can anyone reccomend some binoculars for sky observing,I dont understand the *x* power descriptions,thanx,Pete

Answer 1

For astronomical observing at night, it is more important to have a large "exit pupil" than high magnification. The exit pupil is the size of the bundle of rays coming out of the binoculars. At night, when your eye's pupil is dilated, it can admit a large bundle of rays. Some binoculars are made for night work, and have large exit pupils, while "regular" binoculars made for daytime have smaller exit pupils, in order to save size and weight.

A large exit pupil will make the image brighter than a small exit pupil, if it is night and your eye is dilated.

The power is the amount of magnification. If you look at a distant object, and then look at it with 7x binoculars, it will look 7 times bigger.

Generally 7 to 10 power is used for binoculars. At 10 power, it is hard to hold the binoculars steady enough so that the image doesn't shake around badly. There are plenty of astronomical objects that can be seen with 7 power.

In binocular descriptions, the first number is the power, and the second number is the diameter of the main lenses, in millimeters. In order to get a big exit pupil, you need a big lens for a given magnification, although a big lens does not guarantee a big exit pupil.

The best binoculars for astronomical use are probably 7x50 binoculars that are sold for this purpose. It is very useful to mount them on a tripod.

Answer 2

The first number before the x is magnification.

The second number refers to the aperture in mm.

e.g. 7x50 have seven times magnification with 50 mm aperture.

Aperture is important in resolving objects that are close together like double stars

Answer 3

the x power is nothing,
7x25 = the lens closest to your eye is 7 mm in diameter, the other # is the size of the front lens in this case 25 mm in diameter.
the larger the bigger # the more light is allowed the the optic device.
the distace from the front lens to the eye piece lens is the magnification

Answer 4

I used the ones i got for my daughter, from the early learning centre. They did the trick.