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.
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. Plus the sensor now detects daylight and can be set to automatically close the roof to prevent any possibility of sunlight entering the telescope. The sensor now also 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. The computer display can be set for a mini status window or a 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. The thresholds for roof closure are set through the Clarity software.
Cloud Sensor Graph II software is now included. This provides a continuous graphical plot of the sky conditions, temperature, wind, humidity, etc.
ActiveX and file interfaces are provided for integrating the Clarity II software into your observatory control system.
The complete package, shown above, includes sensor with mounting bracket (shown attached to a pole), cable, adapter box, universal AC power supply with international plugs, USB cable, protective cover, and PC software.
Available exclusively through Diffraction Limited, the Boltwood Cloud Sensor package includes the sensor unit, mounting bracket, a 50-, 100- or 150-foot (15m, 30m or 45m) data cable, 110/220 VAC 50/60 Hz power supply adapter, and software CD-ROM. Compatible with Windows 2000/XP. Open source Linux drivers are available.