While it is not terribly expensive to purchase an acceptable monocular or pair of binoculars, you should take several factors into consideration before selecting a brand and model, so as to avoid having to purchase more than one before finding a model suitable for your purposes.
First, you should decide whether a monocular or binoculars are preferable for you. Monoculars usually have a higher minimum price than binoculars, are more compact, and are easier to hold steady. Also, they don’t have the potential problem of having two non-aligned lenses, as some of the cheapest binoculars do. However, binoculars provide a wider range of vision, are available in more varieties, and may be less expensive. If you are looking for compact binoculars, keep in mind that some will fold up to take less space.
Almost all binoculars and monoculars have two specifications clearly marked on them or their packaging. These are indicated as “4×28”, “6×30” or a similar set of numbers. The first number (3x, 8x, etc.) is the magnification power, so the higher it is, the more magnification it will provide. Binoculars with higher magnification are usually more expensive. The amount of magnification necessary depends upon how you plan to use them. The 2nd specification indicates the lens size, and affects how large the binoculars are in general. However, your choice of a particular model shouldn’t be entirely based on these specifications, as quality and other characteristics also have a significant impact on performance. Binoculars are sometimes referred to as “opera glasses” or “field glasses.” Opera glasses usually have relatively low magnification.
Some binocular exteriors are made of metal, while others are made of plastic and/or rubber. Binoculars made of metal are more durable, although some are heavier than equivalent plastic binoculars. As with cameras, a metal exterior usually indicates a higher-quality pair of binoculars, because it wouldn’t be cost-effective to put poor-quality lenses in a metal body. On the other hand, plastic binoculars and monoculars can be of very good quality as well, but you cannot be as sure of it.
Two other features which may be included on a pair of binoculars are an adjustment wheel or night vision. Almost all binoculars have an adjustment control which changes the focusing. Some of the lowest-quality binoculars have an adjustment wheel which does little or nothing, however. Night vision binoculars are fairly expensive and sold by brands such as Yukon and ATN. Some models require a small battery.
Binoculars combined with other devices should also be considered, but are more expensive. Binoculars with built-in radios are useful for sporting events and more compact than carrying a separate radio and pair of binoculars. Binocular-cameras are also available, usually in digital format, for taking long range pictures as well as regular binocular usage. This type of camera is rarely available in 35mm format, but a 35mm film binocular-camera sold by National Geographic can sometimes be found on eBay. A drawback of binocular-cameras is that they are harder to hold steady than most regular cameras, unless they have a tripod and tripod mount. Another combination device is a binocular set with built-in compass, such as the Hammers 7×50 Marine binocular set. There is even a set of 8×28 binoculars made by Alpen which have a compass, thermometer, and clock built into them.
Waterproof binoculars are available as well, and are especially useful for marine applications or when it is raining. They have been sold by such brand names as Eddie Bauer, Simmons, and Sharper Image. These binoculars are usually relatively expensive. Waterproof monoculars have also been manufactured, but are much less common.
Many brand names sell binoculars, including some of the same brands which make cameras. Camera brands which also produce binoculars include Vivitar, Rokinon, Pentax, and Nikon. There are also a number of non-camera binocular brands, such as Tasco and Bushnell. Some of the more expensive binoculars are made by Steiner, Zeiss, and Leitz. Inexpensive binoculars are sold by Bell & Howell, Meikai, and some small Chinese-made brands like Lida. Monoculars are often made by the same brands as binoculars, but there are some brands which make monoculars and not binoculars, such as Radio Shack.
The accessories most likely to be included with a monocular or set of binoculars are a case and/or lens caps. While lens caps do provide protection for the binocular’s lenses, they can be easily lost, and have to be removed (and replaced) every time the binoculars are used. Lens caps which are attached to the binoculars may be preferable. A case or pouch is less likely to be lost and also provides protection for the binoculars.
When buying a used set of binoculars, be sure to check the lens to make sure there are no deep scratches or fungus, and see if the adjustment wheel turns freely. If possible, look through the binoculars before buying them, as problems with the lenses may not be apparent just from looking at them.
Many new and used binoculars/monoculars can be purchased on internet auction services and shopping websites. They are also available in department stores, some discount shops, and occasionally at yard sales or thrift stores. Keeping the above-mentioned considerations in mind, you should be able to find a binocular set or monocular which is affordable, of good quality, and capable of meeting your needs.