Here are the answers that I can remember for Astrophysics. Bear in mind that not all of them may be correct or in the right order.
1) (i) Closest distance was sqrt 2.57^2 + 1^2 x 1.5x10 11 = 4x10 11
(ii) Show that theta = 3.12x10 6 radians
(iii)Draw a Casegrain telescope (the correct diagram is shown in the June 2011 Mark scheme)
(iv)The crater can be resolved in detail because the angle subtended is larger than the theoretical min. resolving limit
2) (i) Six marker, Don't ask.
(ii) m - M = 5log25/10 = -0.0097x10-3
3)(i) T = 16111K
(ii) The star was actually a white dwarf but I messed up and put main sequence
(ii) H balmer lines because the star's atmosphere was hot enough to have hydrogen in its n = 2 state
4)(i) A black hole is an object whose escape velocity is greater than c
(ii) Schwartzchild Radius, can't remember.
(iii) 4.96x10 18 s
Please feel free to message me so I can add or change things and to show the number of marks available for each question.