Encircled Energy
The English name Encircled Energy ( EE ), in German about energy on a circular area , is a name from astrophotography.
High-resolution telescopes fold the image of point light sources with the device-specific point spread function (PSF). On the one hand, the entire light energy of a diffraction disk should be recorded. On the other hand, the detector area must be small enough to be able to separate overlapping diffraction disks of two stars. EE indicates what proportion of the total received energy is available for detection. The term Ensquared Energy refers to a square area instead of a circular one, as it is given for example by CCD pixels.