Ever been frustrated by “black clouds” when you’re trying to look through a scope? Here are a few thoughts on preventing that…
Source: Barbara Baird for NRA Family
First, remember that your eye is the rear sight. You have to place it in the same place with regard to the rest of the gun every time to avoid a parallax error when using the scope. So…what is parallax?
Parallax is an apparent displacement against a background, or a difference in orientation of an object, when the object is viewed along two different lines of sight. Parallax is measured by the angle or semi-angle of inclination between those two lines. In a riflescope, parallax is an optical illusion. Parallax occurs when the “primary image” of the object is formed either in front of, or behind the reticle (crosshair) of the scope. When you move your eye from its proper alignment with the scope, the resulting parallax moves the image in relation to the crosshair, causing your aim to be off.
Think of it this way. You’re sitting in the passenger seat of the car and you look over at the speedometer. It will read differently to you than to the driver, and that is because you’re not lined up with the steering wheel and gauge in front of it, so you’re not getting the true reading.
Every scope has a quality called “eye relief.” That’s the distance behind the eyepiece lens that your eye should be placed to be able to see through the scope effectively. You have to place the cheek of your shooting eye against the stock; move your head forward and backward along the stock-always with your cheek against the stock-until you get the best view through the scope.
The best view is when sight picture in the eyepiece lens fills the entire lens. As you move your head forward from the best viewpoint, the picture collapses, and when you move your head back from the best viewpoint, the picture starts to get smaller and then goes black. If it’s possible, it’s very important to position the scope itself so you attain correct eye relief using the head position you are most comfortable with. Do that by moving the scope mount or the scope within the mount forward or back. Whether this can be done depends on the mounting system.
If it’s not possible to choose a new scope mounting position, find the right spot to allow full view through the scope, as described. Either way, then practice getting the same “cheek weld” (the position and pressure of your cheek against the stock) every time you shoulder your rifle and you will be one step further in taking a good, clean shot.
Addition from Midsouth Editor Glen Zediker:
One of the reasons I usually test from position (prone) rather than from a benchtop when I’m wringing out a competition-use load has a lot to do with scope positioning. Two things: if there’s already a scope mounted, I don’t want to change its position, and, if there’s not, the difference in my shooting position prone and from a chair could well influence my on-target impact results. Almost always, the scope needs to be scooted farther back firing from sandbags and farther forward for prone or offhand. I offer this as a caution to those who might take a new rifle with a new scope to the range and get it sighted in from a rest, and then get out into the field with it and find out they’re having to pull their head back to see through the scope properly.