Herschelian telescope Herschelian telescope /hɝːˈʃɛliən ˈtɛləˌskoʊp/

noun

1. A reflecting telescope with the mirror slightly tilted to throw the image to the side where it can be viewed  ( Herschelian telescope , off-axis reflector )
   a reflecting telescope with the mirror slightly tilted to throw the image to the side where it can be viewed