Sky-Watcher Stargate 20" f/3.9 Truss-Tube GoTo Dobsonian Telescope

Sky-Watcher Stargate 20" f/3.9 Truss-Tube GoTo Dobsonian Telescope

Sky-Watcher Stargate 20" f/3.9 Truss-Tube GoTo Dobsonian Telescope

B&H # SK20STTGOTOD MFR # S11930
Special Order
Expected availability: 7-14 business days

Product Highlights

  • Large 20" (508mm) Aperture
  • 2000mm Focal Length, f/3.9 Focal Ratio
  • 42,900-Object SynScan GoTo Controller
  • Multiple Alignment Procedures
  • PEC, Backlash Compensation, PAE
  • 2" Two-Speed Crayford-Style Focuser
  • Floor-Standing Motorized Alt-Az Mount
  • 10mm, 28mm, Collimation Eyepieces
  • Large 9x50 Finder with Bracket
  • Easy-to-Manage Open Truss-Tube Design
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Aperture: Stargate 20" f/3.9

18" f/4.2

Special Order

20" f/3.9

Not available with current selections

Stargate 20" f/3.9

Mount: GoTo Alt-Az

Manual Alt-Az

Not available with current selections

GoTo Alt-Az

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Price: $7,999.00

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Sky-Watcher Stargate overview

  • 1Description

With the largest light bucket in the series and the added convenience of a fully motorized GoTo mount, the Sky-Watcher Stargate 20" f/3.9 Truss-Tube GoTo Dobsonian Telescope gives users exceptional performance with a low dollar-to-aperture cost. Proprietary aluminum mirror coatings ensure maximum reflectivity, and a fused conical parabolic primary mirror design allows for thinner mirror construction. This provides faster cooling and lighter weight while also correcting spherical aberration to eliminate distortion across the entire field of view, especially at the edges.

This telescope's large 20" aperture draws in a tremendous amount of light to reveal awe-inspiring details of the Moon and planets. Deep-sky objects will be visible even for inexperienced observers and bright star clusters can be resolved to their core. Its f/3.9 focal ratio and dual-speed Crayford focuser make this an ideal choice for imaging. The fast focal ratio enables devices to capture images in less time than slower scopes, while the focusing mechanism gives it the ability to achieve tack-sharp focusing with zero backlash that rack-and-pinion focusers are generally unable to accomplish. This 2" focuser will accept larger eyepieces so users can enjoy a truly immersive visual experience and will ensure larger imaging sensors are completely covered.

Integrated micro-stepper motors and a worm-wheel/timing belt transmission move the optical tube assembly smoothly without vibrations. Digital encoders on each axis keep track of the mount's position, even when moved manually, to maintain its alignment for easier usability. Controlling the mount is the SynScan computer hand controller. Outfitted with a database of over 42,900 objects including the sun, Moon, planets, galaxies, nebulae, and stars, the controller features multiple alignment procedures to help get users observing faster. A Deep Sky Tour takes users on an automatic tour of the night sky, showing them the best celestial objects overhead on any given day and time. Periodic Error Correction (PEC), Pointing Accuracy Enhancement (PAE), and anti-backlash compensation functions aid the user in correcting the play between gears and the intrinsic errors in the mount and software to improve tracking, slewing, pointing, and GoTo accuracy over time. The intuitive menu-driven system is easy to use by beginners and experienced users alike.

