ollimating a telescope means aligning the entire
optical system so that all the mirrors and lenses share the same optical axis
of symmetry. It is not enough to have all their centers lined up as they
must be; each element must also be oriented so that it is mounted perpendicular
to the common optical axis. Collimating then, is the art of positioning each
optical element correctly in 3 planes, (up and down, forwards and back, side
to side) and then orienting each element correctly in its position.
Newtonian Telescopes are unique in that they have
two different axis of symmetry that must be joined to make a single common axis of
symmetry that makes a right angle turn. The position where these two axis meet
is not only critical but also fragile. This is why Newtonian Telescopes need
to be collimated more frequently than the other types of telescope.
