Mirage.
If I understand the statement in your question, the person asserts 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 have played with the study of Mirage for the past 3 years and 2 days a week. The Mirage is an interesting phenomenon. Mr. Mann is somewhat right about the 200-meter distance of 200 yards. However, it would depend upon what you are shooting. Mirage raises hell on a 22 Long Rifle at 200 yards.
What is mirage? Mirage is a series of wavy lines in the Air. The lines may move right, left, upwards or in any degree of angle from the earth surface. When the Sun is shining on the earth, the surface is heated. The heated earth creates wavy lines going straight up as the heated air rises from the surface.
If there is a slight wind, the mirage will go from straight up to the direction the wind is blowing. It may appear to be horizontal in a heavy wind or at any angle covering the 180-degree flat surface of the ground. It can reverse direction in a moment without considerable notice.
A fast moving bullet will still be subject to the disturbance that we see in the Mirage. Actually, the reason that the Mirage is moving other than straight up is the wind. The wind will affect the path of a bullet to a degree, depending upon bullet weight and velocity. The mirage does not actually affect the Point of Impact. The cause, that makes the mirage move, does in fact cause a different POI of the bullet.
When you are reading the Mirage for left to right movement, you are in fact determining the severity of the wind affect on the bullet travel.
Mirage and elevation: This is a tricky subject and a lot of people may not agree with me. As I have declared, I have spent several years spotting for numerous caliber TC Contenders, Encores and rifles up to 45-100 BPCR. I have made a study of the effects of Mirage.
Example: Lets say that the mirage appears to be rising at a 45-degree angle to the right at 500-Meters. The mirage is best read with some kind of a background, like the Target Rail, that is black or a dark color. The mirage reading says that the wind is blowing the vertically rising heat waves sideways and makes them appear at a 45-degree angle to the right.
Now, lets really talk about what a mirage is. A mirage is an image created in this case by the heat waves and the wind blowing it.
When I first started noticing what the mirage was telling me, we had been shooting all morning at 500 meter Rams and punching them dead center with 308s and 7mm Mausers. The temperature was cool and comfortable. We took a lunch break and exchanged lies for about an hour. We resumed shooting and the perfect shooting rifles are now hitting 2 feet high and a foot to the right of the Rams head. Out of absolute frustration, I held the POA at the foot of the rear leg. The ram was facing right on the railroad rail stand. I hit the Ram high and slightly right of dead center. My buddy did the same thing and had hits too.
What happened? The sights had not changed during lunch, but the heat of the day changed and the wind from the left came up.
My theory on this situation is that the Ram didnt duck or move, but the picture (Mirage of the Ram) moved with the rising heat waves that are being blown right at a 45-degree angle. If you aim at the Mirage, you will, in-fact shoot where we see the Mirage Picture. When the wind blows strong enough from the left, the mirage lines will spread severely and appear to be moving sideways. In this circumstance, you are fighting the Mirage and the Wind. I have held as much 8-feet left with a slow moving 30-caliber bullet (2000fps). Did a 10 mph wind move the bullet 8 feet or some portion there of? Or is it a combination of the Picture Mirage moving and the wind also affecting the bullet drift? I personally, think it is both. If I know my firearm or another persons arm, I can look at the mirage at 500 meters and call your POA for a hit, depending on the reading.
Two days during the week and 2 additional Saturdays a month, you will find me at our shooting club. I shoot and my buddies continue to hone their skills at reading the mirage and wind. They shoot and I spot for them.
We have done the 1,000-yard Black Powder Cartridge three-day match and I spotted for two shooters. Using my stated theories above, they came in 2nd and 3rd place in the State Championships.
I do not proclaim to be an expert in this field, but I have paid attention and have made a sport of spotting and calling shots for myself and other shooters. It is an art form, much to my dismay. I would prefer that it was logical so I could analyze and make a calculation from my findings. Well, that is not happening.
I hope this has been of some help to you.
Harold Clark