Q&A
  • What is the "Kidney Bean Effect"?
  • Add on Sept. 28, 2011, 1:26 a.m.

The "Kidney Bean Effect" is not the same phenomenon as the before mentioned "black spot". In some long f.l or wide angle eyepieces, it is sometimes necessary to move the eye closer to the eyepiece in order to see the edge of the field. Sometimes, when this occurs, parts of the field between the centre and the edge are cut off, as part of the quickly converging beam misses the eye's pupil. This appears to the observer as a giant kidney bean shaped dark region that meandors around the field as head moves.