Firearm Scopes And Optics

Scopes, Where do I Start?

O.K. you have your nice rifle. You look around for a proper scope, but don't really know what to get because you are so overwhelmed. There are hundreds of different scopes out there. You see numbers, letters, and different shapes and sizes. The intention of this article is to hopefully make it just a bit easier to gather some information on scopes to make a better purchase.

Where do you start? Customers sometimes ask, "What scope do you think is the best?" I always tell them, "Well, it depends on what you want to do." Then I go into my informative speech and relay common facts of scopes. Let's start. First and foremost rule of thumb, buy the highest quality you can afford.

Types

Basically, there are a couple of types of scopes, magnified and non-magnified. There are of course many sizes, shapes, and colors but that is usually for design purposes and personal preference.

Magnification

These are indicated in the numbers of the specifications of scopes usually printed on the box or right on the scope itself. There are variable magnification scopes, set magnification scopes, and non-magnification scopes. For example, a common 3-9x40 scope is letting you know that the range of magnification is adjustable from "3" times magnification to "9" times magnification. The "40" is usually expressed in millimeters and is the diameter of the objective lens (rear lens opposite the eyepiece (ocular).) Another example would be 1x29. This scope would indicate that the magnification is 1 time and the objective lens diameter is 29 millimeters. There are several different ranges in these numbers. From magnification of 1 to 40 times plus, with objective lens diameters up to an incredible 75mm. Generally, for most individual needs a 3-9x magnification is just fine. So what do these numbers mean for performance. Well, here are a couple of things to start.

No magnification to small magnification benefits:
-More light transmission.
-Larger field of view. (How much field (surroundings) you can see through the scope.)
-Usually means smaller scope, so more lightweight and less bulky.

Light transmission

Good quality scopes mean good light transmission. Light transmission is how much light is transferring through the medium (lenses) to the eye. 100% is not obtainable (being that light must travel through a medium different than air) and 95% plus is excellent transmission with most scopes around 90% or so. This is usually nothing more than quality of lenses and lens coatings. Lenses are coated with different quality of coatings which may add to better light transmission and durability. They are also different processes of coatings indicated here:

-Coated lenses- One side of each lens is coated.
-Fully coated lenses- Both sides of each lens is coated.
-Multi-coated lenses- Multiple layers on one side of each lens is coated.
-Fully multi-coated lenses- Multiple layers on both sides of each lens is coated.

Field of view (F.O.V.)

Fields of view is nothing more than how much of the scene (surroundings) you can observe through your scope. The Field of view change with magnification becoming smaller as the magnification increases. In other words, as you increase the magnification of the scope, the less you can observe of your surroundings. An F.O.V. is usually expressed in either feet or in degrees. Feet are going to indicate the length of the background (surroundings) that you can see. For example, an F.O.V. of 24ft at 100yards is that for a 100 yard scene you can see 24 feet across of landscape or surroundings. For degree computation, 1 degree is equal to 1.75. (For more information on this computation, visit www.macarms.com and observe the video on F.O.V. in the information section.)

Eye relief

Eye relief is a simple measurement usually expressed in inches. This is the distance from your eye to the eye piece of the scope. Most scopes are around 3 inches and can go up to around 5 inches. 4 is considered great. On eye relief, what you sometimes need to be concerned with is for higher recoil rifles you may want a higher eye relief to prevent a nice black and blue shiner. This can always be comical in that you will have to make up some story to your friends about warding off a bunch of hoodlums some night or you received laser eye surgery and they messed up big time.

MOA

Minute of angle or arc is a measurement in degrees. Basically, there are 360 degrees in a circle in which you can fire in. The factor is 1 minute of arc is equal to 1/60 degrees. What does it mean for usable measurements? It translates to your windage and elevation adjustments on your scope. Since the actual computation for MOA at 100yard equals 1.047 inches, you can adjust your scope so many "clicks" to zero in on your target. Scopes can be calibrated differently, but many use 1/8 inc or inch clicks to adjust for windage and elevation. Again, it basically means that for a inch click scope, if you click one time it will adjust your rifle to shoot inch in that direction at 100yards.

Exit pupil

Scopes are optical devices. They use light to transmit an image through lenses just like our own eyes. Scopes follow this same principle. Think of it as the scopes "eye" as it allows so much light into "its" eye, just like our own pupils. The larger the pupil the more light is let in. The formula for exit pupil is: objective lens/magnification = exit pupil. Units are expressed in mm. A neat way to get a look at a scopes exit pupil is to hold the scope at arms length and look through it. Try it at low magnification and then again at higher magnification and observe the difference. More magnification equates to smaller pupil size. Exit pupil affects a couple of things. Light transmission is less when magnification is greater. Also, the larger the exit pupil the less critical you head placement needs to be when looking through the scope.

Parallax

Ah, parallax. Well, this is always a little difficult for most people to grasp. Parallax is sort of like Einstein's theory of relativity where motion depends on the observer. Well, the image you see depends on your position and point of view. Let's try a small example. Take a look at an object where ever you are in the distance such as a light pole, light switch, person, or something. Now hold your thumb out at arms length to cover up the object. Then, without moving your thumb, move your head left or right. Notice that you even though the objects are in the same position your point of view is now different for both objects. This is the basis for parallax. Objects can appear to be in a certain position when in fact they are not. This parallax can affect image position more so for objects that are closer to you position. If a scope has parallax adjustments, they are supposed to alleviate some or most of this. Another example is to look through your scope and line up the crosshairs on specific point of an object. Then, without moving the scope, move your head around slightly. Notice how the crosshairs will move off the specific target you just had the crosshairs on.

Repeatability

Good scopes should be able to adjust precisely, over and over. Meaning that you should be able to adjust for windage and elevation and then go back to "center" with the same adjustment in reverse. In other words, if your scope is zeroed in and you adjust 2 clicks left, your bullet should reflect that. Then you should be able to adjust 2 clicks right and be right back perfectly on target. This would suggest good quality.
In conclusion, I hope to have shed some light on some information about scopes/optics. Look for good quality scopes for you rifle because if you cannot line up your sight on a target properly every time and hit it, then what good is shooting a bullet to just fly through the air?

Source: http://www.articlesnatch.com/Article/Firearm-Scopes-And-Optics/4160668

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