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.
NEOSTEL
The fly eye aspect of the telescope refers to the use of compound optics, as opposed to the single set of optics used in a conventional telescope. Historically, telescopes have been designed around a single human observer looking through an eye piece. As technology has developed astrographs have been used where either a photographic plate or CCD records the image, which a human observer can then view. With the human eye no longer directly observing the image there is no longer a restriction on a single viewing point. Further, as asteroid detection technology has developed, software has become fully automated and no longer requires a human observer to view the majority of images at all. Light enters the telescope through the aperture and is reflected off the primary mirror onto a beam splitter, which is a hexadecagonal pyramid in shape. The split beam then passes into 16 separate aspheric lenses and on to 16 corresponding CCD image sensors. NEOSTEL uses the 16 CCD cameras to view 45 square degrees of light entering the telescope aperture. The resolution is 1.5 arc seconds per pixel across the whole field of view.