Western Hunting Journal, Premiere Issue whj001_premiere - Page 33

Parts of a Rangefinder Small, powerful processors and advanced components have allowed modern rangefinders to become incredibly accurate, compact and easy to carry. EYEPIECE LENS ROOF PRISM LCD As I watched the bull feed out of the trees into the open hillside, I didn’t have to estimate the distance or guess what adjustment to make. A quick check with my rangefinder told me everything I needed to know. He took two more steps; I checked again to confirm the reading, quickly referenced the ballistic informa- tion for my rifle, and fired a single shot. The bull never took another step. Without question, rangefinders play one of the most important roles in consistently placing shots on target, and when it comes to hunting, bullet place- ment is the key factor in ensuring swift, ethical kills. Knowing the exact distance to targets allows for pre- cise adjustments and compensation, or perhaps rul- ing out a shot all together. I can say with one hundred percent certainty, regardless of how large the bull was, had I not known the distance in that situation, I would have never even attempted a shot. The risk of potentially wounding an animal due to a misjudged shot is simply too great a risk to take. What to Look For OBJECTIVE LENS LIGHT-EMITTING LASER DIODE LIGHT-EMITTING PHOTODIODE LIGHT-RECEIVING LENS Beam Divergence Over Distance Similar to the beam of a flashlight, the beam divergence of the laser will spread over distance, affecting the ability to accurately read targets. Units 1,000 yds rated for longer ranges will have less divergence, allowing accurate readings at great distances and 500 yds with less interference from the target surroundings. 1,500 yds While few will argue the importance of a quality rangefinder, the myriad of styles, features and options available can leave many feeling overwhelmed and confused. Let’s get started with a quick breakdown of what to look for, and maybe also dispel a few com- mon misc onceptions. Typical rangefinders work by emitting a class 1 (in- visible) laser which reflects off the desired target and the returning signal is read by high speed sensors in- side the unit. Using the known speed of light, proces- sors in the unit can then calculate the time it took to receive the return signal, and then convert to distance traveled. The process seems relatively simple, yet it is anything but. reflected signals, in turn produce faster and more ac- curate readings. Processor Size of Laser Beam Just like computers or phones, some units employ processors that are faster and more powerful than others. When it comes to rangefinders, this means some units can compute more readings, faster read- ings, and calculate faster data than other units. Early generation rangefinders often based readings off a single return signal, which often resulted in errone- ous readings, whereas newer units commonly emit pulses of signals that return more data back to the unit allowing for tighter averaging calculations and a much more accurate readout. The key to getting an accurate readout is doing your best to control what data is being sent back to the machine. Looking at units in a store you can quickly see a variety of aperture sizes. Generally, larger apertures can better collect larger amounts of Have you ever noticed how a flashlight beam on your living room wall may be a small spot, but it can illu- minate your neighbor’s house across the street? The beam coming out of a rangefinder acts much the same way. The divergence, or spread, of the beam can vary greatly from one unit to another. Some units will state what this may be, while it can be hard if not impossible to find on others. Basically, as the beam spreads over distance, it may be picking up readings from objects that are not the target. When these read- ings return along with the target readings, the unit may average all the readings and give a false distance. Sometimes, if the target is small enough, and there is a lot of surrounding interference, you may not get a target reading at all. Too tight of a beam can also cause problems, as at longer distances, it may be diffi- www.westernhuntingjournal.com 31