CloudWatcher – Hydreon rain sensor version


High precision, low-cost system for monitoring the weather conditions and measuring the sky-quality.

Adapted version to work with the Hydreon RG-9 Rain sensor.

Comparison between the Capacitive sensor and the Hydreon sensor

Please note, the RG-9 rain sensor does not distinguish condensation from rain, so we do not recommend it in high humidity environments.

Estimated shipping time: 9 days

This CloudWatcher is an adapted version to work with the Hydreon RG-9 Rain sensor (which is sold separately).

(no other rain sensor installed – for rain information, the RG-9 is needed).

CloudWatcher, watching the sky since 2008.

CloudWatcher with anemometer and Hydreon rain sensor setup.

CloudWatcher advantages:

(*) Find here the pice list of the REPAIRS AND SPARE PARTS for the AAG CloudWatcher.

The CloudWatcher includes:

  • custom box with a special exterior finish that includes:
        • Clouds sensor
        • Connection to Hydreon Rain sensor (sold separately) (1)
        • Light sensor capable of measuring the sky darkness quality – New 2022/2023
        • Dichroic UV/IR filter for the correct measurement of the sky darkness quality – New for 2022/2023
        • Temperature sensor
        • Relative Humidity, Atmospheric pressure sensor and Temperature sensor (RH & AP version)
        • Anemometer (optional external accessory)
  • Long weather-proof cable (several lengths) with IP68 connector
  • Relay for observatory opening/closing

    Graphic of the dichroic UV/IR filter which covers the new light sensor

(1) Please note, the RG-9 rain sensor does not distinguish condensation from rain, so we do not recommend it in high humidity environments.

Let’s see them in detail:

► The CloudWatcher box. All the data collected by the AAG sensors and the anemometer are reflected in the computer through their corresponding graphics. These allow a comprehensive and easily understandable measurement of atmospheric conditions:

Clouds sensor 

Through an infrared sensor of the AAG CloudWatcher measures the temperature of the sky, and an electronic thermometer measures the internal temperature. Both data are then related by a powerful formula used to determine the existence of clouds. The measuring result is easily read on the graphic “Cloud”.

Unlike other detectors, the AAG CloudWatcher allows the user to set the parameters for measurement, and thus adjust the detection of clouds for each place.

Rain sensor (requires the Hydreon Rain sensor, sold separately)

Connected to HRG-9 Hydreon Rain sensor, the CloudWatcher rain graph will display 3 different levels for:

  • dry,
  • rain, and
  • failure (disconnection).
Light sensor

From 2022 and 2023 the CloudWatcher incorporates a new extremely sensitive light sensor capable of not only distinguishing day and night, but also measuring the brightness of the background sky in “MPSA” (magnitudes per square arc second). Follow us in the forum for further information.

Temperature sensor

Responsible for measuring the ambient temperature.

Relative Humidity, Atmospheric pressure sensor and Temperature sensor (RH & AP version)
The data from this sensor are supported by the SOLO CW (attached image).

If you want to take a look at our SOLO installed in Hamilton, New Zealand, click here:

Windows program displays the value in the screen, with the dew point, and the data are included in the “Single line data” file (*).

Anemometer (OPTIONAL)

Shows the wind speed.

►The CloudWatcher cable connects the device to a PC and it is available in 4 lengths: 3, 5, 7, or 10m. (From 2018/November you also can get the CloudWatcher without cable).

It has a special weather-proof connector, IP68, which allows the easy and comfortable installation of the unit. The cable can be routed conveniently through a conduit, the thicker part of it is only 19mm in diameter.

IP68 Weipu connectors for power cable and anemometer
IP68 Weipu connectors for power cable and anemometer


Relay (1) for observatory opening/closing, can withstand a voltage of 220 V. But not being a security cable it is advised to connect it to low voltage devices (12 or 24V).

Technical specifications:

  • Power 12 or 15V, current < 1 A
  • Standard 5.5 / 2.1mm jack, center positive
  • RS232 Serial port (**)
  • Weight:
    • 160gr. (no RH & AP version)
    • 185gr. (RH & AP version)
  • Size:
    • 130*85*45 mm. (no RH & AP version)
    • 130*85*60 mm. (RH & AP version)

(**) USB to RS232 adapter available here.

In addition, the CloudWatcher software incorporates advanced features such as:

  • Multiple users in LAN (MASTER mode and REMOTE mode operation);
  • MASTER and REMOTE installations can be independently parameterized;
  • Sky temperature correction model to account for excessive atmospheric longwave radiation during summer;
  • All alerts can be defined as sound alerts, with a specific sound file to be played when the alert condition occurs;
  • Switch control can be disabled and be performed by an external program (suitable to control other equipment);
  • Allows the electrical constants to be changed by the user;
  • A complete set of properties/methods for inter-program communications;
  • Compatible with existing firmware versions 1.xx, 2.xx and future version 3.xx;
  • ACP, Sequence Generator+, CCDCommander, CCDAutopilot, Prism, CCDAutoPilot, and Maxpilote compatible; plus any ASCOM-compliant software.
  • With the program, AAG WeatherCentre (***) can combine information from any standard weather station supported by Virtual Weather Station, Weather Display, or Cumulus software.
  • Several free programs for mobile devices, for example, the one developed by Francisco Jesús Cortés to allow you to receive an alarm on your mobile phone.

(***) The program AAG WeatherCentre is no longer needed since 2017 because the AAGCloudWatcher measures wind speed and relative humidity. It is fully operational but not being updated – offered “as is”.

AAG CloudWatcher con anemómetro montado




CloudWatcher documentation:


Cable length

10m. cable, 3m. cable, 5m. cable, 7m. cable, Without cable

Relative humidity and Atmospheric pressure sensor

With RH & AP sensor, Without RH & AP sensor

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