This invention provides a reflecting-refracting, i.e. catadioptric, telephoto lens of F/7 and having an angle of field of 5 DEG . The lens system comprises a positive meniscus lens having a convex surface directing toward an object, a main reflecting mirror of concave back surface having a refracting surface and a reflecting surface, an additional mirror of convex back surface placed near to said positive meniscus and having a refracting surface and a reflecting surface, and a concave lens cemented to said reflecting mirror through a positive lens placed therebetween and having a concave surface directing toward the object. The central portion of the main reflecting mirror is not reflecting; it allows the passage of light. The composite focal length of the negative lens, positive lens and the main mirror is negative when the light rays pass therethrough and the assembled length of the system is less than 1/3.5 of the focal length of the whole system.
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