Use of Binoculars


One important word of caution – NEVER look directly at the sun through binoculars (or a telescope). Doing so could cause permanent eye damage or blindness!

Parts of the Binoculars:

labeled binoculars Become familiar with your binoculars and their parts. In your lab notebook, draw a picture of the binoculars you are using and label the following, underlined parts.

    binoculars in case
  1. Obtain the binoculars that correspond to your assigned seat number.
  2. lens caps left in case
  3. Place the lens caps back in the case, and put that back in the drawer until you are done.
  4. binoculars with strap wrapped
  5. Note that the neck strap is (hopefully) coiled neatly around the binoculars. You are expected to make sure the strap is neatly coiled and the lens caps replaced each time you put the binoculars away after use.
  6. The barrels are the main body of the binoculars and contain prisms that reflect the light from the objective lenses to the ocular lenses. Note that the barrels are hinged together at the center.
  7. 7×35 and 7×50 comparison
  8. The objective lenses are on the “front” of the binoculars – note that these are 35 mm across. These are achromatic lenses (a- = not, without; chromo = color) which are made of several layers of glass bonded together to prevent “rainbows” of color while looking through the binoculars. They are also coated with a substance to help transmit light better. Binoculars also come with 50-mm objective lenses, which let in more light, thus are better for observing under dimmer light conditions. Here, the two sizes are compared.
  9. The ocular (ocul = an eye) lenses (eyepieces) are mounted on the ends of the barrels closest to your eyes. The oculars can be moved closer together or farther apart to adjust to the width of your eyes by bending the hinged center of the binoculars. Practice flexing this hinge.
  10. interpupillary distance scale
  11. Note the interpupillary distance scale on the central joint of the binoculars. This indicates the distance between your eyes (70 to 80 mm).
  12. diopter scale
  13. To the side of the right ocular there is a scale, the diopter scale, – you will use this to customize the focus to your eyes.
  14. center wheel
  15. The center wheel is used to focus the binoculars.
  16. prisms and light path
  17. Inside of the binoculars where you can’t see them are several prisms. These are used to redirect the incoming image to your eyes. If you drop the binoculars or bang them on something, you may jar the prisms out of position, in which case you will no longer be able to see properly when attempting to use the binoculars. Thus, it is very important to take good care of the binoculars and not drop them or bang them on something.

Use of the Binoculars:

  1. Put the strap around your neck and, while on field trips, also hold the binoculars so they don't swing. Avoid dropping or banging the binoculars! Please keep your fingers off the lenses. If there are fingerprints on the lenses, clean with your breath and lens paper, being careful to not scratch lenses with gritty dirt.
  2. interpupillary distance scale
  3. Adjust the interpupillary distance to suit your eyes by bending the center hinge of the binoculars – note the interpupillary distance scale reading and record in your notebook (which setting lines up with the dot?).
  4. center wheel
  5. Find some object upon which to focus and use the center wheel (which focuses both oculars together) to adjust the focus so that it is correct for your left eye.
  6. diopter scale
  7. Note the dot on the right eyepiece. Line up the “0” mark of the diopter scale with this dot, then rotate the right ocular to adjust the diopter setting until the right eye is in focus, too. Note/draw where on the +/ scale the dot falls. Record in your notebook for future reference.
  8. If not already done, record numbers from scales so that next time you use the binoculars, you can quickly adjust them to your needs by setting to the appropriate numbers.
  9. Now that the binoculars are set for your eyes, use only the center wheel to focus on whatever you wish to see.
  10. Practice focusing on several targets (first stationary then moving) such as tree branches, birds, etc. to familiarize yourself with use of the binoculars.

Storage of the Binoculars:

    binoculars with strap wrapped
  1. Wind the neck strap NEATLY and securely around the center of the binoculars so that it holds itself in place.
  2. Flatten the binoculars and use the center wheel to move the oculars all the way down if needed so that the binoculars fit into the drawer.
  3. binoculars with lens caps on in case
  4. Place the lens caps on the lenses of the binoculars. Double check to make sure you have done all of these things before putting away the binoculars.
  5. binoculars in case
  6. Carefully put away the binoculars. Return them to their case prior to returning them to the drawer.
  7. binoculars in drawer
  8. Place the binoculars/cases in the drawer in numerical order.

Other Things to Include in Your Notebook

Make sure you have all of the following in your lab notebook:

Copyright © 2010 by D. B. Fankhauser and J. Stein Carter. All rights reserved.
Based on printed protocol Copyright © 1982 D. B. Fankhauser
and © 1993 J. L. Stein Carter.
This page has been accessed Counter times since 18 Dec 2010.