A certain telescope has an objective mirror with an aperture diameter of 153 mm and a focal length of 1610 mm. It captures the image of a nebula on photographic film at its prime focus by an exposure time of 1.34 minutes. To produce the same light energy per unit area on the film, what is the needed exposure time to photograph the same nebula by a smaller telescope, which has an objective lens with an aperture diameter of 51.5 mm and a focal length of 870 mm.