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pyobs allsky cloudcover

Build Tests

This module analyzes Allsky images for cloud cover and writes the (zenith) cloud fraction and cloud change into an Influx DB. It also includes a web service to query celestial positions for the limiting magnitude, which is calculated in an intermediate step.

Best paired with: pyobs-allsky

How does it work?

The module listens for a new image from the configured camera. If a new image has been captured, an image analysis pipeline is run on the image, depending on the solar altitude when the image was captured. Currently there is only a "night" pipeline, which works best after astronomical twilight (solar altitude below -18°). This pipeline estimates the limiting magnitude of each pixel based on the visibility of the stars. Pixels are considered cloudy if their limiting magnitude falls below a defined threshold.

Web Service

Point Query

Returns the cloudiness value of the analyzed sky position closest to the requested position.
Routes:
/query/point?ra={Right ascension in degree}&dec={Declination in degree} or
/query/point?alt={Altitude in degree}&az={Azimuth in degree}

Example:
/query/point?alt=90.0&az=0.0

Result:

Field Type Description
obs_time float Observation Unix time of the last analyzed image
value bool If it is cloudy at the requested point

Area Query

Returns the cloud fraction within the requested great circle.

Routes:
/query/area?ra={Right ascension in degree}&dec={Declination in degree}&radius={Radius in degree} or
/query/area?alt={Altitude in degree}&az={Azimuth in degree}&radius={Radius in degree}

Example:
/query/area?alt=90.0&az=0.0&radius=10.0

Result:

Field Type Description
obs_time float Observation Unix time of the last analyzed image
value float Cloud fraction in the requested area in percent

Configuration

See example.yaml