Parallax question

[tsonda]

Background, I have a 10yo shooting in some low key competitions out to 1000yds. I have set the parallax to my eyes and marked it on the knob for our known distances. If the ocular focus knob is not moved will the scope stay parallax free even if his eye is in a slightly different distance from the scope than mine. I would think that parallax free is parallax free if the ocular focus knob is not moved.

 

[ncr92]

Based on my rudimentary understanding of optics, focus adjustment should not have an effect on parallax error. The objective lens assembly and erector assembly produce real images at the first and second focal planes. The parallax adjustment makes small adjustments to the position of one of these real images to align it with the reticle. The ocular lens assembly produces a magnified virtual image of the real image at the second focal plane. Adjusting the focus just changes the focal length of the ocular lens assembly to bring this virtual image into sharp focus. This adjustment should not cause the reticle or the real image in the relevant focal plane to move and therefor should not have any effect on parallax error.

 

[_Raining]

10 yo's are probably better at using smart phones/computers then adults, they might not have any issues learning the head wiggle or diopter setup.