Transcript

INSTRUCTOR:

If you want to see more detail in fainter objects, then the next step is to collect more light. So in dark conditions, if you're lucky enough to be quite young, the pupil in your eye will delight to about 7 millimetres diameter. For someone my age, it'll probably open up just to about 5 millimetres or so diameter. That area, that aperture in your eye, is the amount of light that you can collect.

So, to do better than that, you can use a simple pair of binoculars with a larger lens to collect more light. So a typical pair of binoculars, 7 by 50 binoculars, will have a 50 millimetre objective lens. So that's 10 times the diameter of your pupil-- 5 millimetres to 50 millimetres. And of course, it's the area that's important for the light collection. So 10 times increase in diameter is 100 times increase in light collecting ability.

So immediately, with a pair of binoculars, you'll be able to see an incredible amount more detail, simply by collecting more light to see the fainter objects. Of course, there's a small amount of magnification involved as well. So you'll be able to see more detail that way. But the primary reason for using larger lenses and mirrors is to collect more light. The more light you've collected, the more you can do with your image.