Optical telescope
Many types of telescope fold or divert the optical path with secondary or tertiary mirrors. These may be integral part of the optical design (Newtonian telescope, Cassegrain reflector or similar types), or may simply be used to place the eyepiece or detector at a more convenient position. Telescope designs may also use specially designed additional lenses or mirrors to improve image quality over a larger field of view. 
Design specifications relate to the characteristics of the telescope and how it performs optically. Several properties of the specifications may change with the equipment or accessories used with the telescope; such as Barlow lenses, star diagonals and eyepieces. These interchangeable accessories don't alter the specifications of the telescope, however they alter the way the telescopes properties function, typically magnification, apparent field of view and FOV.
3.67 m Advanced Electro Optical System Telescope
The 3.67-meter telescope, known as the Advanced Electro-Optical System (AEOS), owned by the Department of Defense, is the United States' largest optical telescope designed for tracking satellites. The 75-ton AEOS telescope points and tracks very accurately, yet is fast enough to track both low-Earth satellites and ballistic missiles. It can slew at nearly 20 degrees per second. It is an f/200 and has an extremely narrow field of view. AEOS can be used simultaneously by many groups or institutions because its light can be channeled through a series of mirrors to seven independent coudé rooms below the telescope. Employing sophisticated sensors that include an adaptive optics system, radiometer, spectrograph, and long-wave infrared imager, the telescope tracks man-made objects in deep space and performs space object identification data collection.