Ewald sphere; x-ray diffraction principle

Clear["Global`*"]

f1[θ_]:=Graphics[{Line[{{-1,0},{1,0}}],Line[{{0,-1},{0,1}}],Red, Thick,Arrow[{{-1,0},{0,0}}],Arrow[{{0,0},{Cos[2 θ],Sin[2θ] }}],Black,Thin,Circle[{0,0},1],Blue, Thickness[0.02], Line[{{-0.3 Cos[θ], -0.3 Sin[θ]},{0.3 Cos[θ], 0.3 Sin[θ]}}],Black, Thickness[0.02], Black,Thin, Table[Line[{{1+a Cos[θ+90°], a Sin[θ+90°]},{1+a Cos[θ+90°] + 2 Cos[θ],a Sin[θ+90°]+2 Sin[θ]} }],{a, 0, 2,0.4}],Table[Line[{{1 +a Cos[θ],a Sin[θ]},{1 + a Cos[θ]+2 Cos[θ + 90°],a Sin[θ]+2 Sin[θ + 90°] }}],{a, 0, 2,0.4}],Line[{{1,0},{1 + 2 Cos[θ + 90°],2 Sin[θ + 90°]} }], Red, PointSize[0.02],Table[Point[{{1 + a Cos[θ]+ b  Cos[θ+90°],a Sin[θ]+b Sin[θ+90°]}}],{a,0,2,0.4},{b,0, 2, 0.4}]}]

Animate[f1[θ],{θ, 0,85°}]