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strap through the underside of the friction clip, over the clip bar, and out. Then carefully pull the 
strap tight to eliminate the loose loop. Refer to the pictures at left. Certain waterproof and shock-
resistant binoculars feature a deluxe wide strap. The ends, however, are the same as those 
described here. 

 

 

How to use your binoculars:

 

 
Your National Geographic binoculars are premium-quality optical instruments designed to provide 
many years of reliable service. To customize your binoculars for the highest level of performance, 
we recommend that you make the following simple adjustments. 

 
 

Interpupillary distance: 

 

Interpupillary distance is the distance from the center of your 
left eye to the center of your right eye. The distance between 
the centers of the two eyepieces of your binoculars should be 
the same. You can adjust this distance by squeezing the two 
binocular lens barrels together or by pulling them apart.  

 
 
1) 

 

Make this adjustment while you are looking through your 

binoculars at a subject that is more than 100 feet away. 
 
2) Focus the eyepieces until you can clearly see your chosen subject. Do not be concerned if 
your focus is less than perfect.  The next procedure will optimize your focus. 
 
3) If the eyepieces are too far apart, you will see two distinct image circles. Squeeze the lens 
barrels together until the two image circles merge into one circle. 
 
4) 

  

If the eyepieces are too close together, the two image circles will overlap. Slowly move the two 

lens barrels apart until the two image circles appear as one. 
  
 

Focusing: 

 
The National Geographic binoculars have either a center focus wheel or eyepieces that can be 
adjusted individually to obtain the best focus.  
 
Center focus wheels adjust both eyepieces at the same time. The wheel is located between the 
barrels. To adjust the focus, aim the binoculars at a distant object and turn the wheel until the 
image is clear and sharp in the left eyepiece. To focus the right eyepiece, follow the steps below. 
 
 

Diopter Adjustment: 

 

Since one eye is usually slightly stronger than the other, your center 
focus binoculars feature the Diopter Adjustment

 

to compensate for this 

difference.  
 
1) 

  

During daylight, view a subject from at least 100 feet away. 

 
2) 

 

Close your right eye, but refrain from squinting.  

 

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