Amici prisms 90°

An Amici prism directs the light path inside a telescope and inverts the image to create a comfortable observing position. This image inversion feature distinguishes the Amici prism from a zenith mirror. With the Amici prism, the image is no longer upside down, so that the telescope can be used for observing nature. An Amici prism also makes orientation easier when observing the Moon.

Amici prisms are only useful for lens telescopes (refractors), Schmidt-Cassegrain and Maksutov telescopes. An erecting lens is required for a Newtonian telescope.