Patent ID: 7920324

Claim:
A method of controlling the positioning of a main telescope having an associated guide scope and an imaging means, comprising: creating an artificial reference star in the field-of-view (FOV) of said guide scope which is locked to the line of sight of the imaging means of said main telescope; selecting a real guide star which is within the FOV of said guide scope, said guide scope having an associated focal plane on which said artificial and real guide stars are focused; and maintaining said line of sight such that the positional displacement between said selected real guide star and said artificial star on said guide scope's focal plane is maintained approximately constant; wherein said creating of said artificial star comprises: generating a point source of light in the vicinity of said imaging means within said main telescope; directing light from said point source outside of said main telescope via its aperture, said light from said point source exiting said aperture being an output beam; and retroreflecting said output beam at the same direction angle of the beam exiting the aperture into said guide scope.