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Re: Mirage

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30 November 2004, 14:38
trk
Re: Mirage
Quote:

I'm working my way through "The Bullet's Flight From Powder To Target", and it ain't easy. Franklin Mann discusses mirage on pages 177-180; describes his testing, and concludes that "...no mirage could be detected, in slightest degree, to affect telescope lenses or change the position of cross hairs on target up to 200 yards."
I've read the section many times, and think that I understand what he said and what he did.
His conclusions seem to fly in the face of the conventional wisdom concerning mirage. Could all the more recent work that I've read about shooting in mirage be wrong?
joe b.



Joe B. -

I read the experiment quite differently. There was no gun involved. There was no heat source (the barrel) to cause the boiling mirrage we're all familiar with. I see no contradiction with 'conventional wisdom'. I see the experiment being that as limited to 3 directions, measurements taken many times over several days. His conclusions were limited to that setting as he described - with no perceptable influence. That is much different from putting the scope on a rifle and pulling the trigger many times - creating the heat source that causes the mirrage right infront of the objective lense.

That's my two cents worth.
01 December 2004, 06:29
trk
In my book, mirrage is the changing angular deflection of light caused by variation of heat in the media.

I think all he was saying was under the condtions he noted that there wasn't anything measurable.

I think also that the value of his experiment is to teach us to prove (one way or the other) HOW MUCH effect the mirrage from the range where WE'RE shooting has.

Anyone who's flown a light plane knows the difference in heating of the air from a field in grain vs. one that's just been plowed.

Most of us can visualize the mirrage above a long stretch of road ahead of us while driving.

The question is how do we recognize where the mirrage is coming from and how do we overcome it's effects. My old eyes like what Waksupi said about just aiming in the middle of the blur.
01 December 2004, 00:05
joeb33050
I guess that there are at least two things called mirage. The barrel-heat mirage isn't what Dr. Mann is talking about. The ground-air-hot mirage is what he is talking about, and what he says isn't there. Certainly it should have been. I think.
joe b.
01 December 2004, 18:30
waksupi
Chief of Smoke, Pulaski Coehorn Works & Winery

Ken, got any Tshirts with that on it?

Being out of the hot season here for the next six months, I can't do a lot of mirage checks. But I will put it on the "to do" list for next summer, and see what I can learn.