A cross platform standard for drivers maintained by the ASCOM Standards Committee. Alpaca is built on REST APIs.

Alpaca Discovery

A standard mechanism that allows client programs to find Alpaca devices and drivers running on the local network.


ASCOM is a set of interfaces and tools used to build drivers. ASCOM is maintained by the ASCOM Standards Committee. ASCOM runs on the Windows COM System.

ASCOM Chooser

The ASCOM Chooser allow programs to select and use ASCOM Drivers. As of Platform 6.5 it also supports the discovery and use of Alpaca drivers.


Backlash is a form of slack or play (a dead space when reversing direction of motion) found in almost any geared system. Although excessive backlash should be avoided some backlash is required to prevent jamming and to allow the gears to reverse direction.

Backlash Compensation

Backlash Compensation is a technique that minimizes the effect of Backlash in the position of a mechanism.

Device Type

The device type determines what features the focuser supports. This includes range and motor function.


An automated process that a focuser uses to find the home position, which is also the zero point.


A mode for non-homing focusers that reverses the direction of all moves IE in becomes out.


The smallest unit of motion a focuser motor can move. Position and move requests are measured in steps.

Step Size

How far in microns the physical focus position changes in a single step. This is used for unit conversion only; it does not change how the focuser moves.


A way to set the position for a non-homing focuser

Temperature Compensation

Temperature Compensation is a mode where the focuser corrects for changes in focus caused by changes in temperature. Temperature Compensation requires calibration.