Optical Tube
  • 20" (508mm) aperture
  • f/3.9 focal ratio
  • 2000mm effective focal length
  • Dobsonian reflector light path
  • Fused borosilicate mirror glass allows for thinner mirrors that reduce weight and increase cooling
  • Highly reflective aluminum mirror coatings
  • 134mm secondary mirror, 7% obstruction by area
  • Resolution: 0.28 (Rayleigh); 0.23 (Dawes)
  • Dual-speed Crayford-style focuser enables more precise focusing than conventional rack-and-pinion without backlash
  • Max eyepiece height: 79" (200.7 cm), when OTA is pointed at the zenith
  • Open truss tube design allows for easier breakdown and transportation, with reduced weight versus solid tubes
SynScan Hand Controller
  • Wired hand-held computer controller for mount
  • Intuitive menu-driven system
  • 42,900-object database including 25 user-defined objects
  • Deep-Sky Tour takes user on a tour of the best deep-sky objects visible on any day and time
  • Alignment assistance: One/two/three-star, brightest star, daytime align, polar align
  • Tracking rates: Sidereal, solar, lunar
  • Nine slew speeds: 0.5x, 1x, 8x, 16x, 32x, 64x, 128x, 400x, 600x, 800x (3.4°/sec)
  • Periodic Error Correction (PEC) improves tracking accuracy for long-exposure astrophotography
  • Anti-backlash compensation trains out the inherent play between gears to improve GoTo, slew, and tracking accuracy
  • Pointing Accuracy Enhancement (PAE) allows users to correct pointing accuracy errors for improved GoTo and pointing over time
  • Connect to a computer via user-supplied RS-232 cable
  • Flash upgradable via internet download
  • 2-line, 18-character long LCD variable intensity LCD screen, 19 backlit control keys

Database Details:

  • Solar system including Moon, sun, and planets
  • Named stars
  • NGC catalog
  • IC catalog
  • Messier catalog
  • Caldwell catalog
  • SAO catalog
  • Named stars, double stars, variable stars
Mount
  • Motorized alt-azimuth
  • 0.9°/step hybrid stepper motor
  • Dual-axis digital encoders ensure accurate tracking while allowing mount to be moved manually without compromising alignment
  • Steel and Teflon azimuth and altitude bearings enable smooth movement with limited vibrations
  • Floor standing with adjustable feet for proper leveling
  • Included three 2.3-pound (1kg) counterweights enable precise balancing, especially when using accessories such as heavy eyepieces or imaging rigs
  • Weight: 164 pounds, fully assembled with counterweights
Included Accessories
    Eyepiece:
  • 1.25" 10mm eyepiece yields 200x power, accepts most 1.25" astronomical filters
  • 2" long eye relief 28mm eyepiece produces 71x magnification, accepts most 2" astronomical filters
  • 1.25" collimation eyepiece enables the user to properly collimate the primary and secondary mirrors
  • 2"-to-1.25" reducer adapter allows the use of smaller eyepieces and accessories in the larger drawtube
    Finder:
  • 9x magnification ensures a wide field of view for faster alignment and easier star-hopping navigation
  • Large 50mm objective enables it to resolve dimmer objects
    Shroud:
  • Covers the open portion of the truss assembly
  • Ribbed fabric absorbs internal reflected light
  • Blocks peripheral exterior and reflected interior light which can interfere with light transmission to the mirrors
  • Helps to produce higher contrast views and sharper images during astrophotography
In the Box
Sky-Watcher Stargate 20" f/3.9 Truss-Tube GoTo Dobsonian Telescope
  • SynScan Hand Controller
  • 9x50 Finderscope
  • 2" 28mm Eyepiece
  • 1.25" 10mm Eyepiece
  • 1.25" Collimation Eyepiece
  • Eyepiece Reducer Adapter
  • Ribbed Fabric Shroud
  • 3 x 2.3-lb Counterweights
  • Limited 2-Year Warranty
  • Table of Contents
    • 1Description

    Sky-Watcher Stargate specs

    Optical Design Dobsonian reflector
    Aperture 20.0" / 508.0mm
    Focal Length 2000 mm
    Focal Ratio f/3.94
    Motors Hybrid stepper motor
    0.9°/step
    Eyepiece Barrel Diameter 2"
    1.25" with included adapter
    Diagonal None
    Finderscope 9 x 50
    Tripod None
    Mount Type Motorized alt-az
    Power Requirements 15VDC, 3A
    Optical Tube Dimensions Height: 82.7" / 210.0 cm
    Horizontal radius: 59.1" / 150.0 cm
    Base diameter: 23.2" / 59.0 cm
    Weight Upper Cage: 12.0 lb / 5.7 kg
    Truss Poles: 16.0 lb / 7.3 kg, total; 2.6 lb / 1.2 kg, each
    Mirror Box: 70.0 lb / 31.8 kg
    Dobsonian Base: 66.0 lb / 30.0 kg
    Fully Assembled: 164.0 lb / 74.4 kg, with weights

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