Astronomy Binoculars
Compared to telescopes, binoculars for astronomy are usually cheaper and more portable. Binoculars will allow you to see the moon in real detail, and view shadows as they move over lunar features.
Most people if asked would say that the best way to start exploring the night skys is with a telescope,
Binoculars can prove superior to a telescope for newcomers to this fascinating hobby. They have a wide field of view, which can make many night sky objects easy to find.
They also require no knowledge or expertise to set up, which can't be said for a telescope.
If you have a child that shows an interest in the night sky and the heavens, starting out with a pair of binoculars is ideal. If the sudden burst of interest wanes then your money wont have been wasted, as you can make use of them in lots of other ways. Again not possible with a telescope.
If buying a pair of astronomy binoculars, please be aware that as the objective lens (the big end!) will be quite large, you may need a tripod to hold the optics steady.
Even if you bought the best binoculars in the world, they would be of little use if you couldn't hold them steady.This is a critical point to consider with binoculars for astronomy. As the magnification increases, the shaking from the stress of trying to hold them steady increases too.
Its also easier and more natural for us to use two eyes to see rather than the one required for a telescope.
Apeture size is the critical specification for astronomy binoculars. Also called the objective lens, these are the lens on the the front, and need to be large to allow plenty of light in to enable good views. For astronomy, these lenses should be at least 40mm, preferably larger. You can discover the objective lens size by looking at the second number in the binoculars power. These are displayed as 10x50 or 8x40 etc. The first number is the magnification and the second is the aperture size. Try to get at least 8x magnification for astronomy. Any larger than 10x with apertures of 50mm will need a tripod.
Astronomy binoculars exit pupil also need to be matched to the pupil size of the viewer when their eyes have adjusted to the darkness. To find the exit pupil of a pair of binoculars divide the aperture size by the magnification. So all 10x50 binoculars have an exit pupil of 5mm, as do 8x40s. This is by no means an exact measurement but it can really help to concentrate all of the available light and make objects brighter for the observer. If the exit pupil of the binocular is larger than than the viewers pupil a lot of light can be lost and night sky objects can appear darker.
As we age our ability to adapt to changing light can decrease. For people under 30, with normal eyesight who are observing under a dark sky the pupils will dilate to about 7mm, this then starts to get smaller. In our 30s this drops to 6mm and for anyone over 40 the pupils probably wont open much over 5mm. As stated if the binoculars exit pupil is 7mm, and your pupil is only open to 5mm then quite a lot of the light is being lost and images will not be as bright.
Binoculars are a great investment for astronomy, helping you find much fainter objects by concentrating the available light.
