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C11 Mechanical Alignment & Collimation

Possible Causes of Astigmatism.


You shouldn't rely on lasers only for collimation. This illustration shows that it is possible to collimate a scope with a laser and compensate for axial mis-alignment. This will show on a star test as oval airy patterns rotating 90 degrees in and out of focus. Mis-alignment is the main cause of astigmatism in SCTs. Astigmatism can be caused by corrector decentering, primary tilt or decentering and secondary decentering.

Ultimately the star test will tell you if everything is aligned. The field tilt in a CCD picture will also give you any additional information you may need to recenter or realign components.

*note: raytracing for illustration purposes only and may not be accurate. Offset was grossly exagerated to make a point.

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Possible Causes of Astigmatism.