Back reflections

Examples of back reflections from aligning optics.

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Objective 60cm from back

Moving the viewing screen further away from the optic can be helpful (if there's space). It exaggerates imperfections in alignment and optical components. Here's the same setup as the 15cm example, but with the screen at 60cm. It is clearly well aligned:

objective_60cm_from_back_aligned.jpg
Back reflections from a Nikon 40x0.95 air objective (MRD00405) with a viewing screen ~60cm from the back (aligned).

Here's the same setup with some horizontal tilt misalignment. The lack of radial symmetry is pronounced. This is not well aligned:

objective_60cm_from_back_misaligned.jpg
Back reflections from a Nikon 40x0.95 air objective (MRD00405) with a viewing screen ~60cm from the back (misaligned).