Complete the diagram, with a Newtonian mounting, continuing the two rays to show how they pass through the eyepiece.

When the Earth-Moon distance is 363 300 km, the Moon is observed using the telescope. The mean radius of the Moon is 1737 km. Determine the focal length of the mirror used in this telescope when the diameter of the Moon’s image formed by the main mirror is 1.20 cm.

The final image of the Moon is observed through the eyepiece. The focal length of the eyepiece is 5.0 cm. Calculate the magnification of the telescope.

The Hubble Space reflecting telescope has a Cassegrain mounting. Outline the main optical difference between a Cassegrain mounting and a Newtonian mounting.

plane mirror to the left of principal focus tilted anti-clockwise

two rays which would go through the principal focus

two rays cross between mirror and eyepiece AND passing through the eyepiece

eg:

\(\frac{{2 \times 1737}}{{363300}} = \frac{{0.0120}}{f}\)

f = 1.25 «m»

Allow ECF if factor of 2 omitted answer is 2.5m

M = \(\frac{{1.25}}{{0.05}}\) = 25

parabolic/convex mirror instead of flat mirror

eyepiece/image axis same as mirror