03. Installing an ASCOM Alpaca Bridge - gordtulloch/Galileo GitHub Wiki

Installing an ASCOM Alpaca Bridge on Windows

Galileo talks to hardware through two protocols: INDI (see 02. Installing INDI) and ASCOM Alpaca, covered here. It does not use Windows ASCOM/COM drivers directly.

When to use Alpaca instead of INDI

Use Alpaca when:

  • Your device already ships a native Alpaca driver or firmware (e.g. a ZWO Seestar's built-in Alpaca server, ASCOM Platform 7 drivers, or a growing number of Alpaca-native devices). In that case there's nothing to bridge — just point Galileo at the device's IP and port directly.
  • Your device only has a traditional Windows ASCOM/COM driver, and you want Galileo — potentially running on a different machine, or on macOS/Linux where COM doesn't exist at all — to reach it over the network. This requires a bridge that exposes the COM driver as an Alpaca endpoint, covered below.

You can mix INDI and Alpaca devices freely within one Galileo Pier.

Installing the bridge

If your mount, camera, focuser, or other device only ships a Windows ASCOM/COM driver, you can expose it to Galileo (and any other Alpaca client) over the network using ASCOM Remote, the official bridge maintained by the ASCOM Initiative. It runs on the same Windows PC as your COM drivers and translates Alpaca HTTP requests into COM calls behind the scenes — Galileo itself never needs to know COM exists.

1. Prerequisites

  1. Install the ASCOM Platform. Download the latest installer from ascom-standards.org/Downloads and run it. This installs the COM infrastructure that both your device drivers and ASCOM Remote depend on.
  2. Install your device's native ASCOM/COM driver from the manufacturer (mount, camera, focuser, filter wheel, etc.) and confirm it connects correctly using the vendor's own tool or the ASCOM Device Hub/Diagnostics utility that ships with the Platform. Get this working locally before adding the network bridge — it rules out driver problems before you start debugging the bridge.

2. Install ASCOM Remote

  1. From the same ASCOM downloads page, download ASCOM Remote (listed under "Remote / Alpaca" tools; it may also be offered as an optional component in the main Platform installer, depending on version).
  2. Run the installer. It adds an ASCOM Remote Server application plus a small system-tray configuration UI.
  3. Launch ASCOM Remote Server from the Start menu. The first run opens its configuration page in your browser (it's a local web UI, typically at http://localhost:32323/setup).

3. Configure the bridge

In the ASCOM Remote configuration page:

  1. Under Setup → Device Configuration, add a new device entry for each COM driver you want to expose (mount, camera, focuser, etc.). Pick the installed ASCOM driver from the dropdown for each.
  2. Each device is assigned an Alpaca device type and device number (e.g. Telescope #0, Camera #0) — note these down, since Galileo's device picker will show them the same way.
  3. Under Setup → Server Configuration, confirm the IP address and port (default 32323) ASCOM Remote listens on. If this PC has multiple network adapters, bind to the one reachable from wherever Galileo runs (or 0.0.0.0/all adapters if you're unsure).
  4. If Windows Firewall prompts you when the server first starts, allow access on Private networks (or add a manual inbound rule for TCP port 32323) — otherwise devices on your LAN, including Galileo running on another machine, won't be able to reach it.
  5. Start (or restart) the ASCOM Remote Server so it begins listening.

4. Verify the bridge before connecting Galileo

Alpaca devices support discovery and a plain HTTP management API, so you can sanity-check the bridge without Galileo:

  • Open http://<bridge-pc-ip>:32323/setup from a browser on another machine on the same network — you should see the same configuration page.
  • Open http://<bridge-pc-ip>:32323/management/apiversions — this should return a small JSON document, confirming the Alpaca API is responding over the network (not just on localhost).

5. Connect from Galileo

In Galileo's device connection dialog, choose Alpaca as the driver, enter the bridge PC's IP address, and set the port to 32323 (or whatever you configured in step 3). Scan for devices — the mount, camera, or other equipment you added in ASCOM Remote should appear using the same device numbers you noted earlier. This works whether Galileo is running on the same Windows PC as the bridge, or remotely from macOS, Linux, or a Raspberry Pi elsewhere on the network — the whole point of the bridge is that COM never has to leave the Windows box, only Alpaca traffic does.

6. Notes and troubleshooting

  • ASCOM Remote vs. Alpaca simulators: don't confuse ASCOM Remote (the bridge for real COM drivers, above) with the ASCOM Alpaca Simulators package, which only exposes simulated devices for testing. If you just want to test Galileo's Alpaca support without hardware, the simulators are a faster path — the Getting Started Guide mentions them running on port 11111 by default.
  • One bridge PC can serve many devices. You don't need a separate instance of ASCOM Remote per device — add every COM driver on that machine to the one running server, each with its own device number.
  • Port already in use: if 32323 conflicts with something else (e.g. a Seestar's own built-in Alpaca server also defaulting to that port), change ASCOM Remote's listening port in Server Configuration and use the new port when connecting from Galileo.
  • Discovery finds nothing: Alpaca's UDP auto-discovery only works within the same broadcast domain (same LAN segment/VLAN). Across subnets, VPNs, or Wi-Fi isolation-enabled routers, enter the bridge PC's IP address and port directly in Galileo instead of relying on scan/discovery.
  • Nothing responds at all: check that ASCOM Remote Server is actually running (not just installed), that the underlying COM driver still connects locally, and that Windows Firewall isn't silently blocking the port — the /management/apiversions check in step 4 isolates network/firewall problems from driver problems.