When archers talk about first axis, second axis, and third axis, the numbering implies something like X, Y, and Z — three independent spatial axes, each addressing a different dimension. That is not what they describe. First and second axis are the same axis. Both are about the cant of the bow — the roll around the line of sight. The numbering scheme has confused archers for years by making one problem sound like two, and by failing to name a fourth adjustment that actually matters.
Better terms exist. This article uses them.
The names, corrected
The four sight adjustments and what they are actually correcting:
- Bow cant (first axis) — whether the slider rail is set to the intended reference angle
- Tilt (second axis) — whether the bubble housing is calibrated to read level at that reference angle
- Scope yaw (third axis) — whether the scope face is pointing in the correct horizontal direction, as viewed from above
- Scope pitch — whether the scope face is tilted upward or downward from perpendicular (not traditionally numbered)
Bow cant (first axis) and tilt (second axis) are not two axes. They are two parts of one axis — both addressing the roll of the bow. Bow cant sets the physical reference. Tilt calibrates the indicator to that reference. Scope yaw (third axis) and scope pitch are genuinely different adjustments on genuinely different axes. The traditional names get the count wrong and hide the relationships.
Bow cant (first axis)
The slider rail is the vertical track the elevation housing rides on as you move your pin for different distances. Bow cant (first axis) is whether that rail is set to the correct reference angle — typically vertical, or at whatever deliberate cant angle you intend to hold.
When the rail is canted, moving the housing up or down for different distances also moves it laterally. A canted rail introduces a windage offset that changes with distance. The error accumulates across the span of a sight tape. That said, tilt (second axis) is typically the more critical issue for slider sights — the bubble is the reference on every shot, and a miscalibrated bubble affects every arrow. The canted rail shows up differently: as windage that shifts as you change distance, not as windage that is consistently wrong.
Bow cant is adjusted at the sight's riser mount, or further along the sight assembly before the slider bar — depending on the sight design. The reference is the string and the rail directly, not the sight itself. Get the string and the slider rail into the same plane. Ignore anything else on the sight at this stage.
Tilt (second axis)
Once the slider rail is set, the bubble housing needs to confirm that reference. The bubble is moved with the housing — it is not a separately rotatable capsule. Adjusting tilt (second axis) means rotating the scope housing until the bubble reads centered when the slider bar is perfectly level.
Tilt is complete when the bubble reads centered with the slider bar at perfect level.
When tilt is off, the sight plane and the arrow plane are not in sync. The archer is using the bubble as a level reference, but the reference has drifted from true. The arrows go where the bow actually is; the bubble is reporting something else.
To shoot in your tilt: zero at close range, then slide the sight housing down to the 60 or 80 yard position without changing your windage, and check where the impacts land. If windage drifts as you move the housing, tilt is off. Adjust and repeat until moving the housing up and down produces no windage change.
Optional confirmation method: rest the bow on the ground, string down, and level an arrow nocked in the bow. If the arrow is perfectly vertical, the bubble should read centered. If it doesn't, tilt needs adjustment.
Bow cant and tilt: two parts of one axis
Both adjustments address the same rotational degree of freedom — the roll of the bow around the line of sight. Bow cant (first axis) establishes the physical reference. Tilt (second axis) calibrates the bubble to confirm it. The traditional names make this sound like two independent axes. It is not.
Shooting with a deliberate cant is fine. The sequence still works: set the slider rail to whatever angle you intend to hold, then calibrate the bubble to read centered at that angle.
The cost of a canted bow is not slope-dependent. The visual line from your eye through the sight is not aligned with the arrow's line of travel. Zero at 15 yards, and the arrow will be off at 100 — the arrow is traveling in a direction the sight line is not quite tracking. The two planes diverge slightly. The effect is small, but it compounds with distance.
Scope yaw (third axis)
This is the adjustment as viewed from above.
Imagine you mount a laser to your scope housing. When the scope is pointing correctly toward the target, the laser points there too. Now rotate the scope housing to the left — adjust the scope yaw. The laser, mounted to the housing, now points well to the left. But the pin, which is just a reference point inside the housing without a direction of its own, still appears to sit in the center of the scope. Scope yaw (third axis) is adjusting that imaginary laser pointer. The pin cannot tell you which direction the housing is actually facing. The laser would.
When scope yaw is off, there is no effect on level ground. The problem only appears on angled shots — uphill or downhill — where the yaw causes the bubble to misread, the archer rolls the bow to re-center it, and that roll pushes the pin sideways. The steeper the angle, the larger the error.
One important consequence: adjusting scope yaw moves your windage zero. Every adjustment changes where the pin sits relative to flat-ground impact. You must re-zero on flat ground after any scope yaw adjustment before the results on a slope mean anything.
Scope pitch
The same idea as scope yaw, but in the vertical plane — tilting the face of the scope upward or downward.
When the scope face tilts downward, it introduces inconsistencies that change with distance and can produce optical errors when using magnification. It is not a simple constant offset that zeros out cleanly across the full range.
The more practical danger is drift. Scope pitch can shift over time as the sight settles or fasteners loosen, and if it drifts, it pulls your pin positions with it. Verify it periodically rather than treating it as a one-time setup step.
Some manufacturers design the scope mounting point to be in line with the optical reference, which removes scope pitch as a variable. If yours does, you can treat it as stable. If yours does not, it is worth checking when you notice unexplained pin drift.
Setting them in order
The order is not optional. Each step establishes the reference the next depends on.
Step 1. Bow cant (first axis)
Level the string and the slider rail directly together, ignoring the sight itself. The goal is that the string and the rail are in the same plane. Alternatively: kick the string out of the way and level the slider rail on its own. Get this right before touching anything else.
Step 2. Tilt (second axis)
Adjust the bubble in the scope housing until it reads centered with the slider bar at perfect level. Shoot it in: zero at close range, then slide the housing to the 60 or 80 yard position and check windage. If it drifts, adjust and repeat. Optional check: bow on the ground string down, arrow nocked and perfectly vertical — the bubble should agree.
Step 3. Scope yaw (third axis)
Dedicated jig tools exist, but they carry enough of their own mounting error that shooting is simply more accurate. Zero on flat ground first. Then find a steep uphill or downhill shot and observe where the arrows land.
If windage is off on the slope, adjust the housing in the direction that corrects it. But every adjustment to scope yaw moves your zero. You cannot go straight back to the slope and compare — that result will be invalid. You must re-zero on flat ground after every adjustment before returning to the slope. Skipping that step means you are comparing against a zero that no longer exists.
The loop is: zero flat → shoot slope → observe → adjust → re-zero flat → shoot slope again. Each iteration requires a fresh flat-ground zero.
Step 4. Scope pitch
Set at mounting. Verify at distance. If your sight's mounting point is not in line with the optical reference, check for drift periodically — scope pitch can pull your pin positions over time as fasteners settle.