A Cassegrain telescope is a reflecting telescope that uses two mirrors, the secondary mirror focusing the image through a hole in the primary mirror (simi1ar to that shown in Fig. 34.55b). You wish to focus the image of a distant galaxy onto the detector shown in the figure. If the primary mirror has a focal length of 2.5 m, the secondary mirror has a focal length of - 1.5 m and the distance from the vertex of the primary mirror to the detector is 15 cm. What should be the distance between the vertices of the two mirrors?