Lick Weather

Lick Weather Explanation

The data are collected by the computer at the Katzman Automated Imaging telescope at Lick Observatory, located near the water tanks on the high hill East of the Three Meter Telescope dome. weather station The weather is collected every half hour and about 38 entries are kept. The entry time is in Unversal time.


Measures the temperature of the telescope frame (indoor) in degrees Celsius. The calibration is good to about +/- 1.0C.

A second sensor measures the outside air temperature (OAT) in a white box mounted on the East side of the dome. The sun make strike the box at certain times of the day and therefore the sensor may not reflect the true air temperature.


The Vaisala electronic humidity gauge is mounted on the East side of the dome. It currently reads about 15% high. The units are percent Relative Humidity. It is mounted in the louvered housing shown on the photo to the right.

Windspeed and Direction

The wind information is derived from the indicators atop the water tank. These are the same ones that are telemetered to the 3m dome on the Bendix readouts. The accuracy is the same as the meter readouts. The integration time is about 1 second.

North is defined as 0 degrees East is 90.0. The wind speed is in mph.

IR 'cloud' detector

An infrared thermopile Model 2M made by Dexter Research sensitive to the 8-14 micron region is pointed at a ~30 degree wide field to the East of zenith. The detector is inside the grey box at the top of the photo shown to the right. It measures the cloud temperature. (1/8/97) current calibration is: They have been converted to a linear 'cloud' scaling of 1 for overcast and 0 for clear. The scaling values will change. The sensor can become covered with frost or dew and give false cloudy readings.


The Vaisala DRD11A rain sensor returns the value 1 when wet and 0 when dry.


Is a misnomer, it is the analog indication of the rain sensor and is 3.0 minus the output volts from the sensor. The reading of 0 therefore is totally dry and increasing values indicate more water.

Last Updated June 2, 2000