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How Do I Use Binoculars?

Being able to clearly see elephant seals is vital to the success of your students' field trip. Students prepare for upcoming field trip by becoming familiar with binocular structure and use.

Time required: time varies Location: in class and/or sections at Bear Valley Visitor Center Suggested group size: entire class Subject(s): physics Concept(s) covered: binocular structure and use Written by: Christie Denzel Anastasia, National Park Service Last updated: 09/31/00

Stucdent Outcomes
At the end of this activity, the students will be able to:

• Understand the structure of binoculars.



• Practice focusing on moving images with binoculars

California Science Standard Links (grades 6 – 8)
This activity is linked to the California Science Standards in the following areas:

6th grade:

7b - appropriate tools/technology to perform tests, collect/display data

7th grade:

6b - to see an object, light emitted/scattered must enter eyes
6d - simple lenses used in optics
7a - appropriate tools/technology to perform tests, collect/display data

National Science Standard Links (grades 5 – 8)
This activity is linked to the National Science Standards in the following areas:

• Content Standard A - Abilities necessary to do scientific inquiry: use appropriate tools and techniques to gather, analyze, and interpret data.

Materials
To be provided by the teacher:

• 1 - 15 pairs of binoculars

Afailable for checkout at Bear Valley Visitor Center or use at Clem Miller:

• Elephant Seal Kit

Procedures
Note: This lesson can be done in various stages depending on whether or not students have access to binoculars in class.

• If students can bring in a pair of binoculars to use in class:
  This entire lesson can be conducted in class.
• If students can share a pair of binoculars to use in class:
  Procedure 1 and 2 taught to entire class. Student teams can experiment with binoculars in 10-minute intervals throughout day.
• If students do not have access to binoculars:
  Procedures 1 and 2 can be conducted in class, Procedure 3 at Bear Valley Visitor Center when students receive individual binoculars from the Elephant Seal Kit.

1. How do binoculars work?
   In Theory: Before prisms were available, lens barrels had to be very long to increase the distance between eyepiece lens and objective lens to achieve magnification. These are the traditional "pirate scopes". With the introduction of prisms, the light could be bent and barrels made shorter. Binocular vision allows two images to become one for depth perception. Monoculars are like binoculars, but made for one eye and provide no depth perception.
   
   In Structure: There are four main components of binoculars. Power is a function of these components. A 6 5 30 binocular has 65 magnification and a 30-millimeter lens. A larger lens lets in more light.
   Eyepiece lens: there are several convex lenses here for magnification. This is the lens closest to your eyes.
   Prism: Bends light rays and returns reverse image to normal. Lens barrel: Keeps distance between eyepiece lens and objective lens; blocks side lighting and protects from dirt. Objective lens: Gathers light in a convex lens. This is the lens that has a millimeter measurement (i.e., 6 5 30).

2. How do I get binoculars to work specifically for me? Taking care of binoculars:
   • Always keep them attached around your neck so they arenŐt accidentally dropped.
   • While you are focusing binoculars, stand still. It would be easy to fall while focusing and walking.
   • Clean binoculars properly.
   If you wear eyeglasses:
   • Keep your eyeglasses on.
   • There is usually an "eye cup" rubber piece that folds back where your eyeglasses meet the eyepiece lens.
   Things you adjust once:
   • Barrel distance: The two barrels can be moved closer or further apart depending on the distance between you eyes.
   • Right eyepiece focus: There is a knob on the right eye piece that corrects for visual differences between your two eyes. If you are seeing more than one image, adjust the right eyepiece until there is one image.
   Things you need to adjust with each observation:
   • Center focus: Adjust the center focus with each observation to bring image into view.
   Focusing on an image:
   • Adjust barrel distance and right eyepiece
   • Locate the image with your eyes. Are there any landmarks or reference points next to the image? These may help you find the image using the binoculars.
   • Focus your eyes on the image. Without looking down, place the binoculars directly in front of your eyes. The rubber cup surrounding the eyepiece lens should rest against your eyebrow (unless you are wearing eyeglasses).
   • Focus image into view with center focus.
   • Keep elbows tucked in close to your body and both hands on binoculars to avoid a shaky image.
3. Practice using binoculars.
   Focus on a stationary object.
   Pick an object that doesnŐt move. Choose one near and one more distant. Use center focus.
   
   Focus on moving objects in class.
   Right/ left: Have a student walk slowly across the classroom while students use binoculars to keep in view. Speed up student walker to add a challenge.
   
   Away/ toward: Choose a student to move toward and away binoculars. Discuss range that binoculars will work. At some point, the object is too close to focus.
   
   Focus on multiple moving objects at school.
   Attend a sporting event or practice at a lunch session in the cafeteria. Place a wildlife poster on a piece of cardboard and stick. Have a student move around the classroom with the posterboard: slow, fast, up, down, toward, away.
   
   Focus on wildlife.
   Bring class outside in an area where they are likely to view moving wildlife such as birds

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