PLEASE NOTE 2026: If you are writing a driver or an application, we strongly encourage you to write for ASCOM Alpaca. You can write a Windows driver for Alpaca as easily as one for the old COM. There is a cross-platform library for applications.
What are ASCOM Alpaca and Classic ASCOM?
- ASCOM stands for Astronomy Common Object Model
- Primarily a set of simple elegant API specifications for astronomical devces and applications
- Eliminates barriers to both device and app developers who would otherwise need to provide special logic for every combination of device and app.
- Eases the pain of troubleshooting by clearly dividing application and device with a universal interface.
- ASCOM COM and Alpaca are both language independent.
- Alpaca is OS independent, no need for Windows anywhere.
- Alpaca and ASCOM COM are 100% interoperable now easing migration from old to new
- A new Alpaca device is immediately usable from unmodified Windows apps that currently use ASCOM COM.
- Under the hood, Alpaca uses the modern and open network protocols of HTTP and JSON for data transfer at the low-level.
- Please note that Windows is not required for Alpaca!
What Can I Do Right Now With Alpaca and ASCOM?
- An Alpaca device can be a standalone WiFi device, no server or cable needed. These are already appearing.
- Writing a driver? Make it for Alpaca! Ask for guidance on the ASCOM Developer Forum.
- Legacy Windows applications can use Alpaca devices without any modification. The Windows Chooser can find and select an Alpaca device and automatically build a "permanent" ASCOM (COM) driver that can be used by any legacy ASCOM COM application on that system immediately.
- Legacy Windows-resident devices (mounts, cameras, dome controllers, etc.) can have Alpaca interfaces added to them without any modification. So your sophisticated mount controller can be used by an Alpaca speaking app on any platform (and there are already several).
- The ASCOM Initiative provides an extensive set of tools, libraries, templates, samples, and documentation to help developers get started. The focus is on C# and Python, both are modern, high-level, and cross platform.
- Alpaca developers in any lnguage continue to use the exact same mature APIs that have been used in ASCOM for 20+ years.
- Same API and common protocol means the technical risks for using Alpaca are very low.
How Does This All Relate?
The graphic below shows how our group, ASCOM itself, and both ASCOM Alpaca and Classic ASCOM COM relate. To see how this has been possible, and how it started, see About Alpaca and ASCOM and History of ASCOM COM and Alpaca Development.
If you want more info on why ASCOM was created and how ASCOM (Alpaca and COM) works, see the About Alpaca and ASCOM section. It tells the story in pictures. Otherwise proceed to the section that addresses the reason you came here, in the orange menu on the left.
What has Been Happening?
ASCOM has undergone a rapid transformation from Windows-only to a universal technology. Classic ASCOM has been a fundamental cornerstone of astronomy innovation on the Windows platform. Now we have ASCOM Alpaca, a new way to accomplish the same things but via network connectivity and on any platform, even embedded controllers. Both Alpaca and Classic ASCOM seamlessly operate in the background of many of the products you are currently using. Both provide the same universal language so that any astronomy app/program can connect to any astronomy device which complies with the ASCOM standards. ASCOM has become essential through simplification and standardization. Without ASCOM we would not have seen the explosive growth and innovation we have experienced in the field over the last 20 years.
