CloudWatcher is an astronomy utility which enables Mac-based astronomers to use a hardware device to monitor relevant weather conditions, such as cloudiness and rainfall. The device is able, in combination with the CloudWatcher software, to activate a hardware switch in response to adverse conditions which can trigger safety measures such as closing an observatory roof.

The hardware device concerned is the economical AAG CloudWatcher, available from Lunatico Astronomia, Spain. CloudWatcher reproduces the look-and-feel of the Windows software which ships with the device, and can interoperate with that software. But it also offers many features in addition.

• reproduces most features of the AAG_CloudWatcher Windows software;
• automatically detects the optional wind sensor;
• provides wind gust speed as well as configurable averaging;
• provides a measure of sky-temperature standard deviation;
• reads a sky quality meter (Unihedron SQM-LE), if available on the local network and plots the readings;
• ability to fire a script to TheSkyX in case of unsafe conditions, which will cause any mount controlled by TheSkyX to park;
• can send scripts to SX-IO (a product of to control an Oculus all-sky camera as a function of cloud and brightness;
• plots are labelled with natural round values.

CloudWatcher is compatible with AAG CloudWatcher firmware version 3.x (before the introduction of the anemometer option) and version 5.x (with the anemometer option). Firmware versions 1.x, 2.x and 4.x were not distributed.

What’s New

Version 3.0.5

This is a bug-fix version, addressing the following problems:
Fixed a problem whereby the CloudWatcher hardware blocks after several days of use, requiring a power cycle before it can be used again (this was due to leaving too short an interval between commands)
Fixed an issue which leads to the Rain Sensor heater being applied at 100%, constantly (linked to the previous bug).
Fixed a bug introduced in Build 65 whereby some date/time fields reported UTC instead of local time.
Fixed an issue which could cause an inconsistent approach to formatting the Boltwood interchange file, depending on the users’ locale.
Fixed an issue which prevented the Ts equation from being displayed in the Temperature Compensation window.
Fixed a bug which could cause an exception at the end of the last day of the month.
Fixed a bug which could cause a hang if a selected SQM-LE is unavailable.


14.7 MB

OS X 10.10 or later, 64-bit processor



Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.