Your dome stays safe even if the computer freezes
Remote and unattended observatories depend on a working computer to run the automation software. But computers sometimes freeze or hang, and when that happens, most automation setups simply stop responding. The dome stays open, the telescope keeps tracking, and nobody is there to notice.
CloudWatcher includes a built-in watchdog mechanism to handle exactly this scenario. Because it communicates continuously with your PC, it can detect the moment that communication stops and trigger a relay to close the dome.
How the watchdog works
CloudWatcher and your PC maintain an ongoing dialog: the automation software talks to the CloudWatcher continuously, and that's how weather data flows in. This same channel doubles as a watchdog.
If the PC freezes, crashes, or loses power, that dialog stops. CloudWatcher notices communication has gone silent and switches its output to UNSAFE. Your automation software—or a direct relay connected to the CloudWatcher—can use this UNSAFE signal to close the dome and park the telescope.
Watchdog sequence: what happens when the PC freezes
The "UNKNOWN generates UNSAFE" setting
The key to this feature is a single option in the CloudWatcher software: "UNKNOWN generates UNSAFE". When this is enabled, any state that CloudWatcher cannot determine—including loss of communication with the PC—is treated as if weather conditions are unsafe.
This setting is especially valuable for remote observatories where you cannot be physically present to intervene if something goes wrong overnight.
AC power failure protection: a bonus safety net
The same mechanism provides a second layer of protection: it also handles mains power failures, provided your CloudWatcher itself is on ordinary house power, with no UPS of its own.
If the power to your observatory goes out, the CloudWatcher shuts down immediately: it has no backup supply. Your PC, if it's running on a UPS or backup inverter, keeps going and notices it's no longer receiving a dialog from the CloudWatcher. That silence is exactly what "UNKNOWN generates UNSAFE" is watching for: the software switches to UNSAFE and can act on it, even though the CloudWatcher itself is already offline.
I just noted some nice unexpected feature in the CloudWatcher. If the user checks 'UNKNOWN generates UNSAFE', the CloudWatcher makes a nice AC power fail feature. No power ⇒ no dialog ⇒ UNSAFE. In our installation the CloudWatcher is on the house supply (not on an uninterruptible power system), so in case of power loss, the computer—which operates on a backup inverter—gets the UNSAFE event and closes the dome. It is really interesting for remote setups.— Vincent Steinmetz, CloudWatcher user
What you need to set this up
- A CloudWatcher (any model) connected to your observatory PC
- CloudWatcher software running on the PC, with "UNKNOWN generates UNSAFE" enabled
- A dome controller or relay connected to the CloudWatcher relay output
- For power-fail protection: a UPS or backup inverter powering your PC (and whatever closes the dome), so it keeps running and can react after the CloudWatcher itself loses mains power
Configuration is minimal: enable the single option and verify the relay output triggers correctly. The feature is always active once enabled—and it's already proven itself: Vincent found out first-hand one Christmas night, when the observatory was left unattended and lost communication overnight. The next morning he confirmed the scope was nicely parked and the dome closed, thanks to the CloudWatcher alert script.