ASCOM Dome Control

The ASCOM model of specifying software interfaces for common telescope components has become ever more popular and widely supported. The range of devices includes tentaive support for digital cameras, full support for filter wheels, telescope interfaces, focuser controls and dome controls. More than that, the installed package also prvides default software componentsa for the most common pieces of kit, software development stubs for those who want to develop their own and a useful set of chm help files to support this.

A lively community on yahoo groups and their own website at ASCOM web page also provides useful support and ideas.

On this base a lot of people have built their own custom interfaces to custom components. In this case this means a custom interface between my wireless dome components and an ASCOM-compliant dome controller. The base code for this is courtesy of John Winfield, originally from George Denny.

The implementation of the dome controller under the ASCOM standards in VB6 requires an ASCOM-compliant dome class object, a hardware-specific systems interface and a largely unchanging bookkeeping layer. In my case the hardware is based on the I2C bus ( a two-wire, multi-drop serial protocol capable of 400Kb over long distances ) and assorted components from DevaSys and Robot Electronics UK which provide the motor controllers, flux-gate magnetometer, LCD display etc as described on Wireless Observatory.

The dome link to the computer is two-pronged - one to the motor controller and display which can be wired since it is stationary, the other is a wireless link to the magnetometer which is an absolute direction indicator and moves with the dome.

The link to the source code for this project provides the source code and installation instructions at VB6 ASCOM dome .

The install sub-directory contains the scripts required to register and un-register the COM components of the ASCOM interfaces. Replace the references to the executable with your own if you want to use this software and that's largely it.

The current status of this project is that the links to and control of the motor controller and LCD display work, the compass interface works but the battery driving it is flaky so needs beefing up. The rest is in the process of being de-bugged. Since this code is third-generation largely, I expect it to work almost from the get-go.