Twinstar FG80 mount

Posted on Thursday, January 23, 2025 by RICHARD HARRIS, Executive Editor

Twinstar recently announced that Mount Heads are now available, with five units in stock and ready for distribution. The FG80 mount is offered at its standard price of $4,532 USD / 4350 EUR plus VAT and shipping. Each kit includes a pier adapter compatible with tripods such as EQ6, EQ8, Meade, and iOptron Tri-Pier. The default counterweight holder shaft diameter is 30 mm, and adjustments can be made to accommodate specific weights, including those with larger or smaller diameters. An adapter for weights with larger holes can also be provided if needed.

Twinstar FG80 mount by Twinstar Astronomy

The friction drive operates using a small roller pressed against a larger disk. This system utilizes a large gear ratio, such as 1:500 or more, achieved through precise material selection and machining of the mechanical components. The system eliminates backlash, reduces periodic error to negligible levels, and offers a high stiffness compared to traditional gears. It does not require lubrication, provides smooth tracking, and achieves high efficiency.

The friction drive system enables precise sub-arcsecond tracking without requiring encoders or complex electronics. This approach reduces costs and simplifies operations, allowing astronomers to focus on observations. Despite the absence of encoders, the system maintains reliability and accuracy. Advances in software-based blind plate-solving techniques further enhance positioning precision, enabling sub-arcminute level accuracy quickly and without significant investment.

In many mounts, electronic encoders are used to counteract mechanical imperfections, but they add significant cost due to their high price and the need for specialized electronics. Twinstar’s system achieves high precision without encoders, avoiding these costs while maintaining durability and reliability.

The mount delivers tracking accuracy of 0.5 arcseconds with minimal deviation for extended periods. Longer exposure times or variable exposure delays are recommended in guiding software to mitigate atmospheric disturbances. Tracking performance is influenced by seeing conditions, which refer to atmospheric turbulence affecting image clarity. Even under moderate conditions, the mount exceeds the requirements for most observations and astrophotography tasks.

A typical guide graph generated with an FG80 mount carrying a load of 110 lbs / 50 kg, including the telescope tube and counterweights, shows consistent performance with minor fluctuations caused by seeing conditions. In most situations, the mount's tracking precision surpasses the demands of astrophotography.

The minimal guide scope focal length is the shortest focal length needed for accurate guiding during astrophotography. It ensures the guide scope can detect small star movements to maintain focus. This depends on the focal length of the main telescope and the pixel sizes of the cameras used in the guide scope and main telescope.

FG80 telescope friction mount APO


Friction Mount Twinstar FG80 specifications

  • Drive system: Friction 
  • Payload: 176.37 lbs / 80 kg 
  • Counterweight holder shaft diameter: 30 mm / Twinstar can reduce the shaft diameter for your weight, for example, to 28 mm, if needed.
  • Tracking precision: +/- 0.5 arcsec for unlimited time 
  • Control system: ASCOM / INDI / ASIAIR compliant 
  • USB/DC hub: 7 x USB 3.0 / 8 x 12V DC, max. 4A/port
  • Pointing accuracy: +/- 5 arcmin
  • Typical PE: (Arcsec RMS)     0 
  • Weight: 46.30 lbs / 21 kg 
  • Power: 12V, max. 20A 
  • Maximum current: max. 1.5A
  • Used material: anodized aluminum and stainless steel
     

Twinstar FG80 Mount Heads Now in Stock

Twinstar has announced that five mount heads are currently in stock and ready for immediate distribution. This availability allows customers to acquire high-quality, precision-engineered mounts without the usual wait time.

The limited-time promotion has ended, and the FG80 mount is now available at its regular price of $4,532 USD / 4350 EUR plus VAT and shipping costs.

The kit includes a basic pier adapter, which can be used with tripods such as EQ6, EQ8, MEADE, and iOptron Tri-Pier. The default counterweight holder shaft diameter is 30 mm. Twinstar can reduce the shaft diameter for specific weights, such as 28 mm for iOptron weights. If necessary, an adapter for weights with larger holes can be provided.

The friction drive, also referred to as a roller drive, consists of a small-diameter roller pressed against a large-diameter disk. The system operates on a simple principle: the small roller rotates the large disk, achieving a high gear ratio, such as 1:500 or more. Precise material selection and machining ensure the accuracy of all mechanical parts in the drive system.

The friction drive system is designed to have zero backlash and minimal periodic error. Without traditional gear teeth, the system offers very high stiffness, many times greater than other gearing systems. The drive system does not require lubrication, has high overall efficiency, and provides smooth tracking.

The friction drive system achieves sub-arcsecond tracking precision. It does not rely on encoders or complex electronic setups, providing a straightforward solution for users prioritizing precision without compromising simplicity. The absence of encoders enhances reliability and reduces operational complexity.

The friction drive system also benefits from advancements in blind plate-solving solutions. These software-based solutions, often free of charge, can achieve sub-arcminute-level positioning within minutes. This improves the accuracy and efficiency of astronomical observations without requiring significant additional investment.

Encoders are commonly used in telescope mounts to address mechanical imperfections in drive systems, enabling accurate tracking and position monitoring. However, they significantly increase the cost of mounts. Precision encoders can cost several thousand dollars each, and specialized electronics and software are required for constant correction calculations.

While mounts equipped with encoders provide sub-arcsecond tracking precision, they come at a high cost. The Twinstar team has developed a drive system that achieves the highest precision without using encoders or additional electronics. This system provides accuracy without compromising affordability or durability.

The telescope mount provides consistent tracking precision of 0.5 arcseconds over unlimited durations, with minimal deviation. Users are advised to employ longer exposure times or a variable exposure delay in PHD guiding software. This allows the guiding system to average out seeing conditions and reduce the impact of short-term atmospheric disturbances.

Seeing conditions, caused by atmospheric turbulence, are typically the primary factor affecting tracking precision. While the mount delivers high accuracy, the quality of the observing location and the current seeing conditions significantly influence results.

A typical PHD guide graph for an FG80 mount loaded with 110 lbs / 50 kg of equipment (including the telescope tube and counterweights) under moderate seeing conditions would show consistent guiding, with fluctuations primarily caused by atmospheric effects.

Even in less-than-ideal observing conditions, the mount's tracking precision exceeds the requirements of most observational or astrophotography tasks. By following these recommendations and utilizing the mount’s precision, users can achieve excellent results even under challenging conditions.

Twinstar FG80 Omegon APO


Minimal Guide Scope Focal Length

The Minimal Guide Scope Focal Length refers to the shortest focal length a guide scope should have to ensure accurate guiding during astrophotography or tracking. This value is determined by considering the following:

  • The focal length of the primary imaging telescope (in mm).
  • The pixel size of the camera used in the guide scope (in microns).
  • The pixel size of the camera used in the main telescope (in microns).
     

This calculation ensures that the guide scope can accurately detect small deviations in star position, allowing for precise guiding.

Twinstar FG80 RASA


Introducing the Twinstar FG80 / friction drive German equatorial mount

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