I presume you are using the plottools and plots packages.
So a is a "point" that could be displayed in a plot. (Actually the thickness=6 doesn't do anything: if you want something visible you might try
a:= point([1,0,0], color=red, symbol=solidcircle, symbolsize=6);
You can rotate this about some axis by some angle, obtaining another "point", e.g.
You could animate this rotation. Actually animate wants a plot structure, not just a component of a plot structure, so you could try e.g.
c:=animate(rotate, [display(a), Pi, [[0,0,0], [1,2,cos(t)]]], t = 0 .. 2*Pi);
I'm not sure what you're trying to do with op in the next command. Do you mean you want the x, y and z coordinates of the points that are plotted in this animate command? You can do something like this:
cx, cy, cz:= seq(map2(op,i,L), i=1..3);
If you had a curve rather than an animation, it would be somewhat easier: you could use the getdata command.