Expert makes a rookie mistake mounting an optic resulting in sighting and eye strain issues.

Basically because this is a Bullpup design airgun the optic height needs to be different than a standard rifle. The optic fit beautifully on the airgun with the slightly shorter one piece mount but was not perfectly aligned with the sweet spot of my line of sight, causing eye strain. I installed a slightly higher one piece mount and all the eye strain went away. The one piece mount I was using was the same height as I had been using on my standard rifles, and was a "take-off" mount from another project. I was only focused on the optic clearing the rail and fitting the airgun. I did not stop to consider the bullpup design placing my head and eye at a different height. If was so close though that I did start to realize the issue until I got eye strain each time I shot the airgun. I figured I had an optic with a defective lens or something like that and not the slight focal line of sight sweet spot misalignment.