Xerxes Modular Drive Concept

All Xerxes Scientific telescope mounts are built on a family of 240mm diameter core drive modules. Each drive module comprises a high performance multi-pole high torque brushless DC motor, a Renishaw absolute optical encoder, and a shaft/bearing/housing assembly. Modules have a standardized bolt pattern and mounting holes, but use a common 200mm encoder ring which is twice as accurate as competitors using a 100mm ring. Different modules utilize different motor cores, and are upgradable within the same core length. All drives are operated using high performance industrial servo controls which operate via the CANopen industry standard protocol. This mount is intended to be used in cluster arrays which comprise many mounts all being remotely controlled.

TETRA Dual Sided Telescope Mount Family

The TETRA Dual sided equatorial telescope mount is ideal for carrying four to six telescopes, placing two or three on each side of the declination axis. The complete mount comprises either a 33 or a 60 newton-meter rated RA (Right Ascension) drive module and a dual sided 33 newton-meter declination drive module. One side of the declination axis is equipped with an actuatable / adjustable hinge mechanism which allows the telescopes on that side to be offset in RA by up to 2.5 degrees. This mount is used as the basis for our four and six telescope payloads. To specify a complete mount in this family, you have three choices of RA drive: 33 newton-meter (standard) torque, 60 N-m (high) torque, or 60 N-m high rigidity (used for high payloads). Next, select your mounting options for each side: either direct bolt-on, or two "P" type dovetail saddles, and finally, select accessories for mounting your telescopes. Accessories include mounting plates with individual tilt adjustment and actuation. See the accessories page for more information.

 

JPL mount
  • 26 bit absolute encoders on each axis
  • 50 to 75Kg payload each side (up to 150Kg total)
  • Typical tracking accuracy 0.5 arc sec in five minutes
  • Remote tilt control (collapse all telescopes to the same point or mosaic mode)
  • No meridian flip (tracks across meridian)
  • Dual gain schedule for safe slewing
  • Slews up to 50 degrees/sec
  • Up to 60 Newton-meter continuous torque(RA)
  • Up to 200 Newton-meter peak torque (RA)
  • 33 Newton-meter continuous torque (Dec), 100N/m peak

 

Pricing ranges from $24K to $34K depending on options and quantity. Contact us for more detail.

ENA Single Sided Equatorial Mount Family

The ENA sided equatorial telescope mount family uses the same modular drive concept but utilizes a single sided drive on the declination axis. The mount simply consists of two drive (motor) modules and a bracket and counterweight kit which connects the RA drive to the declination drive. The bracket and counterweight kit can be custom fabricated to your specifications or modified in the future if your use case changes. Example configurations are semi-offset, GEM-like (as shown), and fork mounts (with one driven side). You also can fabricate your own support structure or retrofit the drive to an existing legacy mount.

tandem RASA

 

  • 26 bit absolute encoders on each axis
  • Up to 75Kg payload
  • Typical tracking accuracy 0.5 arc sec in five minutes
  • No meridian flip (tracks across meridian)
  • Dual gain schedule for safe slewing
  • Slews up to 50 degrees/sec
  • Up to 60 Newton-meter continuous torque(RA)
  • Up to 200 Newton-meter peak torque (RA)
  • 10 to 33 Newton-meter continuous torque (Dec), 100N/m peak

 

Luggable Single-Arm Mount (In Development)

The single arm compact mount is currently in development. It uses a lower operating voltage and lower torque motors (five and ten newton-meters) to reduce the cost and weight of the product. It is suitable for telescopes up to a ten inch SCT size. Like all Xerxes mounts, it does not require a meridian flip when the telescope crosses the meridian. When properly balanced, it tracks exceptionally well, but the small torque rating in declination requires that you balance out any imbalance from your imaging train or small accessory telescopes..

tandem RASA

 

This product is still in development. Note that there is no guide scope in the setup, which comprises a Meade 10" f/10 SCT with no reducer and a ZWO ASI6200mm mono camera. You can see example images from this setup (and others) on my astrobin page here. Check back for more information.

 

Control Software

Xerxes mount control software is agnostic to the electronic servo control design or manufacturer, or most details of the mount drive motors and encoders. This is possible due to the development of very high performance industrial motion controllers for the machine tool industry, coupled with the use of open control protocol standards, e.g. CANopen. The Xerxes control software can be thought of as an astronomy layer which operates on top of a CANopen protocol stack. Many companies make servo drives which operate via the CANopen protocol, and as long as there is a sufficiently high performance absolute encoder to provide feedback, the Xerxes software can control the mount. This means your investment is better protected against obsolesence than fully proprietary solutions and you also get the benefit of the performance, monitoring, tuning capabilities, and diagnostics that the servo drive vendors provide.

The connection to the servo drives is simply a single CAN bus which connects to the two servo drives, one per axis. Additional axes can be added in the future for rotators or other precision motion control hardware. The connection hardware is a simple CAN to USB dongle (PCAN-USB). In a telescope mount cluster, each NUC computer controls one mount plus the local (slow) instruments such as focusers, and connects via ethernet to the host application which controls the mounts.

screenshot
  • Windows standard application, runs on Windows 7 and later on a dedicated NUC
  • Full mount manual control
  • Supports pointing models and variable rate tracking for unguided imaging
  • ASCOM driver available
  • Accepts guide commands through the ASCOM interface (no mechanical switch input provided).
  • Remote connection using Ethernet datagrams. UDP datagram protocol is publicly available.
  • 100ms response time via Ethernet remote control
  • User tuneable servo loop parameters during operation
  • Highly configurable servo drives via COTS tuning and control tools
  • Satellite tracking utility (beta)

Alt-Az and other configurations

All Xerxes mounts can mechanically operate in alt-az mode (primary rotation axis vertical) or in alt-alt (primary rotation axis horizontal) mode. Three axis control software is currently in development for these configurations, or you can implement your own using "native mode" control via the UDP datagrams.

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