A short plane mirror or converging secondary mirror is used to reflect the light back down the telescope tube through a hole at the center of the objective mirror.
(A short plane mirror or converging secondary mirror; is used; to reflect the light back down the telescope tube through a hole at the center of the objective mirror) (A short plane mirror or converging secondary mirror; to reflect; the light; back down the telescope tube)
A short plane mirror or converging secondary mirror A short plane mirror or converging secondary mirror
is used to reflect
to reflect the light back down the telescope tube through a hole at the center of the objective mirror
the light back down the telescope tube