The Explore Scientific Ultra Light Dobson 20" f/3.6 GENERATION II is the largest of Explore Scientific's Dobsonians - offering enormous light gathering power in a comparatively portable package. If you're looking for a telescope that will actually delivery the types of deep sky views you've been dreaming of without the necessity for permanent observatory mounting - then the Explore Scientific Ultra Light Dobson 20" f/3.6 GENERATION II could be for you.
Despite its large aperture the Explore Scientific Ultra Light Dobson 20" f/3.6 GENERATION II can be transported easily in small cars and is assembled within minutes without tools. The construction was optimized for maximum rigidity with a minimum of mass. The combination of big altitude wheels and an optimized aluminium-sandwich construction allows for small movements even at high magnifications. The focus position is already positioned to accept Explore Scientific's Coma Corrector (part No. 0510330), making it the ideal workhorse for the deep-sky enthusiast. A telescope with a 20-inch/ 500mm aperture gathers more than 5100-times more light than the naked eye. Details on planetary surfaces stand out even to unexperienced observers and countless deep-sky objects show details and traces of color. Bright globular clusters are resolved down to the core and the view of the lunar terminator will provide a unforgettable experience.
Both the fast 20" f3.6 main mirror and the large 120mm secondary mirror are made of high quality quartz material, which means cooling time is reduced to a minimum and the Dobsonian is quickly ready for use. Every main mirror is delivered with an individual optical test certificate, which guarantees the highest quality. A laser engraved center mark of the main mirror allows easy adjustment of collimation. The optical surface has a high-quality aluminum silvering with 94% reflectivity and an extremely resistant quartz protection layer. This overcoat allows the mirror to overcome frequently occurring fogging and dew residue cleanups without any fear of damaging the surface and guarantees a long service life.
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 searching for its match. 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.
The design and equipment specifications of the smaller Dobsonian models, which have not he market for years now, have been used as a basis for this design. First of all, of course, the very easy deconstruction/reconstruction and transportability are paramount. Set-up and dismantling can be carried out without tools. The main and secondary mirrors are adjustable during the observation and only two adjusting screws have to be moved. Thanks to the use of precision ball-heads in the main mirror cell and a precision hinge for secondary mirror suppport, the adjustment is absolutely easy and guarantees excellent stability. All connecting parts of the tube trusses now consist of CNC machined aluminum and are attached by stainless steel dowel screws. The secondary mirror can now also be adjusted by the adjusting screws in the direction of the optical axis. The tried and tested 2.5 "HEXAFOC focuser with 1:10 fine adjustment has been used for years - this allows vignetting-free observation despite the fast aperture ratio. A second 40 ¶ø displaced installed mounting plate with a viewfinder shoe allows the rotation of the tube top in combination with a favorable position of the viewfinder tube or the mounting of an additional TELRAD viewfinder. The 6 supporting feet underneath the rockerbox offer a perfect stability and guarantee a smooth tracking in azimuth. Four smaller fans are installed in the side of the mirror box as well as a large fan is 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.
Last but not least another gimmick: The optical tube and the mirror cell are designed to use also on heavy ÇÏquatorial mounts.
Dimensions for mobile use:
DIMS total: 680x680x1790mm; Rockerbox 678mmx678mmx347mm; Mirrorbox 590mmx590mmx361mm; Trusses approx. 1084mm; Truss diameter: 25mm; Eyepiece height while pointing at zenith approximately 1,63m; 20ƒ__ Total net weight: 53 kg; 20ƒ__ Mirror Box + Altitude wheels: 35,8kg; 20ƒ__ Secondary Cage: 3,8kg; Rockerbox: 10,6 kg; 20ƒ__ 4 Truss pairs: 2,8kg; 20ƒ__ Primary mirror: 20kg
IMPORTANT NOTE: All current product pictures are showing the prototype. Many hints from our customers have pushed us to make some additional changes which will require some updates.
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