Herschel-Cassegrain telescope

Herschel-Cassegrain telescope

[′hər·shəl ′kas·gran ‚tel·ə‚skōp]
(optics)
A modification of a Cassegrain telescope in which the primary paraboloidal mirror is slightly inclined to the optical axis, and both the secondary hyperboloidal mirror and the eyepiece are located off the axis, so that it is not necessary to pierce the primary.