SQM 11

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SQM Data
06-05-27
Granger, Indiana, mid-driveway 
Clear Sky Clock (below): PHM Planetarium
11:22 p.m. EDT to 11:55 p.m. EDT
clear, subtle haze
Note: meter readings were not in sequential order from 730 to 740.

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Meter # 730 731 732 733 734 735 736 737 738 739 740
                       
  19.20 19.16 19.17 19.20 19.14 19.03 19.13 19.21 19.10 19.08 19.14
  19.20 19.15 19.16 19.21 19.22 19.09 19.06 19.26 19.10 19.05 19.12
  19.19 19.17 19.13 19.24 19.23 19.14 19.04 19.25 19.14 19.08 19.18
  19.22 19.17 19.08 19.20 19.31 19.13 19.06 19.27 19.11 19.21 19.20
  19.20 19.14 19.12 19.22 19.09 19.13 19.15 19.24 19.12 19.15 19.12
  19.21 19.20 19.10 19.20 19.15 19.08 19.15 19.23 19.12 19.13 19.17
  19.24 19.20 19.09 19.27 19.13 19.17 19.17 19.24 19.10 19.13 19.15
  19.18 19.18 19.10 19.17 19.19 19.14 19.12 19.24 19.11 19.12 19.21
  19.19 19.17 19.12 19.20 19.16 19.16 19.16 19.21 19.11 19.13 19.18
  19.20 19.17 19.06 19.19 19.20 19.15 19.15 19.16 19.11 19.12 19.16
  19.22 19.17 19.13 19.18 19.20 19.14 19.14 19.23 19.07 19.12 19.18
  19.22 19.15 19.16 19.24 19.16 19.11 19.15 19.27 19.08 19.16 19.18
  19.23 19.17 19.03 19.23 19.17 19.11 19.09 19.25 19.08 19.17 19.18
  19.24 19.17 19.06 19.22 19.22 19.15 19.07 19.27 19.09 19.12 19.19
  19.18 19.18 19.10 19.21 19.21 19.16 19.17 19.27 19.10 19.12 19.12
  19.21 19.18 19.12 19.25 19.16 19.11 19.12 19.24 19.11 19.15 19.11
  19.21 19.19 19.10 19.23 19.16 19.16 19.13 19.27 19.09 19.11  
    19.18 19.12 19.21 19.20 19.11 19.02 19.27 19.13    
    19.19 19.12 19.23 19.25 19.13 19.07 19.19 19.11    
    19.17 19.12   19.25 19.24 19.15 19.24 19.11    
      19.13   19.22 19.23 19.15 19.24 19.12    
          19.22 19.12          
                       
Average 19.21 19.17 19.11 19.22 19.19 19.14
19.12
19.24 19.11 19.13 19.16
Combined Average 19.17

Clear Sky Clock data courtesy of A. Danko; used with permission.

SQM Data
06-05-28
Stevensville, Michigan, backyard
Clear Sky Clock (below): Warren Dunes State Park
11:31 p.m. EDT
clear, no moon, astronomical twilight~11:15 p.m.
SQM readings by Kathleen R.
Note: meter readings were not taken in sequential order from 730 to 740.  Number 731 was early, while 731 was repeated about 20 minutes later as 731b.  

Meter # 730 731 732 733 734 735 736 737 738 739 740   731b
                         
  19.89 19.87 19.86 20.13 19.95 19.80 19.89 20.07 19.93 19.82 19.93   19.93
  19.88 19.84 19.86 20.11 19.88 19.74 19.85 19.98 19.94 19.86 19.87   19.90
  19.88 19.84 19.81 20.10 19.88 19.78 19.85 19.99 19.93 19.86 19.87   19.92
  19.90 19.83 19.86 20.11 19.89 19.78 19.85 19.98 19.94 19.82 19.86   19.92
  19.89 19.83 19.86 20.11 19.89 19.73 19.85 19.99 19.93 19.80 19.85   19.92
  19.88 19.84 19.85 20.11 19.89 19.72 19.86 19.98 19.93 19.82 19.86   19.91
  19.89 19.84 19.79 20.10 19.90 19.72 19.86 19.99 19.94 19.82 19.85   19.90
  19.88 19.84 19.82 20.10 19.89 19.74 19.86 19.97 19.93 19.86 19.85   19.92
  19.91 19.84 19.83 20.10 19.90 19.73 19.85 19.96 19.93 19.8 19.85   19.92
  19.90 19.84 19.85 20.11 19.95 19.75 19.85 19.98 19.92 19.82 19.85   19.91
  19.91 19.85 19.85 20.10 19.93 19.78 19.86 19.98 19.93 19.81 19.85   19.91
  19.88 19.85 19.86 20.10 19.90 19.72 19.85 20.04 19.92 19.82 19.91   19.92
  19.91 19.84   20.10 19.90   19.85 19.99 19.92 19.88 19.83   19.92
  19.90 19.85   20.10 19.89   19.86 19.97 19.92 19.83 19.81   19.92
        20.11 19.89   19.85 20.00 19.92 19.83 19.81   19.92
          19.89     20.04 19.94       19.90
                19.97 19.93       19.92
                20.01         19.90
                         
Average 19.89 19.84 19.84 20.11 19.9 19.75 19.86 19.99 19.93 19.83 19.86   19.91
Combined Average 19.89

Clear Sky Clock data courtesy of A. Danko; used with permission.

 

From the PHM Clear Sky Clock at http://cleardarksky.com/c/PnnHrMPINkey.html: 

Darkness
-4 -3 -2 -1 0 1.0 2.0 3.0 3.5 4.0 4.5 5.0 5.2 5.4 5.6 5.8 6.0
The line labeled darkness is not a weather forecast. It shows when the sky will be dark, assuming no light pollution and a clear sky. Black is a dark sky. Deep blue shows interference from moonlight. Light blue is full moon. Turquoise is twilight. Yellow is dusk and white is daylight. For those who prefer numbers, the scale is also calibrated. The numbers are the visual limiting magnitude at the zenith. (The brightness of the faintest star a standard observer can see straight up.) Mouse over a darkness block for details.

It is based on Ben Sugarman's Limiting Magnitude calculations page. It takes into account the sun's and moon's position, moon phase, solar cycle and contains a scattering model of the atmosphere. It doesn't consider light pollution, dust, clouds, snow cover or the observer's visual acuity. So your actual limiting magnitude will often be different.

A. Danko, creator of the Clear Sky Clock, writes:

"Accurate SQM readings should be had only when the clock's darkness line reads 6.0...The darkness line calculates a theoretical sky brightness that does not consider light pollution. But it does consider the phase of the moon, altitude of the moon and altitude of the sun...It clearly shows that even a gibbous moon can have very little effect when it is at only a few degrees altitude. The altitude at which a given phase of the moon affects the brightness at zenith varies in a complex way which the darkness model takes into account...While the 6.0 number the "darkness" line calculates for a sky free of scattered moonlight and sunlight is not quite right (mostly because vision varies hugely from person to person), it's a very good indication of when the sky will be at minimum brightness from light from the sun and moon."    (Copyright ©2006 A. Danko; used with permission.)

 

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