© 2006 Centro Astronómico Hispano-Alemán A.I.E
Cloud Sensor Information
The cloud sensor senses how clear the sky is (the amount of clouds) in an indirect manner. It measures the sky
temperature by sensing the infrared radiation in the 8 to 14 micron wavelengh range. Then it reads the ambient
temperature and compares it against the sky one. This difference between both temperatures is the value you can
read on the main weather page. As this difference is reducing, more clouds are on the sky. With a fully overcast
sky with low clouds or fog, usually both temperatures are very similar, so the difference is reduced to a minimum.
You can see on the next table the actual values we are using:
|Cloud Sensor calibration values|
|Mainly clear||       Less than -28.0 |
|Few clouds or high clouds|| between -28.0 and -24.0 |
|Some clouds|| between -24.0 and -19.0 |
|Mainly cloudy|| between -19.0 and -17.0 |
|Very cloudy|| between -17.0 and -14.0 |
|Overcast or fog||       Higher than -14.0 |
Together with the clouds information, the sensor is telling us also about the rain/snow.