Astronomers are attempting to observer a star being occulted by the Moon at a latitude on the lunar disk of 85S. Assume that Moon moves in a circular orbit, of 384,400 km, at a speed of 1 kms-1.

a) They determine, from high-speed photometry, that the occulted star took 0.229 sec to fade. What is the diameter of the star in milli-arc seconds (mas)?

b) A subsequent very careful study of the light curve reveals a second small fade, presumably from a secondary star of the above, some 0.8 sec later. What is the minimum angular separation between that and the bigger star from (a)?

c) Why is it described as a "minimum separation" and how would you find the true angular separation?