How do I use the distance and size calculator on my Oceana binoculars? How accurate is it?
Your Oceana binoculars have a built-in etched ruler or reticle in the optical system to allow you to measure angles in the field of view. Once you measure an angle, you can use that number with the calculator on the objective lens barrel to figure out either a distance (if you know the size or height of what you’re looking at) or the size (if you know the distance to the ship, rock or building). First, you measure the angle with the reticle. The binocular reticle has vertically numbered divisions 1 to 4 and 1 to 2 on each side of the middle horizontally. Unnumbered divisions are 0.2. Each of these can be estimated to tenths. Transfer the number to the calculator by turning the dial, placing the number under the ANGLE index mark. For finding distance if size is known, look on the OBJECT SIZE scale for the number that is the known size of the ship, building, etc. Mentally add zeros as needed, since the scale is numbered from 1 to 10. Look directly under this number on the DISTANCE scale for the distance, adding the same number of zeros (if any) you added to the OBJECT SIZE. For finding size if distance is known, transfer the number to the calculator dial under the ANGLE index mark. Look on the DISTANCE scale for the number that is the known distance of the rock, building, etc. Mentally add zeros as needed, since the scale is numbered from 100 to 1000. Look directly above this number on the OBJECT SIZE for the size, adding the same number of zeros (if any) you added to the DISTANCE. Besides your ability to measure in the reticle, what your range accuracy is also depends on how big the ship or object you are looking at is and how far away it is. For example: A thousand-foot container ship measuring 0.2 would be 275,000 feet away. Measuring at 0.22 it would be 295,000 feet away. The same ship measuring 2.0 would be 27,500 feet away and measuring 2.02 would be 27, 750 feet away. The same is true for size – accuracy not only depends on your measurement, but also depends on distance and size. Intuition and the example agree: a closer or larger object will be easier to measure for an accurate distance or size.
Created On: Nov 18 2008 11:48 AM