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Figure 1C. Secondary mirror correctly aligned (tilted).
Figure 1A. The view down the focuser tube of a Newtonian
reflector with eyepiece removed. In this example, the optical
system is badly out of collimation.
Figure 1D. Primary mirror correctly aligned. The telescope’s
optical system is now collimated.
Figure 1B. Secondary mirror centered under focuser tube,
viewed through the Collimating Eyepiece (as are the next
two illustrations).
