Back reflections

Examples of back reflections from aligning optics.

Objective 20cm from front

Here's an example of finding the optical axis of an objective by going into the front. This is slightly harder since the front element is small (~0.5mm field of view here), but the result is similar to going into the back:

Back reflections from a Nikon 40x0.95 objective (MRD00405) with a viewing screen at ~20cm from the front element (aligned).