Optics · Explainer
Scope adjustments explained: windage, elevation, parallax and diopter
Researched by James · Updated September 26, 2026 · Editorial policy
On this page
- What does the elevation turret do?
- What does the windage turret do?
- What is parallax and why does it matter on an airgun scope?
- What is the diopter for?
- What order should you adjust these in?
- How do you make elevation corrections on a PCP scope for distance?
- MOA vs MRAD clicks: does it matter which your scope uses?
- Do you need illuminated reticle or side focus, or are they optional?
- FAQ
- Sources
Adjustment mechanics and click values below are drawn from optics manufacturer pages and independent optics guides, cited at the bottom of this page. Full methodology & editorial policy →
New scope owners usually know windage and elevation exist, but parallax and diopter get ignored until groups won't tighten up. Here's what every knob actually does, in the order you should touch them.
What does the elevation turret do?
The elevation turret tilts the scope's internal erector tube up or down, which moves your point of impact to compensate for bullet or pellet drop. Almost every hunting scope clicks in 1/4 MOA, which is close enough to a quarter-inch at 100 yards to use interchangeably in the field; some scopes, especially higher-end or tactical-style optics, use MRAD clicks instead, at roughly 0.36 inch per click at 100 yards. Check your turret caps or the manual before you assume which system you have.
What does the windage turret do?
Windage does the same job on the horizontal axis, moving point of impact left or right. You use it to correct for wind drift at distance, or during initial zeroing to correct for a scope that isn't perfectly centered relative to the bore. Windage and elevation get set together during zeroing; see how to zero an air rifle scope for the full process.
What is parallax and why does it matter on an airgun scope?
Parallax happens when the target image and the reticle don't sit on exactly the same optical plane inside the scope. When that's true, moving your eye off the scope's optical center makes the reticle appear to shift against the target, even though neither the rifle nor the target moved. It's worse at high magnification, on small targets, and at the "wrong" distance for the current parallax setting.
Airgunners feel this more than most centerfire shooters because we shoot at short, constantly changing distances: 15 yards for a backyard squirrel, 45 for a rabbit across a field. A scope with parallax fixed at 100 yards, common on general-purpose hunting scopes built for firearms, will show real aiming error inside 50 yards. That's why airgun-specific scopes like the Hawke Airmax line and Leapers/UTG's Bug Buster series build in an adjustable objective (AO) or side-focus parallax control, often down to 3-10 yards, instead of a fixed 100-yard setting. For more on picking a scope with the right parallax range, see best air rifle scopes.
| Control | What it changes | When to set it | Typical range |
|---|---|---|---|
| Diopter (eyepiece) | Reticle sharpness for your eye | Once, before anything else | ±2 to ±4 diopters |
| Parallax (AO / side focus) | Removes aiming error at a given distance | Before zeroing, and whenever distance changes significantly | 10 yd-infinity (airgun scopes) or fixed 100 yd (many firearm scopes) |
| Windage | Point of impact, left/right | During zeroing; for wind at distance | Dozens of MOA/mils of total travel |
| Elevation | Point of impact, up/down | During zeroing; for distance corrections or holdover dialing | Dozens of MOA/mils of total travel |
What is the diopter for?
The diopter, or eyepiece focus ring at the very back of the scope, focuses the reticle for your individual eyesight, completely separate from the target image. Set it by pointing the scope at a plain, evenly lit surface, like open sky, with no target in the frame, and turning the ring until the reticle lines themselves look crisp. Do this before anything else, because a blurry reticle makes every other adjustment harder to judge accurately.
What order should you adjust these in?
- Diopter — set once for your eye, rarely touched again unless your vision changes
- Parallax — set for your shooting distance before you fire a group
- Windage and elevation — dial in during zeroing, then adjust for distance or wind as needed
Doing this out of order is the most common reason a "zeroed" scope seems to shoot inconsistently: a group shot with the wrong parallax setting isn't a true read on where windage and elevation actually need to go.
How do you make elevation corrections on a PCP scope for distance?
