Seeing can be rated as follows: (consider a high power
view - 30-40X/inch)
I - Boiling image without any sign of diffraction
pattern.
II - Important eddy streams in the central disc. Missing
or partly missing diffraction rings.
III - Central disc deformations. Broken diffraction
rings.
IV - Light undulations across diffraction rings.
V - Perfect motionless diffraction pattern.
