I did some optical simulation for a Newtonian(reflector) telescope using my office's Zemax raytracing optical CAD program. The purpose is to show beginners why collimation is important in a optical systems. The simulated optical system is a 8inch F/6 Newtonian. The primary parabolic mirror is purple in colour, the diagonal is cyan in colour. The blue lines are the parallel light rays (star light is generally parallel) that enter the reflector. The parallel light is reflected by the parabolic mirror and in turn reflected by the 45 degree diagonal into the eyepiece. The focuser is the almost transparent cylindrical blog. A flat square shape 'sensor' is placed at the focal plane. When properly collimated, the light rays will focus onto the CENTRE of the focal plane.
A) Properly collimated
B) Parabolic mirror misaligned by 0.1 degree; diagonal aligned properly. Notice the slight shift from t centre of the 'sensor' compared to (A)
C) Parabolic mirror misaligned by 0.4 degree; diagonal aligned properly. Considerably out of the centre of the 'sensor'
D) Diagonal misaligned by 0.5 degree. Parabolic mirror aligned properly.
From these simulations, it can be seen that a slight misalignment of the parabolic mirror will affect the focus position considerably. The diagonal misalignment is not so significant compared to the parabolic mirror.
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