Sunday, May 17, 2020

How to use binoculars for bird watching

Your binocular is your most important tool for watching birds. If they are not set up correctly you will not see birds well. Worse, you may strain your eyes and give yourself a headache. That's why you need to have a good pair of binoculars and adjust them for your eyes.

This article tells you how to properly adjust your binoculars so they are calibrated for your eyes and give a sharply focused image. Then we'll discuss some techniques for using binoculars that are specific to watching birds.

Every time you pick up a new pair of binoculars you must adjust 4 things to use them properly:
  1. eye cups
  2. barrels
  3. focus
  4. diopter
After these 4 items are adjusted properly, you'll only need to adjust the focus afterward to view birds.

Once your binoculars are properly adjusted I will explain how to use binoculars to find more birds and get better views. I'll explain:
  1. aiming binoculars
  2. holding binoculars
  3. holding steady
  4. scanning: finding hidden birds

Here is a photo showing the external parts of a binocular:
Image of binoculars with labels

How to properly adjust your binoculars


If you haven't used binoculars much, especially for birds, it can take a bit of getting used to. Adjusting binoculars becomes second-nature for experienced users. Once your binoculars are adjusted for your eyes, then only the focus needs adjusting when viewing birds. The other settings will stay the same and not need readjusted unless they are moved. If you share a pair of binoculars, however, you'll constantly have to readjust them. So it is best if each person has their own pair.

1. Adjusting the eyecups


Many people wonder whether they can wear eyeglasses when using binoculars. Yes you can!

If you are only far sighted or near sighted, then you may be able to use binoculars with your eyes only. That would actually be ideal. However, most people who wear glasses also have astigmatism--their eye lenses aren't perfectly round and have to be corrected. So they (and, yes, I) must wear eyeglasses to see properly with binoculars.

Binoculars have a specification called eye relief that allows users to wear eyeglasses or not. A longer eye relief is better for eyeglass wearers. Look for a spec of at least 15.5 mm or longer. If the eye relief of the binocular is 15mm or less you won't be able to see the entire field of view with eyeglasses--the edges will be cropped from view.

To fix this loss of field of view, you need to get your eyes closer to the binocular ocular lenses. You do this by retracting the binocular eye cups.

On the other hand, with no eyeglasses, you can get your eyes too close to the binocular lenses. Then you'll see black circles in the middle of your binocular field of view. You need to move your eyes back away from the lenses. This is accomplished by extending the binocular eye cups.

Adjusting the eye cups is easy. They fold down or up or twist in or out. If you wear eyeglasses, then the eyecups should be twisted in so that the binocular ocular lenses are closer to your eyes. If you don't wear eyeglasses, then the binocular ocular lenses need to be farther from your eye. Twist the eyecup out, pushing your eyes away from the binocular ocular lenses.

Folding rubber eye cups are either up or down. Twist type eye cups may have indents to select mid-points between fully up or down.

If you don't wear eyeglasses, the binocular eyepieces (eyepieces are the ocular lenses and eyecups combined) rest on your eyebrow and cheek. That is the outer eyepiece casing, not the actual lenses themselves.

The eyepieces (eye cups) of the binoculars rest on your eyeglasses if you wear them. I find that the binoculars push my glasses up my nose and closer to my eyes. The view is fine. But my eyebrows leave an oily smudge on my glasses afterwards. It doesn't interfere with my ability to see using binoculars. But when I'm done bird watching I need to clean the eyebrow smudges from my glasses.

Another problem with eyeglasses is that they can fog over in cold or humid weather when using binoculars. This is especially troublesome when wearing medical face masks during pandemics! Sigh. (I truly hope you're reading this in the future and don't have any idea of what I'm talking about.)

I hate eyeglasses.

2. Adjusting the width of the binocular barrels


Everyone's eyes are a different width apart. This is called the interpupillary distance. For adults, the average interpupillary distance is about 65mm. Most binoculars adjust from 56-72mm. Binoculars for children usually adjust down to 50-52mm and are suitable for children "7 years or older." Children often can't properly see out of adult binoculars.

Thus, the barrels of the binoculars must be adjusted for the width of each observer's eyes. Fortunately, this is easy. The two barrels of binoculars are connected with a bridge. The barrels pivot on a central hinge.

Grasp the barrels firmly in each hand while bringing the ocular lenses up to your eyes. Push or pull to adjust the width of the binoculars so that both eyes see a single view. You should have a clear single circular view without any black crescents.

If you are seeing double images, then the barrels are not lined up properly. Change the width of the barrels to see if this helps. Collimation refers to the factory adjustment that makes the two barrels parallel. Internal prisms may be jarred out of alignment if binoculars are dropped. Collimation may also be poor on cheap binoculars. Usually binoculars must be returned to the factory for repair, if this is the case.

The hinge should be stiff so that the binocular barrels keep their distance. They shouldn't flop together or apart. On the other hand, they shouldn't be so stiff that they are hard to move.


Image of binoculars with diopter ring labeled

3. Adjusting the focus of the left eye


Most binoculars have a focusing knob or wheel on the bridge near and between the eyepieces. These are adjusted while looking through the binoculars.

Select a target object to look at, perhaps about 100 feet away.

