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What Is an AO Scope [Adjustable Objective Optics]?

Dakota Potts | Updated February 25, 2024 | Why You Should Trust Us | How We Earn Money
What is an AO scope cover photo showing a hand adjusting the side focus of a scope

If you’re a gun enthusiast, you’ve probably come across an AO or an adjustable objective scope. But what is an AO scope, exactly, and how does it work? If not, you’ve come to the right place.

Below, we explain how this scope works, its pros and cons, and how to use it. Let’s get started.

For more reading see are article on some of the good long range sniper scopes available.

What Is an AO Scope?

An AO scope is a type of scope you can tweak or adjust the reticle’s focus so that there is no parallax at the distance you’re shooting. This feature is essential, especially in long-range shooting, where a minor adjustment in focus makes a huge difference in whether you’ll hit the target.

The defining feature of this scope is the adjustable objective lens that gives shooters a precise and clear image of the target despite the lighting conditions and distance. The adjustment is usually a knob on the left side or a dial around the objective end of the scope.

You can get AO scopes in various magnifications. This includes low-power scopes ideal for close-quarter combat to high-power scopes used in tactical applications or long-range shooting.

The magnification range will be indicated by two numbers separated by a hyphen, like 6-24x or 3-9x. The first number is the lowest magnification setting, and the second is the highest magnification setting.

Check out this in-depth video that explains how an adjustable objective scope works:

Pros and Cons of an Adjustable Objective Scope


  • Allows for accurate distance estimation: AO scopes can allow you to accurately estimate the distance to your target. By fine-tuning the focus to match your target, you can get a clearer view, making it easier to estimate the distance.
  • Improved image quality: Superior AO scopes produce high-quality images even in low-light conditions.
  • Eliminates parallax error: Parallax error occurs when the reticle and the target aren’t in the same plane, so when you move your eye position, the reticle position shifts, causing shots to be off-target. With an AO lens, you can adjust the focus, eliminating the error and allowing the reticle and target to remain in the same plane.
  • Versatile: An AO scope can be used in different applications, such as target shooting, hunting, and tactical shooting.


  • Costly: With all the benefits we’ve mentioned of AO scopes, they come with a notable price tag.
  • Learning curve: Learning to use an AO scope takes time, especially if you have been using a fixed scope. You have to learn how to focus correctly, estimate distances, and factor in other things that can affect accuracy.

How to Use Adjustable Objective Scopes

AO scope with fingers turning scope knob on the left and a reticle on the right

AOs are popular among target shooters, hunters, and tactical shooters because of their enhanced image clarity. Here’s how to use this scope. (Reference: AO Scope)

  1. Determine your distance: Estimating the distance to your target lets you adjust the focus on the lens, ensuring both the target and the reticles are in the same plane.
  2. Adjust the lens: After determining the distance, adjust the focus knob until the target is clear.
  3. Aim and shoot: Once the AO is properly adjusted, aim your rifle and fire. If you’re changing the shooting distance, you must adjust the focus again.
  4. Practice and more practice: Using an AO scope requires a lot of practice to familiarize yourself thoroughly with this mechanism.

Up next see: what sniper rifles marines use today.

Frequently Asked Questions

What does AO in scopes mean?

AO in scopes stands for adjustable objective, meaning you can adjust the scope to fix parallax errors.

Are AO scopes good?

AO scopes are good because they allow the shooter to easily adjust the reticle’s focus without moving their head or changing their shooting position. This is helpful, especially in scenarios like precision shooting or hunting.

What is adjustable AO scope?

An adjustable objective scope features an adjustable lens that lets you modify or fine-tune the scope’s focus, compensating for parallax error.

What is the difference between adjustable objective scope and fixed?

The main difference between adjustable objective scope and fixed scope is that with the former, you can adjust the focus to match the distance to the target, eliminating parallax error. With a fixed scope, there isn’t an adjustable objective lens, meaning the scope is set at a specific distance.


  1. Steven L, Rifle Scope Glossary of Term. Retrieved from https://www.opticsplanet.com/howto/how-to-understand-rifle-scope-terms.html

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