Measurement of sky quality based on the analysis of the image of the AllSky camera
Actualizado: 2 de abr de 2020
The images that the AllSky camera captures are a great help to know the current state of the sky. Being the camera in color we can observe the state of the sky with the same clarity as when we look up and we get an idea of whether it is worthwhile or not to put the telescope to work. The color also gives us relief and allows us to determine the type of clouds at nightfall. We can also determine by color of the image if the urban lighting has been turned on.
The image on the right captured with the AllSky camera shows a cloudy sky with an opening at the zenith.
In addition to the information that gives us the visual analysis of the image, we can go a step further and with a simple computer processing we can obtain a measure of the darkness of the night sky.
I have added on the web the description of a method that complements other solutions based on measuring the temperature of the sky or the level of light received. A simple software interrogates the camera to obtain average levels of the basic colors and processes the information to represent the level of darkness. The method could be summarized by saying that we measure the blue average of the image weighted with the level of exposure.