What type of telescope features a convex secondary mirror?

A Cassegrain reflector telescope utilizes a combination of mirrors, including a primary concave mirror and a secondary convex mirror. The secondary mirror is strategically placed to reflect light gathered by the primary mirror down through a hole in the center of the primary mirror, allowing for a more compact design. This setup enhances the telescope's focal length without increasing its overall physical size, making it ideal for astronomical observations where space and portability are concerned. The use of a convex secondary mirror is essential in this design as it helps to focus the light more effectively, which is why the Cassegrain reflector is often favored in professional and amateur astronomy alike.

In contrast, a Newtonian reflector does not have a secondary mirror that is convex; instead, it uses a flat secondary mirror to redirect light. A refractor telescope relies entirely on lenses rather than mirrors, eliminating the presence of a secondary mirror altogether. Catadioptric telescopes combine lenses and mirrors, but they may not specifically use a convex secondary mirror in the same manner as the Cassegrain design. Thus, the characteristics and design of the Cassegrain telescope clearly define its unique use of a convex secondary mirror.