Astronauts observing from a space station need a telescope with a resolving power of 0.9 arc seconds at a wavelength of 540 nm and a magnifying power of 260. Design a telescope to meet their needs. (State the necessary primary diameter of the telescope, in m, and the ratio of the focal lengths below. Also, what will its light-gathering power be, compared with a dark adapted human eye? (Assume that the pupil of your eye can open to a diameter of about 0.8 cm in dark conditions.)

Astronauts observing from a space station need a telescope with a resolving power of 0.9 arc seconds at a wavelength of 540 nm and a magnifying power of 260. Design a telescope to meet their needs. (State the necessary primary diameter of the telescope, in m, and the ratio of the focal lengths below. Also, what will its light-gathering power be, compared with a dark adapted human eye? (Assume that the pupil of your eye can open to a diameter of about 0.8 cm in dark conditions.)