The slant distance, T, from the center of the secondary to focal point of the system is given by Eq. (4):
Finally, the relationship between the angles of tilt of the two mirrors is given by Eq. (5):
where A and B are the angles of deflection of the central ray by the primary and secondary mirrors respectively (see Figure 1).
Experience with the design of the light-baffle system for the Yolo reflector has shown that by designing the optical system to bring the focal point well back of the plane of the primary mirror, the "muffle" (that part of the light-baffle system which is located forward of the secondary mirror) can be shortened very appreciably. It is recommended, therefore that T be made about 1.2 times S. When this condition is combined with Eq. (4), the following is obtained:
Although R1 and R2 need not be made equal, in most practical designs they will turn out to be not
greatly different; and there is no good reason why