Rangefinder Binoculars – How Do They Work?
What are Rangefinder Binoculars and How Do They Work?
If you know the height of an object, such as a hill or navigation marker (often printed on navigation charts), and can measure the angle to its top using binoculars equipped with a rangefinder reticle, you can calculate your distance from that object.
Many of the best marine binoculars come with a reticle rangefinder, that enable those aboard boats, yachts and other marine vessels to calculate the distances
What is a Rangefinder Reticle?
A reticle (or reticule) is a net of fine lines or fibers in the eyepiece of the binocular, monocular, microscope, scope or other optical device used for sighting and taking other measurements.
Rangefinder reticles are obviously used to calculate the distance between you and an object you are observing, but can also be used to calculate the height of an object or the included angle of a viewed object.
How do Rangefinder Reticles work?
There are several systems used to calculate the distance by rangefinder reticle binoculars and scopes. The simplest and most commonly used system involves comparing a scale or measuring marks on the reticle in the binocula field-of-view against a known sized object that you are looking at. The military and hunters refer to this as the Mil-Dot reticle and the formula is known as the Mil-dot formula:
Take the height or length of the object, then calculate the distance away from that object using simple math. You can also calculate the height or length of the object if you know the distance that you are away from it.
If you are on your boat and look through your reticle rangefinder binoculars at a house that you knew to be 30 feet tall, and the scale height on the reticle rangefinder reads 40:
Distance = (Height of House / Scale Height) / x1000
= (30′ / 40) x 1000
Distance to the house = 750 feet
Do Rangefinder Reticles Work?
Yes, but in terms of providing an exact distances, they aren’t as accurate or fast as a laser rangefinders, but they can give you a good idea and work over long distances.
How accurate they are depends on the user lining up the target and of course how accurate you are when estimating the height or length of the target. If you know the exact height of the target and line it up very carefully on the reticle, they will be very accurate.
For boating binoculars and other marine uses, reticle rangefinders are in most cases the best solution.
Related Articles from The Lake Life:
- Rangefinder Binoculars – How Do They Work?
- Top Rated Marine Binoculars
- About Binoculars
- Bird Watching Binoculars Buying Guide
- Marine Binoculars Buying Guide