Automated Weather Monitoring for Observatories: Lunatico AAG CloudWatcher Review

I had always been interested in cloud detectors for my imaging sessions, but since most of my imaging is done from my backyard (semi-remote), I figured a cloud detector wasn’t needed since I can “see” the sky conditions myself.

But after a few months of using the AAG CloudWatcher made by Lunatico, I now see the advantages of having one. I’ll be sharing my experience with it here.

The AAG CloudWatcher. Credit: Rouzbeh Bidshahri

Hardware & installation

Installation of the AAG CloudWatcher is easy. Just attach it to the side of your observatory, fence, post, or anything else convenient.

The AAG CloudWatcher consists of a plastic box with sensors on the side that faces the sky. Sensors include a cloud detector, rain sensor, light sensor, and, optionally, a wind speed anemometer.

The CloudWatcher installed on the author’s observatory. Credit: Rouzbeh Bidshahri

The version I have has the relative humidity and atmospheric pressure sensors on the bottom, an option definitely worth the extra $65.

Only one cable is needed, with lengths available 3m to 10m, with the other end having:

    • 12v power input jack
    • RS232 serial port (for USB, you’ll need an RS232 serial-to-USB adapter)
    • Relay: A pair of wires that act as a relay switch for (optionally) sending commands to devices like roof opening/closing motors.

Rain Sensor Options

There are two options for rain detection.

The two different types of rain sensors. Credit: Rouzbeh Bidshahri

1 – Capacitive sensor

Capacitive sensor advantages:

    • Integrated into the CloudWatcher box
    • Stronger heater, so it can work with snow and heavy dew (tested with good results)
    • Can indicate the approximate amount of rain

Capacitive sensor disadvantages:

    • Needs to be kept relatively clean (bird droppings, etc.)
    • Sensing surface could be scratched
    • Calibration needed (2 minutes)

2- Hydreon RG-9 Sensor

This rain sensor uses infrared LEDs and a transparent dome-shaped plastic lens to detect rainfall ($70 option).

Hydreon RG-9 Sensor Advantages:

    • Rugged and maintenance free
    • Transparent dome can be replaced, if needed
    • No calibration needed

Hydreon RG-9 Sensor Disadvantages:

    • Weak heater, so it won’t work well in snow
    • Not quantitative (Indicates only rain or no rain)
    • Moving shadows (leaves, anemometer) can mislead the sensor
Hydreon RG-9 Sensor. Credit: Rouzbeh Bidshahri

I have both sensors and I feel that provides the best of both worlds. The built-in capacitive sensor detects whatever threshold I consider unsafe (set in the software, described below) and closes the shutter or stops imaging. I like that it shows a value even with a single drop of water, before it really starts to rain.

The Hydreon sensor can be connected to the CloudWatcher, but mine was wired to my dome motor (the Lunatico Beaver) so it will trigger shutter closure even if no software or PC is present. This redundancy gives me extra peace of mind.

Wind Speed Sensor (Anemometer)

Lunatico also offer a wind speed sensor that connected to the CloudWatcher device ($145). I don’t have this sensor but I may try it later.

Anemometer. Credit: Lunatico


The software is straightforward and, while the user graphic interface isn’t aesthetically pleasing, it’s simple and gets the job fine. It was easy to install and understand.

The AAG CloudWatcher connects to a computer where the current sensor readings are displayed in the main panel, including environmental conditions such as temperature, relative humidity, sky brightness (darkness), wind speed and the presence of clouds or rain.

There is an optional standalone device – the SOLO – that eliminates the need for a PC and provides the readings over a network (the SOLO will be reviewed later).

AAG CloudWatcher main sensor readout tab. Credit: Rouzbeh Bidshahri

Thresholds can be set for the levels of each parameter, such as defining what constitutes clear, cloudy, or overcast, and graph them against time. This provides a visual representation of ambient conditions.

