Sky-Watcher StarGate Synscan 20" 508mm Truss Tube Dobsonian Telescope with Computer Drive

Sky-Watcher StarGate Synscan 20" 508mm Truss Tube Dobsonian Telescope with Computer Drive

Due to high demand and global product shortages due to the pandemic, please call for availability.

The StarGate 20" Dob - your portal to the sky.

Large diameter telescopes deliver outstanding resolution and clarity. Collapsible models are essential for portability. The StarGate 18" is very portable. The base and the optical assembly can be completely dismantled to fit into small vehicles, then easily assembled for an evening of stargazing.

As scopes grow larger, a number of concerns are introduced. Mirror weights increases, cooldown times increase, and mirror figures can be affected.

Advanced Mirror Design

The StarGate 20" employs a tapered primary mirror design with moulded sagittal supports. The thinner mirror coupled with support veins running from the edge to the centre helps reduce unwanted weight and thermal mass while maintaining the precise figure of the mirror. The secondary mirror is manufactured with cells molded in the back to reduce weight and thermal mass, while increasing the surface area to further reduce cool-down times.

Collapsible Design

The optical tube and rocker base break down to roughly 22 discrete parts. The upper cage remains as one piece holding the secondary mirror and focuser. The lower case retains the primary mirror.


The included Synscan computer drive will slew the telescope to over 42,000 objects, and keeps them in view without the need to nudge the telescope.

The built-in high-resolution axis encoders permit the user to push the scope to new positions without having to re-align the system, blending the advantages of a push-to telescope, with the sophistication of a go-to computerized telescope.


  • Tapered primary mirror with sagittal supports and cellular secondary mirror design to minimize weight, reduce cooldown time while maintaining figure
  • Parabolic primary mirror to focus all light rays to a common focal point
  • Clip-less tapered mirror design offers excellent stability and acclimatization
  • Sturdy collapsible Newtonian Reflector Optical Tube Assembly
  • Automatically finds and follows astronomical objects
  • Includes "The Beginners Guide to Using Telescopes" written by our knowledgeable staff.


  • Aperture: 508mm (20")
  • Focal Length: 2000mm
  • Focal Ratio: f/3.9
  • Mirror Type: Parabolic
  • Focuser: 2" cast aluminum, dual speed crayford, with lock screw
  • Eyepieces: 28mm (68x) LET eyepiece (2") and 10mm (190x) Plossl (1.25")
  • Barlow lens: Available (sold separately)
  • Finderscope: 8x50
  • Mount Type: Dobsonian Altazimuth
  • Tracking System: Synscan computerized drive
  • Polar Finder: Not Available
  • Camera Capable:
    • USB imagers
    • All-in-one cameras via universal digital camera adapter
    • DSLR/SLR (requires T2 ring)
    • Above cameras and adapters sold separately
    • Short exposures with Synscan computerized tracking system installed
  • Shroud
  • Truss clamps
  • Two year limited warranty

Computer Drive Specifications

  • SynScan computerized go-to system
  • Over 42,000 objects in the database including complete Messier, NGC, and IC catalogues
  • RS-232 port
  • USB port
  • Flash-upgradeable firmware
  • Accuracy enhanced by software collimation error (mount mechanical error) compensation
  • GPS upgradeable (sold separately)
  • Optically encoded closed-loop drive system
  • Servo motor drives
  • 9 slewing speeds:
    • 1x (0.25arc-min/sec), 2x (0.5 arc-min/sec), 8x(2 arc-min/sec)
    • 16x(4 arc-min/sec), 32x (8 arc-min/sec), 200x (50 arc-min/sec)
    • 400x (1.6°/sec), 600x (2.5°/sec), 800x (3.3°/sec), 1000x (4.2°/sec)
  • High resolution axis encoders
  • Includes 12v car plug-in adapter
  • Power requirement: 11v to 16v DC, 5A @ 11v, 3A @ 16v, tip positive
  • AC adapter: sold separately, switching-mode regulated power supply highly recommended


  • Height of eyepiece (pointed to Zenith): 200 cm (79")
  • Height of optical tube and assembled base: to be determined
  • Upper cage length: to be determined
  • Upper cage weight: 5.5 kg (12 lbs)
  • Truss pole weight: 1.2 kg each, 7.2 kg total (2.6 lbs each, 16 lbs total)
  • Mirror box weight: 31.8 kg (70 lbs)
  • Base diameter: to be determined
  • Base weight: 30 kg (66 lbs)
  • Counterweights: 3 x 1 kg, 3 kg total (3 x 2.3 lbs, 6.9 lbs total)
  • Total Weight: 74.5 kg (164 lbs)