After you look at the lens and magnification numbers of Celestron binoculars, you will want to look at the exit pupil. This number represents the brightness of an object in the binoculars when it is viewed in a situation where there is little light. The higher the exit pupil number is, the brighter the object will appear. It is hard to understand exit pupil of Celestron binoculars until you have tried out a few different pairs for comparison. Here is how to do it:

Aim your binoculars towards a light source. Then, while keeping the binoculars about 12 inches in front of your face, look through the eye pieces. You should be able to notice a bright speck of light in the eye pieces. This is the exit pupil, a tunnel which allows light to flow through the binoculars barrels and get to your eyes. The bigger the speck of light you see, the larger the exit pupil is. When exit pupil is measured for Celestron binoculars, it is done by taking the diameter of the lenses and dividing it by the magnification. When you buy Celestron binoculars, you won’t always see the exit pupil listed but you can figure it out for yourself. For example, in a pair of Celestron binoculars with a lens of 40 and a magnification of 8, then the exit pupil is 5. It is important to get a high exit pupil if you think you will be using your binoculars when there isn’t a lot of light, such as bird watching at dusk.