slparker wrote:Wouldn't you just call it a telescope?
Telescopes and binoculars have a different optical design. Binoculars and telescopes both have objective lenses (of long focal length) and eyepieces (of short focal length), but binoculars also have the light path intersected by a pair of prisms (these can be (conventional) porro prisms - so the light path is a z shape, or roof prisms (which give a straight light path). The purpose of the prisms is to make the design much more compact (given the long focal length of the objective lens) as the light path is sort of folded up, and it also inverts and laterally reverses the image - so the image is both upright and the right way round. This is important for many uses - e.g. horse racing - so you can read the number of the horse, or bird watching - so if the bird flies out of view, you can move the instrument in the right direction. Telescopes used for terrestrial viewing can achieve the same thing using prisms, mirrors or extra lenses (some telescopes use a lens to invert the image, but it is till flipped horizontally). Astronomical telescopes don't bother with this.
Binoculars, having two separate instruments also, have a major advantage in that you see a 3D or stereo view. This is important in bird watching and other fields such as surveillance. The 3D effect is increased by having the objective lenses spaced at a larger distance apart than your eyes. So binoculars with roof prism do not have a very big 3D effect, nor do some designs with porro prisms where the objective lenses are placed close together (but those designs are more compact). Some military binoculars - e.g. those in forts or on ships often use binoculars with the objective lenses at large distances apart - a metre or so, to greatly increase the 3D effect. This is useful in judging the relative distances of say of a flotilla of ships.
Some people are colour blind, and similarly, some people are stereo blind, even if both eyes function normally. I guess these people would buy monoculars?