20-inch Aperture Telescope

20-inch Aperture Telescope


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20″ f/4.0 Truss Tube Dobsonian Telescope

Own the biggest amateur telescope there is in India! The 20-inch Aperture Telescope (500mm) collects 11 times the light as compared to a 6-inch newtonian. The telescope performs exceptionally well. Faint Deep Sky objects will look like photographs, you won’t ever feel the need to do deep sky astrophotography. The 20-inch will perform nicely even if the sky transparency is not so good. You can transport the 20-inch to high altitudes, dark skies; the view will be etched in your mind for a lifetime.

Bye-bye astrophotography, you will be amazed by the views from this telescope.

Bigger is certainly better, with telescopes. The light collection increase is directly proportional to area of the primary mirror, i.e. the square of the radius of the telescope.  Even small increase in diameter can be significant increase in brightness and resolution. With a massive 20-inch aperture you can collect a humongous amount of light from the faint deep sky objects. This is the largest telescope, available on the consumer market in India.

The telescope is portable, can be separated into three parts, the lower tube assembly, upper tube assembly and the truss tubes. Assembly of the telescope can be completed in 5-10 minutes on site. No tools are required for assembly.

The optics of a Dobsonian Telescope are of the Newtonian reflecting type. Dobsonian Telescopes do not suffer from chromatic aberration as in refracting telescopes.

Dobsonian Telescopes are perfect for beginners and amateur astronomers. It can be setup quickly and up and running in just a few minutes. Just point and take a look. Dobsonians are the simplest design for a telescope.

Views through this giant Dobsonian are always incredible. You need a ladder to look through the eyepiece when it is pointing at most targets overhead.

Planet Observations: The telescope shows great views of the planets, you can see the surface features clearly. The resolution of a telescope is a function of its diameter. A 20 inch telescope can resolve much more details on the surface of planets. Along with the resolution, since there is good amount of light collected, you can see surface features on planets in high contrast. This is the benefit of using a large telescope

Deep Sky Objects: When you look at deep sky objects such as globular clusters, the naked eye view is far superior to photographing it. It is impossible to photograph the beauty of the intensely dense group of stars in a globular cluster. Take for example of Messier-3 (M3). Or Messier-13 (M13), the Great Hercules cluster, the real-time view is much better using the 20-inch. You can see deeper, many more stars, all sharply focused and separate till the core.

When you look at the Ring Nebula you can see the smoke ring bright and even discern the onion like extensions on two sides of the ring. The colours of double stars such as Albeiro are spectacular. You can also discern the colours of the stars more easily in the Aperture Telescope 20-inch telescope.

Bye-bye astrophotography

Our 20-inch telescope is a Truss Tube Telescope. A truss is an assembly of straight columns that create a rigid structure. The columns of a truss are organized so that the assemblage as a whole behaves as a single object. A truss is made up of a web of triangles joined together to enable the even distribution of weight and the handling of changing tension and compression without bending or shearing.

Truss Tubes are used on our larger telescopes as there are advantages to using the truss set up. Truss tubes makes a very strong optical tube with little or no vibrational motion or slipping. This is important with telescopes because the slightest unwanted motion can ruin the image. Second, the truss set up is very light. Trusses add great strength while drastically reducing weight of the telescope. Trusses also increase portability as they can be dismantled to carry and assembled quickly for observation.


Download Specifications Sheet
  20-inch Truss Tube Dobsonian


Telescope Design Truss Tube Collapsible Dobsonian
Materials used Stainless Steel, Water proof marine ply, Veneer, laminate
Finish Hard PU clear weatherproof paint
Primary Mirror
Mirror maker Hubble Optics, Hong Kong
Mirror physical / optical diameter 518 mm / 508mm
Mirror edge thickness 58 mm
Mirror weight 17 kg
Mirror coating Aluminium + SiO2 Protective coating 92% reflectivity
Focal length / focal ratio 2032 mm, f/4
Mirror Cell 18 point flotation cell
Mirror cell material Stainless Steel (304 grade)
Secondary mirror size 100 mm minor axis
Upper tube assembly (UTA) Dia 595 mm, Height 340 mm, 5.7 kg, covered with light eater black foam
Lower tube assembly (LTA) Height. = 800 mm, Width = 750mm
Dobsonian Mounting
Weight of Rocker box + mirror box 49 kg, weight to be lifted at wheelbarrow handle end – 9.5 kg
Wheelbarrow length 1900 mm
Eyepiece height at zenith 2400 mm
Full height of telescope 2600 mm
Truss tubes length, dia., thickness, weight 1692 mm, 32 mm, 1.3 mm, 5.8 kg, all 8 tubes
Teflon – Side bearing /  Ground board 32 x 32 x 15mm, 4 pieces / 50 x 50 x 5mm, 4 pieces
Side bearing diameter 652 mm
Rocker box wall thickness 38 mm
Wheel barrow additional thickness Add 180 mm both sides, 360 mm
Shroud Opaque two way stretchable lycra
What’s in the box? Telrad Finder,

Crayford Focuser dual speed.

25mm Plössl Eyepiece (1.25″),

Alan key ‘T’ for collimation
Dust covers for primary and secondary mirrors,

Ladder (Bathla)

Wheelbarrow handles



Optional Accessories

Set of five eyepieces, Binoviewer,

Laser collimator,
Complete telescope cover for storage,
Finderscope – refractor type



What’s in the box? Telrad Finder,
Crayford Focuser dual speed,
25mm Plössl Eyepiece (1.25″),
Alan key ‘T’ for collimation
Dust covers for primary and secondary mirrors,
Ladder (Bathla),
Wheelbarrow handles,


Optional Accessories Eyepieces set of five,
Laser collimator,
Complete telescope cover for storage,

Why Buy Aperture

Why Buy Aperture Telescopes
Top Reasons to purchase Superior Dobsonians from Aperture Telescopes


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