Grasp the binoculars firmly with both hands and raise them to your eyes. With your index finger turn the knob one way or the other until you can clearly see your target object with your left eye. If it helps, place the large lens cap over the right objective lens (the "big end"). Do not squint your right eye closed, as that changes the shape of your eyes too much.

Once the left eye is in focus we move on to the right eye. Remain in place. Don't move the focus knob. Follow the next directions.

4. Adjusting the diopter of the right eyepiece


There is an adjustable ring around the right eyepiece (or sometimes in the center of the bridge near the focus knob). This is the diopter adjustment. It adjusts for differences in focus between your eyes.

If you don't set the diopter correctly, your image will appear blurry. One eye or the other will not be in focus.

Look again through your binoculars at your target object. Make sure it is still in focus with your left eye. Now, adjust the diopter ring by twisting it left or right until the right eye is equally and comfortably in focus. You should have both eyes in focus with no eye strain.

Verify that you have the correct calibration by choosing near and far objects on which to focus. If you have to, readjust the diopter. From now on the focus knob will move both eyepieces and they should remain in proper calibration. Birds should be in focus with both eyes whether near or far. Now you are ready to spot some birds!

Many diopter rings have a marker and a + or - mark as well as a 0 in the middle. These marks are on diopter rings on the underside of the eyepieces. Take note of where you have adjusted the diopter (toward the + or -). This diopter placement should be in the same place whenever you use the binoculars. Some binoculars have a locking mechanism to keep the diopter setting from accidentally moving.


Here's a brief but excellent video from Cornell Lab of Ornithology showing how to make these binocular adjustments and how to aim your binoculars.



How to use bird watching binoculars


I'm going to break this into two parts. First, we'll discuss how to get a clear view of a bird that you have spotted with your bare eyes. Second, we'll talk about some techniques to use your binoculars to look for hidden or distant birds.

Aiming: Spotting birds in your binoculars


Newer birders sometimes have a bit of trouble spotting birds through their binoculars. With a bit of practice, though, you'll soon lift your binoculars and have the bird centered in view immediately.

The key is to look at the bird, not at the binoculars. Here's the technique for spotting birds in your binoculars.

With your bare eyes, turn your body so that you are looking straight ahead and viewing the bird. Keep looking at the bird. Now--without looking at the binoculars--bring them up to your eyes. The bird should appear in view. Adjust the focus to bring the bird into view.

Many beginners look away from the bird and at the binoculars as they bring them up to their eyes. Thus they have more difficulty quickly locating the bird in the binoculars. Don't look at the binoculars while bringing them to your eyes--keep looking at the bird!

Practice with birds flying in the sky until you can "get on them" every time.

How to hold binoculars


Holding your binoculars properly will make it easier to spot birds and keep your arms from becoming fatigued quickly.

The proper way to hold binoculars is each hand holding the separate barrels. Four fingers should go over the top of each binocular barrel. Your thumbs go under the binoculars. Rest your index fingers on the top sides of the focus wheel.

This hand posture should keep the binoculars well-balanced. Different makes and models and sizes may feel more or less well balanced, depending upon the size of your hand and length of your fingers. This is a personal preference to test out, if possible, when deciding which pair of binoculars to buy. You should place your hands so that the binoculars are not overly heavy at the front or back.

Image of binoculars held properly in hands
Proper way to hold binoculars

Holding your binoculars steady


The more magnification your binoculars have, the harder it is to hold them still. They magnify any hand shakiness. The longer you hold your binoculars up to your eyes, the more wearisome and shaky your arms become.

If you are outside and it is windy, you will have an unsteady view, too.

There are a few things you can do to hold your binoculars steady.

When holding your binoculars do not hold your elbows out to the side. Instead, hold your elbows down so they are resting on your ribs. This will steady your binoculars and keep your arms from tiring quickly.

If you are looking at one bird for a prolonged time, bring your hands forward toward the eyepieces. Brace your index finger against your brow ridge (if wearing eyeglasses). Or, brace your thumb against your cheek.

If you are able to sit on the ground, try this. With your knees drawn up, brace your elbows on your knees.

You can also brace yourself against a firm unmoving object. Lean your binoculars or elbows against a corner of a house, against a tree, against a vehicle, or on top of a fence post. All these will give you a less shaky view and reduce arm fatigue.

Image showing improper way to hold binoculars
No! Elbows out, wrist bent
Image showing proper way to brace binoculars
Yes! Elbows down, wrists straight

Scanning: Looking for birds with your binoculars


Primarily you look for birds with your bare eyes. When you spot something, you then look with binoculars. Why?

It is because your eyes have a very wide field of view. Most humans have a horizontal field of view of 210 degrees. Even binoculars with a wide field of view barely see 8 degrees. You can easily notice bird movement out the "corner of your eye," away from your central view.

However, there are times when you can scan with your binoculars to look for birds you would not otherwise see.

You can scan the horizon for birds in several circumstances.

Scan the edges of a riverbank or pond--all away around, if you can. There are often birds on the edge of the shore, wading, or swimming near the shoreline.

Scan a distant tree line or ridgeline for hawks perched in trees.

Scan the horizon when looking out to sea from a sea watch or from a boat at sea.

Scan the sky against overcast clouds when searching for high-flying swifts or hawks. This is especially productive if your are in the mountains or visiting a known hawk watch site.

Scan down fence lines and fence posts. Scan down power lines and utility poles.



You may enjoy my article: How to start bird watching.



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