1. The problem statement, all variables and given/known data A reflecting telescope has a radius of curvature of 3.0m for its objective mirror and a radius of curvature of -1.50m for its eyepiece mirror. If the distance between the two mirrors is 0.90m, how far in front of the eyepiece should you place the photographic film to record the image of a star? 2. Relevant equations I could only find out the focal length of both objective mirror and eyepiece mirror. f=radius of curvature / 2 .....(1) 1/f = 1/di + 1/do .....(2) 3. The attempt at a solution For now, I got fo=1.5 and fe=-0.75 as the object are from infinity , by using equation 2, di=fo=1.5 Since the distance between the two mirrors is 0.90m , and 1.5-0.9=0.6 0.6 is the object distance of the eyepiece. 1/-0.75 = 1/di + 1/0.6 di is -0.3333 I haven't taught reflecting telescope in my class. I just find a similar solution in yahoo answer. But I feel the ans is totally wrong. Can anyone help me?