Using and choosing binoculars for astronomy

Holding binoculars steady

The steadier you can hold binoculars, the more you will see. Resting them on something seems like a good idea but is difficult when the object you are viewing is high up. In the same way, although most binoculars can be mounted on tripods, the standard photographic tripod gets in your way when you’re trying to observe objects nearly overhead.

Image-stabilised binoculars are costly but they can outperform other binoculars in their size class, when hand-held, as the stabilisation makes it possible to see much finer detail and fainter stars that you might otherwise miss as you try to view a jiggling image.

25x105 binoculars on tripod
Using 25×105 binoculars on a purpose-built tripod. The binoculars have a 45º prism to avoid a cricked neck when viewing overhead, and the mounting has a counterweighted pivot to keep them clear of the tripod. But ordinary photographic tripods are not so convenient

Testing binoculars

If you get the chance to test a range of binoculars before you buy, a good test is to view a small object against a bright sky, such as a chimney pot or TV aerial. Look carefully for signs of false colour around the edges of the object. The more expensive models tend to have barely noticeable false colour, wider fields of view and very little image distortion. Check for flatness of field by looking at a wall where everything is the same distance from you. The view should be sharp from edge to edge.

The cheaper binoculars are more likely to have a less rugged construction. The prisms that reduce the length of the light path and bring the image the right way up can become misaligned through rough treatment, giving overlapping images that can be uncomfortable to view, and it usually costs more than the binoculars are worth to get them repaired, even if it is possible. However, for astronomy you needn’t buy the rugged binoculars that are recommended for field use, such as for bird spotting, which are often waterproof. Few astronomers observe in the rain!