Astrometric Instruments: Product Line

SkyWalker-Servo Introduced

SkyWalker-Servo is a complete telescope control system utilizing high quality DC servomotors, sophisticated/highly-integrated electronics, and precision gear reduction and mechanical components. SkyWalker-Servo is the culmination of a decade of telescope control system development at Astrometric Instruments. SkyWalker-Servo is designed as both a control system upgrade (as our SkyWalker-Servo retrofit kit), and for installation as original equipment, on Losmandy (G-11, GM-8 and HGM-200), Celestron (CI700) and other commercial telescope mounts.

• See the SkyWalker-Servo Spec Sheet

SkyWalker-Servo's major features and benefits

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SkyWalker-Servo incorporates DC servomotors which include built-in and continuous position feedback providing extremely accurate tracking. These motors provide very large dynamic range (i.e. difference between lowest speed and highest speed). Therefore, only one compact and powerful servomotor is necessary per axis to provide very smooth and accurate tracking and high-speed/high-torque slew (6.5°/sec on G-11).

•	The SkyWalker-Servo design spares nothing in quality. This means more expensive components than could have otherwise been used. Examples include very high quality Swiss-made DC servo motors, high precision gearing, and fully-machined (from solid aluminum) gearboxes and electronics enclosures. Of particular note is SkyWalker-Servo's high-quality (AGMA10) all-metal gear reduction included in each Servo Drive Unit. This gearing preserves the accuracy that the DC servomotors are capable of delivering and is a big improvement over the low quality gearboxes used in other systems.
•	SkyWalker-Servo is a very compact and fully-integrated system that does not require a separate enclosure on the mount's pier, tripod or elsewhere. All of the electronics have been designed into the "Servo Drive Units" along with the servo motors and gearing. Benefits include:
	-	For the Losmandy mounts, SkyWalker-Servo does not mechanically interfere with any known mount option, such as spindle-type clutch knobs, the high resolution encoder option or encoder gear covers. In fact, the Servo Drive Units "protrude" into the path of the mount's moving parts by no more than the original Losmandy stepper motors.
	-	The Servo Drive Units adapt to the mount with little (for the Celestron CI700) or no (for Losmandy mounts) special hardware.
•	SkyWalker-Servo does not require a bulky cable harness. Unlike other systems, there are no connections to a box on the pier that has to be removed every time the system is packed-up. Benefits include:
	-	Ease of setup. The "Servo Drive Units" attach to the mount permanently. There is no need to remove them for transport.
	-	Reliability. There are very few critical cable connections that must be detached for transport.
	-	Convenience of use. The cable tangle, from an electronics box mounted on the pier, is eliminated.

SkyWalker-Servo's functionality All SkyWalker systems, new and old, share the same functionality. Since our first commercial SkyWalker model in 1995, we have carefully designed all our SkyWalker systems to allow free or "at cost" functional upgrades. We strongly believe that our customers deserve to have their investment protected. SkyWalker's quality, painless upgrade path, and our strong commitment to customer support protects your investment. Together with its handpaddle, SkyWalker is a stand-alone telescope controller or, when used with a PC running SkyGuide-Win, a complete full featured telescope control system. These two levels of functionality are called SkyWalker mode and System mode. For complete details on these two modes visit our SkyWalker Functionality page. SkyWalker-Servo's HP1 handpaddle The HP1 handpaddle is included standard with all SkyWalker systems. It has been designed for ease of use under typically adverse astronomical observing conditions. Features include large, tactile and backlit buttons, clear indication of Slew / View velocities and track rate, peripheral control (e.g. Focus), and "assignable" keys. Complete details on the HP1 handpaddle can be found here. SkyWalker-Servo in detail The SkyWalker-Servo system includes three units:

1.	Right Ascension Servo Drive Unit
2.	Declination Servo Drive Unit
3.	Standard HP1 handpaddle OR SkyGuide "smart" handpaddle (a.k.a. SkyGuide-instrument, available soon).
There are NO other boxes or enclosures in the base system. All SkyWalker functionality is integrated into the two Servo Drive Units and handpaddle.
SkyWalker-Servo also ships with our SkyGuide-Win Telescope Control System software (see SkyWalker Functionality for complete details), a fused 6' power cord and 14' coiled RS232 communications cable. Custom cable lengths are available.
SkyWalker-Servo provides convenient connection for several telescope accessories. These connections are built-into the Servo Drive Units. In the above picture, most of the possible connections to SkyWalker-Servo are shown. These include:
•	On the Declination Servo Drive Unit:


	-	Autoguider connection labeled "AG".
	-	Electric focuser (e.g. JMI NGF) connection labeled "Focus".
	-	Cable-powered illuminated reticle connection labeled "Reticle".
	-	Declination Axial encoder connection labeled "Enc" (optional and not necessary for system operation).
	-	Telescope Control System expansion port connection, labeled "TCS", allowing for connection to future Astrometric Instrument's accessories.
	-	Connection to the Right Ascension Servo Drive Unit through a single high-flex cable.
•	On the Right Ascension Servo Drive Unit:
	-	RA Axial encoder connection labeled "Enc" (optional and not necessary for system operation).
	-	SkyWalker's handpaddle connection labeled "HP".
	-	RS232 communications connection labeled "Com".
	-	12v power connection labeled "Pwr".
	-	Connection to the Declination Servo Drive Unit through a single high-flex cable.
As mentioned above, SkyWalker-Servo is designed to not mechanically interfere with optional mounting accessories. In fact, on the Losmandy G-11, SkyWalker-Servo's compact design allows for movement up to the Celestial Meridian from the West (from the East in the Southern Hemisphere). This is further than the original Losmandy stepper motors allow. Movement from the East (from the West in the Southern Hemisphere) through the Meridian depends on the optical tube assembly but typically is 30 degrees (2 hours of RA). In the event that the telescope is moved by hand past the Meridian (SkyWalker does not allow this under computer control), a rubber bumper on the solid aluminum RA Servo Drive Unit enclosure safely stops the mount as shown at left.

The photo at right shows just how compact the Servo Drive Units are. Notice that the enclosure (with the exception of the backside cover) is formed out of two aluminum pieces CNC machined out of solid aluminum stock. The section on the right is the foundation of SkyWalker-Servo's precision gearbox. The other section provides very robust packaging of sensitive electronics and the servomotor. The LED indicators on the RA Servo Drive Unit are (from the top) Power, PMEC (Programmable Mechanical Error Correction), LowBatt and Sync (Celestial "synchronization").

SkyWalker-Servo provides plenty of torque to drive even the large Losmandy HGM-200 mount (shown left).