Explore Scientific - Generation II - 20-Inch Truss Tube Dobsonian Telescope
The ideal workhorse for the deep sky observers, the Explore Scientific 20-inch f/3.6 Truss-Tube Dobsonian is our largest aperture telescope. The 500mm mirror collects 5100 times more light than the naked eye. Details on planets and deep sky objects will be visible even for inexperienced observers. Bright star clusters are resolved to the core, and the sight of the terminator on the moon is an unforgettable experience.
The fast 20" f3.6 main mirror as well as the large 120mm secondary mirror are made of high quality quartz material, so the cooling time is reduced to a minimum and this Dobsonian is quickly ready for use. Every main mirror is delivered with an individual optical test certificate, which guarantees the highest capacity. A laser engraved center mark of the main mirror allows easy adjustment. The optical surface has a high-quality aluminum coating with 94% reflectivity and an extremely resistant quartz protection layer. The mirror overcomes frequently occurring dew fogging and cleanups without damage and guarantees a long service life.
No telescope type has changed the hobby quite as much as the Dobsonian. Before the introduction of the Dobsonian by John Dobson, the vast majority of amateur telescopes consisted of small telescopes with primitive mechanics - barely enough to see the polar caps of Mars or the rings of Saturn. Larger telescopes, such as the Schmidt-Cassegrain were reserved for the wealthy. The ingenious combination of simple yet effective mechanisms with the greatest possible opening gives the Dobsonian telescope a unique triumphant march around the world. Nowhere do you get as much light for your money like a good Dobson. Disassembly of the scope without tools ensures a trouble-free transport of this great scope even in small cars. The entire structure has been optimized for maximum stiffness with minimal weight. The combination of high altitude bearings with optimized aluminum structures allows fine adjustment flows at high magnifications.
A complete redesign of this Dobsonian was necessary to ensure the significantly increased requirements to stiffness and load bearing capacity of the optical components. All connections of the tube structure were made in the TIG welding process and no rivets and screws were used. This has made it possible for us to produce this 20" light weight Dobsonian so unbelievably stiff in spite of the low weight - a noticeably good quality which is begging you to take one home. The production of almost all mechanical components is carried out by our partners in Hungary and the final assembly of the optics and subsequent quality control takes place in Rhede, Germany.
A second 40° displaced installed mounting plate with a viewfinder shoe allows the rotation of the tube top in combination for a favorable position of the viewfinder tube or the mounting of an additional TELRAD viewfinder. The 6 supporting feet underneath the rocker box offers perfect stability and guarantees smooth tracking in azimuth. Four smaller fans are installed in the side of the mirror box as well as a large fan installed under the main mirror. This allows an even quicker adaptation to the ambient temperature and reduces the tube seeing (boundary layer removal). The lateral altitude wheels can now be stowed comfortably in the foam layers of the mirror box.
Includes 2.5" HEX focuser with helical gearing and 10:1 reduction; LED Red Dot Finder, collimation assist tool; soft light baffle and two radial main mirror fans for fast temperature equilibrium.
The scope is ready for the use with our optional coma corrector.
|Focal length||1,826 mm|
|Primary mirror diameter||50 cm|
|Mirror cell support points||18|
|Truss pole length||100 cm|
|Truss pole diameter||25 mm|
|Secondary cage assembly diameter||57 cm|
|Secondary cage assembly weight||8 pounds|
|Secondary cage assembly height||95 cm|
|Mirror box/rocker box height||56 cm|
|Mirror box weight *||105 pounds|
|Height to center of eyepiece at zenith||170 cm|
|Theoretical limiting stellar magnitude||0.23 arc sec|
|Theoretical Rayleigh limit||0.23 arc sec|
|Theoretical limiting magnitude||16.19 mag|
|Theoretical maximum magnification||1,000x|
|*||Mirror weight can vary because of the manufacturing process; these values are approximate|
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