Straight Spotting Scope
A spotting scope is a hand-portable telescope fitted with a large objective lens that is used for terrestrial observation. Although not as power as a dedicated astronomical telescope, the spotting scope has a significant advantage on that they are less specialized, easier to carry, and often more robust than standard telescopes. Normally used in conjunction with a tripod, spotting scopes are commonly fitted with a range of eyepieces to achieve differing powers of magnification and image clarity. Some also act as lens attachments for SLR cameras, and can be used for ‘digiscoping,’ using the extra zoom afforded by the scope to take very detailed long-distance images.
Spotting scopes normally come in one of two configurations – straight or angled, dependant on the location of the eyepiece. Each type has specific uses, depending on the circumstances and activity in which they are used. For this article, we are going to focus on straight spotting scopes, which use a similar lens arrangement to Galileo’s famous refractor telescope – the large objective lens at the front bends the light onto a focal point, where a second lens or prism bends the light again into an image that is capable of being processed by the human eye. Straight spotting scopes are ideal for use free-hand, and can be much easier to track movement with than angled spotting scopes. They are ideal for hunting, birdwatching, and use on safari.
Straight spotting scopes make great telescopes for use in the field. Their rugged, durable construction (many are manufactured with a durable rubber outer casing for additional protection) and eminent portability make them an ideal choice for many types of outdoor activity. They can be used from a long-term static location such as a hide or a laying-up point, or used while on the move, giving them an incredible versatility.
A typical straight spotting scope is normally around 300-400mm long, with a lens of at least 60mm in diameter. Most lenses are between 60-80mm, though both larger and smaller lenses exist for certain specialized activities. A larger lens makes for a better, clearer image, while smaller lenses make the scope much less bulky and easier to carry and relocate.
It is also possible to pick up spotting scopes with variable zoom lenses, but it is important to bear in mind that at higher magnifications zoom lenses can often result in a shortened field of vision, as well as limiting the light that can be captured by the scope and thus affecting the clarity of your final image.