Two ways: dial the turret to a known click value for that specific distance, or hold over using reticle marks without touching the turret at all. Turret dialing is more precise when you know the exact range, which is why it's standard for known-distance shooting; holdover is faster for a hunter who's ranging targets on the move and doesn't have time to count clicks. Building either method into a usable chart takes real chronograph data from your load; see air rifle holdover using mil-dots and MOA for the full process, and the FPE chart for the velocity numbers that feed it.
MOA vs MRAD clicks: does it matter which your scope uses?
It matters for the math, not for basic function. 1 MOA is about 1.047 inches at 100 yards; 1 MRAD (often just called a "mil") is about 3.6 inches at 100 yards. A scope with an MOA reticle should have MOA turrets, and an MRAD reticle should have MRAD turrets — mixing the two forces you to convert units in your head under time pressure, which is where holdover mistakes happen. The full comparison, including which setup suits hunting versus long-range shooting, is in MOA vs MIL: which should you use?
Do you need illuminated reticle or side focus, or are they optional?
Neither is required for good accuracy. Illumination helps in low light or against a dark backstop where a black reticle disappears; side focus (a parallax dial on the turret housing) is just more convenient to reach mid-shot than a front AO ring, especially once you're used to ranging and re-focusing quickly in the field. Both add cost, so weigh them against a plainer scope with better glass at the same price; our best air rifle scopes guide breaks down where that money is best spent.
FAQ
What does the elevation turret do?
The elevation turret moves point of impact up or down by tilting the internal erector assembly, and it's what you dial to compensate for bullet or pellet drop at distance. Most air rifle and rifle scopes move in 1/4 MOA per click, roughly a quarter-inch at 100 yards, though some scopes use MRAD clicks of about 0.36 inch at 100 yards instead.
What does the windage turret do?
The windage turret moves point of impact left or right, correcting for wind drift or for a scope that isn't perfectly centered over the bore. It works the same way as elevation, just on the horizontal axis, and both turrets are zeroed together during initial setup.
What is parallax and why does it matter on an airgun scope?
Parallax is what happens when the target image and the reticle sit on slightly different optical planes, so the reticle appears to shift against the target if your eye moves off-center, even though the rifle hasn't moved. It matters more on airguns than on most centerfire rifles because airgunners shoot at much shorter, more varied distances, and a parallax setting for 100 yards will show real aiming error at 25 yards.
What is the diopter for?
The diopter, or eyepiece focus ring, focuses the reticle itself for your eye, independent of the target image. Set it first, before parallax or zeroing, by looking at a plain surface like open sky and turning the ring until the reticle lines look crisp and black, not the target.
What order should you adjust these controls in?
Diopter first, parallax second, then windage and elevation last. Setting the reticle focus and parallax before you zero means the group you shoot to set windage and elevation is actually representative of your aim, instead of blurred or shifting from parallax error.
How do you make elevation corrections on a PCP scope for distance?
Either dial the elevation turret to a known click value for that distance, using a chart built from your chronographed velocity, or hold over using reticle marks without touching the turret. Turret dialing is more precise for a fixed known distance; holdover is faster for a hunter moving between unpredictable ranges in the field.
Does it matter if a scope uses MOA or MRAD clicks?
Yes, for the math, though not for basic function. 1 MOA is about 1.047 inches at 100 yards, while 1 MRAD (often labeled mil) is about 3.6 inches at 100 yards, so a scope with an MOA reticle and MRAD turrets, or vice versa, forces you to convert between two systems under time pressure. Match reticle and turret units when you buy; see our full breakdown for the complete math.
Do you need side focus, or is a front AO ring good enough?
Either works the same optically; side focus (a dial on the turret housing) is just easier to reach and adjust without breaking your cheek weld, which matters more as you get faster at ranging targets in the field. A front adjustable-objective (AO) ring works fine for a static hunting setup where you're not constantly changing distance.
Can bad parallax adjustment make a correctly zeroed scope seem inaccurate?
Yes, and it's one of the most common misdiagnosed accuracy problems. If parallax is set for the wrong distance, small changes in your cheek position or eye alignment will shift the apparent point of aim shot to shot, which looks exactly like an inconsistent rifle or a bad scope even though the mechanical zero is correct.