SkyWalker-Servo's specifications


High quality Swiss made DC servo motors.
Iron-less rotor design featuring high power density. Provides for small Servo Drive Unit design and very efficient battery powered operation.
Long-life metal brushes: not standard graphite brush (limited life) motors.
Extremely smooth low speed "cog-less" performance.

Gear reduction:

Custom-made gear reduction included in each Servo Drive Unit.
High precision (not commercial quality) components (e.g. gears/bearings/shafting).
All-metal gears: no plastic gearing involved.

Drive electronics:

High efficiency power MOSFET 4-quadrant (i.e. "push/pull") drive.
Full digital design featuring 32-bit servo control.
"Flash" re-programable firmware providing upgrades from Internet download.
Complete protection against overload (avoids gear, motor and electronic damage).

Accuracy and resolution:

Servo motor position is controlled to 0.09 arcsecond on G-11/HGM-200/GM-8/CI700.

Servo Drive Unit enclosures:

Fully-machined black anodized aluminum gearboxes and electronics enclosures.
Laser engraved graphics (i.e. connection and indicator labels).
One-piece design that directly attaches to G-11 with no additional adapter blocks or plates.
Designed to be free from obstructing any Losmandy accessory such as encoder gear covers, "spindle- type" clutch knobs or high-resolution Losmandy encoder option. The Servo Drive Unit design protrudes into the path of the mount's moving parts by no more than the original Losmandy stepper motors.

Power supply

12v operation (11.0v to 14.2v allowed).
<300mA typical when tracking (with no optional accessories such as dew heaters, axial encoders, etc. attached).
3A maximum when slewing, typically much lower (load dependent).

Slew rate

Maximum slew rate 8.0°/sec.
Maximum recommended slew rate: 6.5°/sec for G-11/GM-8/CI700 and 5.0°/sec on HGM-200.

Axial encoder inputs (MJ-45, used in System mode):

Connects optional optical encoders for closed loop operation.
    - Supports standard quadrature-output encoders.
    - Supports Tangent Instruments™ pin-out and Astrometric Instrument's enhanced encoder pin-out (i.e. provides axial index input for alignment from indices).
Detects up to 20,000 encoder quadrature transitions per second.

Autoguider inputs (MJ-12):

Connects to an autoguider such as the SBIG ST-4.
The autoguider corrects at the currently selected SkyWalker1 pan/correction rate.

HP1 handpaddle:

Included with SkyWalker1 purchase
14 ft (3m) coiled cord
Powered from SkyWalker1
3.60" x 5.75" x 1.20" (92mm x 146mm x 31mm) excluding cord

Built-in peripheral support:

Electric focuser port (3.5mm phono jack, for 9v focusers) providing variable speed drive (up to 250mA).
Illuminated reticle port (3.5mm phono jack) providing variable output (up to 24mA) for cable-driven LED illuminated reticle eyepieces.

Size (excluding connectors):

Both RA and Dec Servo Drive Units: 5.2" long x 2.9" wide x 2.3" thick (132mm x 74mm x 58mm)

Control switches:

System/SkyWalker-mode select


Programmable Mechanical Error Correction (PMEC)
Battery status
Operational status (System/SkyWalker-mode and "Celestial Sync")

Internal Time-base Accuracy:

+/-30ppm from -20C to 50C ambient

Environmental Requirements:

-20C to 50C ambient
5% - 95% relative humidity, non-condensing


RA Drive Unit:
  - Power: 2.5mm power jack.
  - Communications: MJ12 (4 wire phone type) RS232. Provides connection to PC running SkyGuide Telescope Control System software.
  - Handpaddle: MJ45 (8 wire) HP1 and SkyGuide "smart handpaddle" compatible.
  - Axial Encoder: MJ12 (6 wire). Directly connects to Tangent instruments (including Losmandy and Celestron) digital setting circle encoders (cables included).
  - Connection to Dec Drive Unit: DB9 (9 wire) shielded "high flex" connection.

Dec Drive Unit
  - Autoguider port: MJ12 (6 wire). SBIG compatible.
  - Focus port: 3.5mm Phono plug. Provides direct Handpaddle control of popular motorized focusers.
  - Reticle port: 3.5mm Phono plug. Provides adjustable power source for illuminated reticle eyepiece. Brightness and "blink" adjustments provided.
  - TCS port: MJ12 (6 wire). Provides for Telescope Control System (TCS) expansion to one or more accessory controllers.
  - Axial Encoder: MJ12 (6 wire: same as on RA)
  - Connection to RA Drive Unit: DB9 (9 wire) shielded "high flex" connection.

"Mis-pluggins" will not cause SkyWalker or peripheral damage.
Back to SkyWalker-Servo Overview

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