Subject: parralax on 1-4x scopes
Posted: October/30/2015 at 16:45
Dawgdad;
I'm concerned that you are taking 24 mm as the parallax error for your specific set of factors, and if so, that isn't correct.
Koshkin gave you the information needed to answer the specific question you asked, but he left it to you to solve for your specific circumstances. Please note that he used a 24 mm objective, 4X, and a 150 yard parallax correction distance for his examples, not 34 mm, 4.5X, and 100 yds.
As Ilya noted, when ones eye is not all of the way to the edge of the exit but is offset a certain amount (he used a 2mm offset from the scope's optical axis), then parallax error is not maximum. Under these realistic circumstances, the P.E. for this offset can be calculated as:
P.E. = Eye Offset x Magnification x (target dist - parallax correction dist)/parallax corr dist.
For the specific set of values you set out: 4.5x, 34mm Objective, 100 yd parallax corr dist, and shooting at 600 yards, P.E. = 2 mm x 4.5 x (600 yd - 100 yd)/100 yd = 45 mm or 1.77 inches.