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Windage Compensation
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<blockquote data-quote="blairh" data-source="post: 1301269" data-attributes="member: 54219"><p>I shot IHMSA for years and Ft.Stockton Texas hosted the International Championship on several occasions. Located in west Texas (high desert), not only did the wind blow hard, but the temp typically reached 100+ everyday... making for good mirage. I understand the theories of reading mirage; however, I have another question dealing with its afffect on target acquisition and sight picture... best illustrated by an experiment we conducted one day. At 7:00 AM (70* and no mirage at all) we set a chicken on the 200 yard rail and at the firing line we securely clamped a scope on a steel pole with cross hair centered on the chicken. As the day heated up to 104* in mid afternoon, there was unusually very little wind so the heavy mirage was boiling almost straight up. Looking through the scope under these conditions, the chicken "appeared" to be some 18" (9 MOA) ABOVE the cross hair. The mirage and light refraction was causing the naked eye looking through iron sights to actually "see" the target where it wasn't. If you aimed at what you saw, it was a sure miss high... we had to compensate for where the mirage was bending the light for what we saw. It was an eye opener to say the least! In similar conditions with a 15+ MPH full value wind with heavy mirage, we had to dial the wind and then add a "hold for the mirage"; which under these conditions was holding on the ram's butt to hit him in the shoulder (about 24" or 12 MOA). In all the wind compensation articles talking about reading mirage, I never see this addressed... and it seems to be a real factor. Our vision sees images based on the delivery of light to our eyes and the refraction caused by mirage can "move" the image from where it actually is.</p></blockquote><p></p>
[QUOTE="blairh, post: 1301269, member: 54219"] I shot IHMSA for years and Ft.Stockton Texas hosted the International Championship on several occasions. Located in west Texas (high desert), not only did the wind blow hard, but the temp typically reached 100+ everyday... making for good mirage. I understand the theories of reading mirage; however, I have another question dealing with its afffect on target acquisition and sight picture... best illustrated by an experiment we conducted one day. At 7:00 AM (70* and no mirage at all) we set a chicken on the 200 yard rail and at the firing line we securely clamped a scope on a steel pole with cross hair centered on the chicken. As the day heated up to 104* in mid afternoon, there was unusually very little wind so the heavy mirage was boiling almost straight up. Looking through the scope under these conditions, the chicken "appeared" to be some 18" (9 MOA) ABOVE the cross hair. The mirage and light refraction was causing the naked eye looking through iron sights to actually "see" the target where it wasn't. If you aimed at what you saw, it was a sure miss high... we had to compensate for where the mirage was bending the light for what we saw. It was an eye opener to say the least! In similar conditions with a 15+ MPH full value wind with heavy mirage, we had to dial the wind and then add a "hold for the mirage"; which under these conditions was holding on the ram's butt to hit him in the shoulder (about 24" or 12 MOA). In all the wind compensation articles talking about reading mirage, I never see this addressed... and it seems to be a real factor. Our vision sees images based on the delivery of light to our eyes and the refraction caused by mirage can "move" the image from where it actually is. [/QUOTE]
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