All you F-Class HM, Light shift vs POI, Tell me what you know.

[jelenko]

Like a lot of things in shooting, I attribute this to older truths that have lost their context and are no longer valid. With iron sights - a front post and rear aperture - light intensity matters - it's not just mirage. The perception of the size of the bullseye changes a little, and since most shooters seem to hold a sight picture where the bullseye "rests" on top of the sight post, if it appears smaller or larger, that will change your vertical impact point. Throw in that small amounts of mirage are very hard to see without a scope, and you get the idea that light is all that matters if you're shooting irons. In reality, it's a little of both.

With a scope, you don't have that sight picture, and all you see is mirage. With high power F Class scopes, you can see it very well and with a little practice, you know how much the image is lying to you.

That's my experience at least (and a little speculation).

Right. If there is a small dot on the target face and you aim at it with a dot reticle, the POI is not going to change regardless of the amount of ambient light. [Except, maybe for the light flash from a nuclear explosion].

 

[FrankG]

That's really interesting, but I can't help but think that the scope is moving as the day progresses. I've never experienced anywhere near that much movement, even in heavy mirage. The fact that it's a slow and constant movement makes me think it's more related to temperature changes and thermal expansion, and not an optical effect. It doesn't take much of a temperature change to move metal enough to shift the crosshairs. Heating the tripod could conceivably do that - the relatively long legs will expand a fair amount even with small temperature changes.

In that video the spotting scope was mounted to the wooden tower/platform for the match directors and the scope was covered so sunlight wouldn't directly effect it and that wind couldn't bounce it around as well. They did repeat the test with tripods and other mounting methods and the results where all similar.

I think you have to factor in the terrain. Lodi is mostly sand vs just shooting over grass/dirt.

Ever shoot over a small pond? Talk about the moisture/sun reflecting off the water distorting your view thru the scope.

 

[Killick]

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