Sky Temperature Monitor is an IR based instrument for measuring sky transparency during the observing or imaging session. It measures the apparent Sky temperature by extrapolating from observed emissivity. Since water vapor is a heavy absorber in mid-IR range, any clouds or even the atmospheric vapor will have profound effect on the readings.

The instrument should be mounted to the front of the OTA, pointing towards what the telescope is observing. Its narrow, 5 degree, field of view will ensure that the observed area is in very close vicinity of telescopic FOV. In the event that a cloud starts to encroach towards the observed area, it will become very evident by observing the IR measured temperature and the standard deviation charts.

In addition, by observing the magnitude of the Sky temperature variance it is possible to gage the seeing and track its changes in real time: Since seeing is produced by the inhomogeneities of the real part of the air’s dielectric, and since both temperature and water vapor density affect this parameter, we would expect that the variability of the Sky  mid-IR temperature would correlate with the low-altitude component of the atmospheric seeing.


  • Sky Temperature and Sky Delta to detects even smallest cloud whiffs
  • Atmospheric Perceptible Water column in mm
  • Ambient parameters such as Temperature, %RH and Dew Point
  • Dew Point Alarm
  • USB and Wi-Fi Connectivity
  • ASCOM drivers for supported readings
  • Native monitoring application for all encompassing data monitoring
  • USB Powered
STM (Sky Temperature)    
Range -70 to 60 degrees C
Resolution 0.01 degrees C
Noise 0.01 degrees C RMS
Beamwidth (HWHM) 5 degrees
Accuracy TBD degrees C
Update Rate 1 sec
Emmisivity 0.7 set to typical Sky
PWV 0 to 20 mm (reduced accy. Above 20mm)
Measured Ambient    
Temperature -20 to 70 degrees C
RH 0 – 99.9 %
DP -20 to 70 degrees C
Protocol 802.11 b/g/n 2.4 GHz
RF Power 100 mW
Protocol USB 2.0  
Connector Micro B