Diagonal mirrors

Erecting lenses are available as zenith mirrors, zenith prisms or Amici prisms. The latter are useful for terrestrial observation and are therefore also available with a flatter deflection angle of 45°.

• Without an erecting lens, the image in the telescope depicts north below and east to the right.
• With zenith mirrors and zenith prisms, the telescope depicts a laterally transposed image: north is at the top, east is at the right and, without tracking, stars wander to the left.
• Amici prisms show a correct image as it would be seen with the naked eye. Therefore, these prisms are essential for nature-watching. However, their more complicated construction makes them susceptible to image defects, which is why the laterally transposed image is preferred in astronomy.

Most erecting lenses have simple plug-in connectors, as is common seen with eyepieces. For SC telescopes, however, there are also models with screw threads.