Fig. 1
Left panel: distribution of the sample sources on the sky. The vast majority of sources was taken at zenith distances below 60° (≡airmass <2.0). Right panel: source distribution on the celestial sphere in Eckert-Greifendorff projection. The sources are fairly homogeneously distributed with only a slight enhancement towards the Galactic plane. The Galactic centre is marked with a circle.
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