Indicators

  Close Criteria  

  Open/Reopen Criteria  

Wind

• Hand held anemometer
  
• X-met Readings (currently not available)
  
• Other Mauna Kea Weather Station Readings
  

• Sustained wind speed of 45mph
  
• Sustained wind of 25mph or greater AND moderate dust accumulation
  

• Sustained wind of 40mph or less for at least 30 minutes
  
• Wind Gusts less than 45mph
  
• Minimal dust accumulation after 30 minute buildup test
  
• No other adverse weather condition
  

Windchill (Laser Spotters only)

• Wind Chill Charts by Bob found here

• Wind chill < -15 degrees C
  

• Wind Chill rises above limit

Fog

• Verbal warning from other observatories
  
• Direct sighting
  
• Sudden jump in Dewpoint
  
• X-Met warning lights
  

• Fog sighted within 200m of telescope
  
• Fog sighted within 400m of telescope AND within 15 minutes of contact
  
• Dewpoint reading sustained within 2 degrees C or less of any of the outside temperature, secondary temperature, or primary mirror temperature for 5 minutes.
  
• Condensation on outside surfaces
  

• Dewpoint differential increases to more than 2 degrees C with respect to the outside temperature, secondary temperature, or primary mirror temperature and stays there for at least 20 minutes
  
• No visible fog or clouds within 400m radius of domes
  
• No low overhead clouds within 1/2 mile radius of summit
  
• No other adverse weather condition

Precipitation

• Visible sighting of precipitation in the atmosphere (e.g., snow, rain, sleet, etc.)
  

• Visible sighting of precipitation in the atmosphere (e.g., snow, rain, sleet, etc.)
  
• Stratus or Cumulus type clouds sighted overhead of the domes
  

• Dewpoint differential increases to more than 2 degrees C with respect to the outside temperature, secondary temperature, or primary mirror temperature and stays there for at least 30 minutes
  
• No low overhead clouds within 1/2 mile of summit
  
• No other adverse weather conditions
  
• No significant buildup of snow/ice on dome shutters
  

High Clouds

• Visible sighting of clouds above or around summit
  
• Satellite image of clouds above summit
  

• Precipitation producing (Stratus or Cumulus) clouds sighted overhead of the domes
  
• Cloud cover exceeding 6 magnitudes of extinction AND sky conditions which preclude primary observing program
  

Ice/Snow on Dome

• Accumulation of ice or snow on domes as reported by inspectors (usually daycrew)
  
• Accumulation of ice on surfaces around building
  

• Snow and ice falls into dome upon opening attempt
  

• Winds sustained below 10 mph and no infalling material upon opening of shutters
  

Condensation

• Saturated Air (Dewpoint reading sustained within 2 degrees C or less of any of the outside temperature, secondary temperature, or primary mirror temperature for 5 minutes)
  
• Condensation (liquid or solid) forming on outside surfaces
  

• >Dewpoint reading sustained within 2 degrees C or less of any of the outside temperature, secondary temperature, or primary mirror temperature for 5 minutes.
  
• Condensation forming on outside surfaces
  

• Dewpoint differential increases to more than 2 degrees C with respect to the outside temperature, secondary temperature, or primary mirror temperature and stays there for at least 30 minutes AND no buildup of solid or liquid condensation on outside surfaces after 30 minutes