Seamanship_Secrets_185_Tips_-_Techniques_for_Better_Navigation-_Cruise_Planning-_and_Boat_Handling_Under_Power_or_Sail_(Re)_e..

easy calculations and adjustments 61

FOCUS ADJUSTMENT CHOICES
Binoculars come with center focus or individual focus eyepieces. Center
focus makes adjustment easier and readjusting unnecessary as your viewing
range changes. Many fine professional marine binoculars, however, come
with individual focus lenses. They just take a bit longer to adjust and need
readjustment at different ranges.
Take the time to learn the adjustment process for both types of instruments. Now
you can select the perfect pair that will give you satisfaction for years to come.

How to Adjust Individual Focus Eyepiece Binoculars

1. Focus the left eyepiece. Close your right eye or cover the right
   objective lens. Focus the left eyepiece on an object at least 1 mile away.
   Mark the scale setting between the body and the focus ring.


2. Focus the right eyepiece. Close your left eye or cover the left objective
   lens. Focus the right eyepiece on a distant object at a range of at least
   1 mile. Mark the scale setting between the body and focus ring.


3. Reset the focus when ranges change. With individual focus settings,
   you’ll need to make incremental adjustments when viewing objects at
   longer or shorter distances than your original setting. Remember to
   reset your binoculars back to your personal focus-ring setting.

How to Adjust Center Focus Eyepiece Binoculars

1. Focus the left eyepiece. Close your right eye or cover the right objective
   lens. Use the center focus wheel to focus the left lens while viewing an
   object at least 1 mile away. Mark the scale setting on the center focus ring.


2. Focus the right eyepiece. Close your left eye or cover the left objective
   lens. Using the right eyepiece focus ring, adjust the focus by viewing
   the distant object. Mark the scale shown on the body and focus ring.


3. Fine-tune with the center focus ring. When you need to make
   adjustments as viewing ranges change, use only the center focus ring.

How to Adjust a Sextant in Th ree Steps

Any cautious navigator will see the sense of carrying a sextant and

double-checking the GPS ...

—John Vigor, The Seaworthy Offshore Sailboat

Long before GPS, the Coast Guard used sextants to position buoys and lights
to a tolerance of +/−10 yards. With a bit of practice, it’s easy to use a sextant
for finding your position or your distance off an object in piloting waters. Out
at sea, celestial navigation remains the primary backup to GPS. The sextant
requires periodic maintenance, like any fine instrument.