Focuser

The focuser controls the focal-plane position to maintain sharp images across changing thermal conditions, filter changes, and optical alignment. SkyNode commands the focuser through manual operations and through the imager autofocus task.

Config shape

{
  "device_type": "focuser",
  "driver": "ascom" | "simulator",
  "driver_configs": {
    "ascom":     { /* see below */ },
    "simulator": { /* see below */ }
  }
}

Drivers

ascom — production

For any ASCOM-conformant focuser on Windows.

"ascom": {
  "prog_id": "ASCOM.DriverHub.Focuser"
}

Key	Meaning
prog_id	ASCOM ProgID of the focuser driver. Default ASCOM.DriverHub.Focuser — the ASCOM Driver Hub, which proxies to whatever focuser-specific driver you've configured inside Driver Hub. Set explicitly when you'd rather load a specific driver directly (ASCOM.OptecFocuser.Focuser, etc.)

Notes:

• ASCOM focusers typically expose an absolute step position; the autofocus executor walks positions, takes exposures, fits a metric, and returns to the best position. The driver app's step-size and step-range settings are what define the resolution available to the executor.
• Temperature compensation is optional and configured inside the ASCOM driver app, not in SkyNode. If your focuser supports it, enable it there.

simulator — testing only

Paper focuser. Accepts step commands and reports the new position; doesn't simulate optical defocus.

"simulator": {}

Troubleshooting

• "Autofocus never converges." Three flavors: (1) the focuser range is too small relative to ambient drift, (2) the autofocus strategy's step pattern is wrong for your scope, or (3) the image-quality metric the executor uses is being confused (saturated stars, clouds, very crowded fields). Inspect the autofocus log entries on the telescope log book via the website.
• "Focuser drifts during long exposures." Without temperature compensation, mechanical thermal drift is the most common cause. Enable temperature compensation in the ASCOM driver app if available, or schedule periodic mid-night refocus runs.
• "Focuser reports completion but image is still blurry." Same family of issues as "autofocus never converges" — usually about step resolution or metric sensitivity rather than the driver itself.