A strip of glass or other transparent material whose light transmission decreases evenly from one end to the other. The change in light transmission is accomplished by applying a coating whose thickness increases along the wedge, or by an increase in photographic density. The wedge is used at the eyepiece to reduce the intensity of a star in the field of view until it appears the same brightness as another, fainter, comparison star. The magnitude difference between the stars can then be measured.
Subjects: Astronomy and Astrophysics.