Well, it's happened to us! To fight back, Boltwood Systems Corporation has developed and built a new tool for the astronomer's arsenal.

The Boltwood Cloud Sensor II measures the amount of cloud cover by comparing the temperature of the sky to the ambient ground level temperature. The sky temperature is determined by measuring the amount of radiation in the 8 to 14 micron infrared band. A large difference indicates clear skies, whereas a small difference indicates dense, low-level clouds. This allows the sensor to continuously monitor the clarity of the skies, and to trigger appropriate alerts on your computer.

The device also includes a moisture sensor which detects rain and snow. To prevent false alarms due to frost or dew, a heater keeps the sensor slightly above ambient temperature. When rain or snow falls, the sensor is automatically heated to 70 degrees Celsius. This clears the sensor quickly when the precipitation ends, and ensures that the sky-measuring thermopile has a clear view.

New! The Boltwood Cloud Sensor II now measures wind speed, using a specially-designed anemometer with no moving parts. The sensor will now warn you when winds speeds are too high for safe operation of the observatory. The sensor also now measures humidity, and provides a continuous readout of temperature, humidity, and dew point.

The included Clarity II Windows software monitors the sensor via a USB interface. It displays and logs all sensor information. Alerts can appear visually, or with sounds from either the PC speaker or sound card. The user can choose to be alerted for clouds, wind, and/or wetness; all with adjustable thresholds. You can display a mini status window or the full information display.

The sensor unit itself will trigger an electrical contact closure when heavy clouds, high winds, or precipitation is detected. When connected to a dome or roof controller, this contact can be used to trigger closure even if the computer is not operating. This provides a 'last line of defence' against damage to your observatory equipment.

ActiveX and file interfaces are provided for integrating the Clarity II software into your observatory control system.

The software is indicating a clear sky. Winds are light, the temperature is near freezing, and the humidity is high; but we are not near the dew point and the sensor heater is not running.

Clouds have just rolled in. The roof closure contacts have been activated to protect the observatory. No sign of rain yet, but the moisture detector will see the very first drop.