basic, bare bones Dobsonian concept of 6-and 8-inch telescopes for the masses was wildly popular in the 1980's and ‘90's. However, over time the market has since become more discerning and the Dobsonian has evolved accordingly. Thin mirrors known to sag and deform, cardboard tubes subject to warping and moisture retention, and crude slider focusers are largely a thing of the past. Amateur astronomers today still love the big light-bucket concept, but they also want reasonably good optical quality and utility that offers performance staying power over time.
Corresponding to the escalating "aperture fever" that has gripped amateur astronomy for several decades, an 8" aperture is now generally regarded as the minimum entry-level Dobson telescope for serious observing. As such, the fast 8" Dobson Newtonian is the lowest cost, large aperture telescope available to amateur astronomers today. However, the trend in recent years shows the 10" aperture DOB to be inexorably over taking the 8" as the most popular aperture instrument in its class, closely followed in demand for the 12" Dobson.
The demand for affordable large aperture telescopes seems insatiable, except for logistic considerations of transporting increasingly larger optical tubes whose volumes grow dramatically per inch of aperture. Thankfully, a Newtonian optical tube design utilizing truss supports makes it possible to disassemble the front and back cells from the center portion of a Newtonian OTA to dramatically reduce the cube (volume) for easier handling and transport. Sky-Watcher has an even better answer, an improved truss-support concept that allows the optical tube's front and back cells to collapsible together, aligning on the truss support rods which can then be locked down for secure transport. This one piece, low-hassle OTA design is mechanically simple and results in large aperture telescopes that can be reasonably handled and transported by one individual. This innovation gives Sky-Watcher users tremendous functional ease-of-use.
Observing with the SW Dobsonian
The Sky-Watcher Dobsonian's large aperture and fast focal ratio make it the ideal dedicated telescope for wide-field, deep-space observation of faint galaxies, nebulae, and star clusters. The fast focal ratio dramatically captures wide swaths of sky in a single view. Galaxies and nebula appear to pop out of the heavens as bright, expansive masses of stars, gas, and dust. Our closest external galaxy, the beautiful Andromeda, can essentially be seen almost in its entirety within one eyepiece field, a feat that is virtually impossible with longer focal length instruments. Andromeda is perhaps the defining galaxy of the classic spiral form. The low operating power of SW Dobson models allows deep-space gems to leisurely drift through the field of view over several minutes without the need to mechanically readjust the telescope's physical orientation to the sky. In contrast, longer focal length optical systems can require adjustments in less than a minute to keep objects within the field of view (unless the telescope has a motorized clock-drive).
Observing with a Dobsonian has been described akin to shooting ducks in a gallery because it is so easy to find your target. Just swing your SW DOB to the quadrant of sky to be searched, and scan the vicinity. To ensure ease-of-use, SW uses a high-performance Teflon bearing system in both axes combined with tension adjusters in altitude that facilitate setting the appropriate amount of friction or stricture to assure smooth manual movement without free-play from small bumps or gusts of wind. This also eliminates the need to have a balanced optical tube as in an equatorial mount. The Teflon bearing system is preferable to the use of ball-bearings. Ball-bearings make unintended optical tube movement more difficult to control.
Sky-Watcher Dobsonian telescopes offer quality optics, huge aperture, solid construction, and superb value for the investment. If you are looking for a big light-bucket, look no further! Sky-Watcher has what you need!