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What does an objective lense do on a scope?

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What does an objective lense do on a scope?

Old 01-12-2006, 11:11 AM
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Default What does an objective lense do on a scope?

I bought a new simmons scope with an objective lense but it does not explain what it does in the instructions.
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Old 01-12-2006, 11:29 AM
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Default RE: What does an objective lense do on a scope?

Do you mean an adjustable objective lense???
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Old 01-12-2006, 11:36 AM
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Default RE: What does an objective lense do on a scope?

YES
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Old 01-12-2006, 11:46 AM
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Default RE: What does an objective lense do on a scope?

If your sitting in you car in the drivers seat and look at your speedo and its on 55mph and at the same time someone in the passenger seat looks at the speedo itll look like your going 52 or so when your still doing 55, that optical illusion is called a parallax.


Scopes all have parallax's in them. The non adjustable kind are usually set at 100yrds unless its a shotgun scope which is usually set about 50 or 75 yards. Your scope will let you chose where to set it where there is no opticle illusion and your x-hairs will be on exactly what you are looking at. Most people I know set the adjustable objectiveon about 100yards but you can taylor it to you hunting situation. If you take longer/shorter shots most of the time you can set it where you like.Generally scopes of 12x power and higher have the adjustable obective A.O. because you can see more detail further away.

This is a very short explanation and if you search the net a little you can prob get alot more indepth with the answer or someone here with a little more time will add a little more you can always count on that.
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Old 01-12-2006, 12:01 PM
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Default RE: What does an objective lense do on a scope?

The objective lens is the one on the opposite end of the scope from the one you look into. That is, it's the one closest to the "object" you're looking at. The one you look into is called the ocular lens.

An adjustable objective lets you adjust out parallax at the distance you select. Parallax is the apparent movement of the reticle in relation to the target as your head moves around behind the scope. This is because the image of the reticle and the image of the object you're looking at are in two different opticalplanes.For example, if you set your Adj. Obj. for a distance of 150 yards, then look at an object at that same distance, then the reticle (crosshairs) will stay put on the same spot even if your eye doesn't stay exactly in the same place behind the scope. If you look at an object at a different distance, say 300 yards, andwhile doing somove your head from side to side, the reticle will move slightly in relation to the target and not stay on the exact same spot.

Hope that helps explain it.
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Old 01-12-2006, 12:56 PM
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Default RE: What does an objective lense do on a scope?

Objective lens size-
The front objective lens is like a funnel,gathering light,and in theory,the bigger it is the better.This is great if the rest of the scope is a quality piece of equipment,but more and more "cheap" scope manufacturers are using large objective lenses just to sell their products.If the internal lenses of the scope are not quality made,the objective lense size will make no difference.Another advantage to having a large objective is that you will be able to see better early in the morning and later in the evening,due to the increase in light transmission.The downside to big objectives of course is their bulk and weight.It sometimes becomes awkward to carry that heavy barreled rifle with a scope featuring a 50mm objective,take this into consideration when choosing your scope.Most scopes today have a 40mm objective lens and this is fine for most applications.
Adjustable objectives-
Having an adjustable objective lens means that you can focus it,which means a sharper target image and also reduces or eliminates parallax.What is parallax?Parallax is the tendency for scope crosshairs to shift and change point of impact if the shooter moves his head.Not usually a problem with quality scopes of about 10X or less,but can be a problem above 10X unless the scope has an adjustable objective lens.Most scopes that have adjustable objectives use an adjustable ring on the objective lens,some use a knob on the left side of the tube.
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