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Gemini Telescope Design MOFOD MkII Fork Friction Mount

Gemini Telescope Design MOFOD MkII Fork Friction Mount

Product Number: GTD-MoFoD
Price starts at $14,375.00 and includes everything except the optional counterweight system and custom elevation range options.

Shipping is by freight.  Please inquire for complete costs.
Call 602-820-7962 For Pricing   
Gemini Telescope Design MOFOD MkII Fork Friction Mount

The Gemini MOFOD MkII Fork Mount is the ideal solution for demanding astronomy applications (serious amateur, public, school, society or professional observatories). The Modular Fork Design allows changing the OTA by sliding the fork arms in or out. MOFOD Fork Mount is the most stable observatory class mount with remote control (Read article about MoFoD – a Flexible Fork mount for observatory). Join the Gemini Friction Fork Revolution!

Why a Fork? Why not!

Gemini MOFOD MkII Fork Mounts have the following advantages over German Equatorial mounts

    No counterweight needed – smaller inertia can be rotated faster.
    No meridian flips needed – no lost time.
    No guider recalibration or field rotation needed.
    No collision with the pier is possible – more safety in remote mode.

Fork Mount Disadvantages?

In the past fork mounts were not as flexible for changing OTAs as German Equatorial mounts. The GTD Modular Fork Design allows for changing the OTA by simply sliding the fork arms out or in. Any compact telescope from 14 in. (340 mm) to 21 in. (540 mm) diameter can ride this fork.

What is Modular Fork Design (MoFoD)?

The GTD MOFOD Fork Mounts are easily separated into 4 main parts: the RA base, the horizontal arm (tube) and the two fork arms. The orthogonality of the main axes is adjustable, ensuring maximum pointing precision.  Two persons can do the setup in 1 hour with a set of allen keys.

Technical parameters

The mount rests on a robust RA head that sits in an aluminium casting, holding two large tapered roller bearings. The shaft upper (larger) diameter is 5.5 in. (140 mm). To drive the mount GTD choose friction drives for their very low PE and rock solid operation. The slight backlash present in large worm gears and the tendency to vibrate if unbalanced is absent with the friction drive and the slewing speeds are very high with low power consumption. Safety clutches are mounted in both axes to prevent damage to the drive system or the OTA.

To ensure precision in pointing and reliability in remote mode, high resolution encoders are mounted on each axis. The encoders have an absolute reference point that enables the driver to find the home position after a blackout or crash of the control PC. The stepper motors have 0.1″ resolution.

The optional 2.2 lbs. (1 kg) sliding weight inside the horizontal fork arm allows fine balancing the OTA for best operation. Coarse balancing is achieved by sliding both fork arms with the OTA in the correct direction.

The image below shows the tracking accuracy of the MoFoD

  • Materials: Zink plated steel, powder coated (base), cast aluminium, 6082 aluminium (RA housing and shaft), stainless steel, (fork arms), roller bearings, stepper motors, high resolution optical encoders.
  • ASCOM compatible stepper motor drive system
  • PE: cca 5” ptv in 30 minutes
  • Weight: RA base cca 110 lbs. (50 kg), Horizontal arm cca 26.5 lbs. (12 kg), Fork arms with drive cca 55 lbs. (25 kg)
  • Payload: 175 lbs. (80 kg)
  • Elevation range: 35-55 degrees (others upon request)
  • Azimuth adjustment range: +/- 5 degrees
  • Through the mount cabling
  • Pulsar2 drive system with built-in GPS
  • PC interface: serial, USB, LAN, Bluetooth (optional)
  • Pointing precision without modeling:  30 arc. sec. RMS
  • Slew speed: 4 deg/sec
  • Tracking precision, closed loop: 2"/15 minutes
  • Pier interface: 14.2 in. (360 mm) diameter
  • Accepted OTAs: from 10 in. (250 mm) up to 18 in. (450 mm) (optics diam.) or multiple smaller instruments. The typical OTA for a fork is any Cassegrain derivant (RC, DK, SC, MC) or a fast Newtonian. The fork has 23.6 in. (600 mm) free swing for the eyepiece end of the OTA.
  • OTA interface: 3” Losmandy female (400 mm male rails supplied upon request)
  • Encoder based tracking speed control for unguided imaging, cable routing in the RA shaft
  • 5 year warranty for all mechanical parts and 1 year for all electronic parts

Delivery times are approximately 8 to 10 weeks.

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