Schmidt–Newtonian telescope

The resulting system has less coma and diffraction effects than a Newtonian telescope with a parabolic mirror (which is free of spherical aberration but not free of coma) and a "spider" secondary mirror support.

[1] The design uses a 45° flat secondary mirror to view the image, as in a standard Newtonian telescope.

The corrector plate also helps to seal the tube assembly from air currents, and provides mounting point for the diagonal mirror, eliminating the diffraction effects from a "spider" secondary support.

The all-spherical surfaces are much easier to manufacture, especially in short focal ratios.

Telescopes using this design typically have a short focal ratio of around f/4, making them well suited for astrophotography or CCD imaging.