Limits and thresholds settings. Credit: Rouzbeh Bidshahri

Cloud Sensor

The CloudWatcher’s main feature, detecting clouds, uses an infrared sensor and the temperature of the sky to detect the presence or absence of clouds. The measurement algorithm parameters can be tweaked by the user. I have found it to be accurate and responsive.

Cloud coverage graphic presentation. Credit: Rouzbeh Bidshahri

Temperature & Humidity

Below is an example of a rise in humidity detected by the CloudWatcher, allowing the user to take measures to avoid the formation of dew on the optics.

Similarly, ambient temperature changes are useful for monitoring things like temperature acclimatization inside the observatory compared to outside for telescope refocusing routine schedules.

Graphic humidity presentation. Credit: Rouzbeh Bidshahri

The rain sensor is essential for safety, helping avoid potentially catastrophic situations such as a sudden shower that can damage the exposed equipment. Below is a real-life example from our backyard, showing how conditions can change from completely dry to heavy rain within minutes. In this case, the CloudWatcher triggered a dome shutter closure.

Sudden rain detected at the author’s observatory. Credit: Rouzbeh Bidshahri

Light Sensor

The light sensor has been useful for timing the start and end of data acquisition, down to the minute. Astronomical darkness varies in latitude and throughout the year. I find the sensor to be far more accurate than simply peeking out the window or using an all-sky camera.

Light sensor indicating sunrise. Credit: Rouzbeh Bidshahri

Wind Speed

The optional anemometer measures wind speed, allowing those in windy locations to shut down a session (automatically or manually) should wind speeds reach dangerous levels.

Wind speed graph. Credit: Lunatico

ASCOM Safety Monitor

This is something I really needed for my nightlong autonomous imaging sessions – a Go/No-Go switch using “Safe” and “Unsafe” conditions.

The user defines conditions for what to consider unsafe. The thresholds for each are adjustable. I selected “Overcast” or “Rain” or “Very Light” as “Unsafe”:

User selection tab for defining “Unsafe” conditions. Credit: Rouzbeh Bidshahri

My imaging software, N.I.N.A., along with any other ASCOM-compliant imaging software, connects to the ASCOM Safety Monitor. Automatic imaging sequences continue to loop until an “Unsafe” command from the Safety Monitor triggers a shutdown.

For example, once clouds reach the “Overcast” level that I selected, indicating that rain may be imminent, the safety monitor switches to “Unsafe” and imaging stops. I program N.I.N.A. to terminate the session and close the observatory roof once an unsafe condition is detected. This process is independent of the Hydreon rain sensor that is hardwired to the dome motor, which can also trigger an unsafe condition.

ASCOM integration with N.I.N.A. imaging software. Credit: Rouzbeh Bidshahri

Final thoughts

The AAG CloudWatcher has been running nonstop on my observatory for several months and has been working well without any input from me. Having a clear picture of the weather conditions, I feel a lot more confident about my equipment being exposed to the elements.

The main advantage to me is the ASCOM integration, meaning my autonomous imaging sessions are much safer now.

I initially considered a CloudWatcher to be a “nice to have” accessory. Now, I feel I’d be flying blind without the weather conditions being monitored continuously.


    • Lots of sensors and features
    • Cloud detection works well
    • The user can select what is or isn’t required
    • Reasonably priced


    • Software interface doesn’t look very appealing (though this doesn’t affect operation)

MSRP: $365 to $480



NOTE: Rouzbeh Bidshahri’s review of the Lunatico Solo, a standalone computer for the CloudWatcher, will be published on Saturday, April 9.

About Rouzbeh Bidshahri

Rouzbeh Bidshahri is a mechanical engineer with a lifelong passion for astrophotography. He has tested dozens of telescopes ranging from 3 to 20 inches in aperture and has spent several years optimizing systems for very high-resolution planetary imaging in the sub 0.1 arcsecond/pixel range. He has contributed to several institutions such as ALPO (The Association of Lunar and Planetary Observers). His main area of interest has been designing and operating larger setups, and he is currently focusing on high resolution, long exposure photography for both broadband and narrowband deep sky imaging.

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