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Old November 26, 2012, 10:45 AM   #29
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
Using a spotting scope to read (see) the mirage (heat waves); lesson 1:

Get a 20X to 25X spotting scope, mount it on a tripod so it's very steady. (NOTE; you can also use a rifle scope of at least 15X that has an adjustable objective so you can focus it at some distant range.)

Go outside on a warm day when the wind's blowing a little bit (no hurricanes at all) to someplace where you can see at least half a mile over reasonably flat ground.

Point the scope at something about half a mile away, then focus it so the image is as sharp as you can get it as you see it.

Note the direction the wind is blowing; left to right or the reverse thereof.

Look through your spotting scope at the thing you focused on then change focus to something closer; move the focus adjustment very slowly.

As you change focus to something closer you should see the wrinkling heat waves (mirage) become clearer and easier to see as they look like running water moving across the scope's field of view. It's the wrinkle close to and just above what your looking at that counts the most.

Move focus as close to where your are as possible so you can see how the mirage appearances changes with focus.

Sit down, take a break then do this over again.

What happens is as the light rays from the far away things go through the air to your eyes, their direction gets changed by the air temperature in it and how its moved around by the cross wind. Find a focus point where you can see the mirage clearly then watch it speed up as the wind speed increases or slow down as the wind drops.

Watching the mirage (reading the wind in competitive shooting language) will let you know whether to move your sights into the wind if it speeds up or away from it if it slows down. Doing this keeps your shots falling at the same place.

How much to move your sights for a given visible wind change? That's lesson two.

Last edited by Bart B.; November 26, 2012 at 10:58 AM.
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