1.
Collimating a Newtonian Scientifically : Incorporating the Cave and Laser Telescope Collimators
by Clark-Fras, Peter R.
ISBN: 9781665584012
2.
Collimating a Newtonian Scientifically : Incorporating the Cave and Laser Telescope Collimators
by R. CLARK - FRAS, Peter
ISBN: 9781665580830