The Benefit of Pendulum Bow Sights

My first bow was a hand-me-down PSE that my older brother bestowed upon me in the late 90s. The model was from the previous decade, equipped with a Keller pendulum sight. To me, that was the highlight of the entire rig.

The genius behind pendulum bow sights is that the single pin, no matter if you tilt the bow up or down while you’re from an elevated position, moves to stay fixed on your target. That’s one pin for all distances within 40 yards with no guesswork. For a youngin’ learning the ropes, that was invaluable.

While I never harvested a deer with that old bow, I learned the fundamentals I still use today. I ended up switching to a multi-pin sight on my next compound. Even after practicing all summer, I missed my first few deer that season. It didn’t take long until I upgraded to a TruGlo pendulum, and wouldn’t you know it, I harvested my first deer, a spike, not long after.  

Nowadays, most bows shoot fast and flat, so often a single pin may be consistent out to 30 or so yards. However, if you’re hunting from a stand, you still need to compensate for the elevation. Even if your arrow can be off, by a hair, it’s enough to cause a miss or worse, a wound animal.

The Science

It all comes down to gravity and angles. When you’re shooting your bow at ground level, the force of gravity on your arrow in flight is the strongest because it’s parallel to the Earth. Once you’re in the tree, your arrow’s trajectory has changed, and it’s now at an angle with lower forces of gravity affecting it. Due to this, if you sight your bow in on the ground, your arrow impact will be slightly higher when treestand hunting. Many hunters remedy this by bending at the waist, not their bow arm, until their pin is on their target, which means your form is close to the same as it is when you’re shooting from ground level.

While hunting from a treestand, a right-angle triangle exists between your bow, the ground and the deer. The Pythagorean theorem tells us that a right-angle triangle consists of two legs that meet at a 90-degree angle, and the hypotenuse, which is the longest side of the triangle. The hypotenuse is the line your arrow will take to make contact with the deer, while the 90-degree angle is the base of the tree you’re in.

Assume your treestand is 20 feet high and there’s a deer 30 yards away. While the horizontal or true distance is indeed 30 yards, since you’re elevated, the line of sight or linear distance is a few yards farther. The true distance between you and the deer hasn’t changed, but the higher you get in the tree, the linear distance will increase and so will the affect of gravity on your arrow. Since a pendulum sight swings as you tilt your bow, it works a function of trigonometry that will adjust to the correct yardage without you having to bend at the waist.

Benefits of Using a Pendulum Sight

For multi-pin sight users, these subtle differences in distance are important to note. If you’re using a reading from a range finder of the linear distance, your arrow will hit high or you’ll miss. If your bow was sighted in on the ground level and you’re treestand hunting, you may also hit high. To remedy this, while you’re in your treestand, you need to range the trunks of trees that are eye level to you, which will provide the true distance. There are also tilt-compensated range finders on the market capable of making the calculations for you, meaning you can range objects on the ground from an elevated position.

However, if using a pendulum sight, you need not worry about these variations. The pin swings to stay perpendicular with the ground as you tilt your bow. This results in an accurate shot while treestand hunting at distances up to around 40 yards.

For those that use a rangefinder and a multi-pin sight, there will come a time when you are faced with a shot and you’re unsure of the distance. You may not have time to get an accurate yardage reading. What do you do? The ethical thing is to not shoot and wait for a better opportunity, if you get one at all.

With a pendulum sight, as long as you have marked a 40-yard radius around your stand, you know you can make an accurate shot within that distance with a single pin. Beyond 40 yards is typically out of range, but this depends on the speed of your bow. However, most hunters stay within that yardage to begin with, as farther distances can result in a wounded animal. Even if you’re shooting from ground level, you can lock the sight in place so that it doesn’t swivel, acting as a fixed, single-pin sight.

These sights aren’t as popular as they once were in the 90s, with TruGlo being one of the only major manufacturers offering a model. But, they’re still used by plenty of hunters. For younger hunters, using a pendulum is an effective way to introduce them to bowhunting while they’re learning the basics.