For most people, the predominant piece of equipment associated with astronomy is the telescope. However, binoculars can be a very useful piece of equipment for the astronomer, especially for amateurs.
They provide good wide field images at low magnification which can allow novice astronomers to find their way around the night sky much more easily than with higher magnification telescopes. Binoculars are, by definition, two oculars (two eyepieces).
A binocular is simply two refracting telescopes packaged together so that both eyes can be used to look at distant objects at the same time. They incorporate a number of prisms for three purposes: Firstly, to reduce the length of the tubes in order to make them more compact and therefore, more portable. Secondly, the prisms are used to put the image upright again (because binoculars are not usually used for viewing the cosmos). Lastly, the prisms make it possible to reduce the width between the eyepieces so that viewing is possible with both eyes.
There are also some disadvantages with using binoculars for astronomy. Most importantly, they do not normally include telescope mounts, although some of the larger sizes can be fitted with photo tripod adapters. Without telescope mounts of some kind, large binoculars are heavy and difficult to hold up to your eyes for sustained long periods. Also, as a rule, binoculars do not allow eyepiece interchange.
For more advice and a look at a comprehensive range of binoculars, visit Sherwoods Photographic, a family owned company who specialise in telescopes and binoculars.