Field Scopes For Bird Watching
The use of field scopes for bird watching is one of the things that makes the amateur into a full fledged birder. What are field scopes and how are they used for bird watching?
Field Scopes For Bird Watching
The term field scope refers to a telescope that is designed for use in outdoor activities such as bird watching. They are available in a wide variety of sizes and magnifications. Although binoculars are often used for casual bird watching, it is the field scope that makes observation of rare species possible. The field scopes used for bird watching are a bit expensive. They range from $400 to over $2000.
There are several terms that you should know when selecting an evaluating a field scope. The objective lens is the basic object that captures and projects the image to the eyepiece. The objective lens transmits an image that is upside down and backwards. The eyepiece is the lens that you actually look through and that provides the magnification. Many field scopes used for bird watching have replaceable eyepieces to allow different magnification levels.
Erecting prisms are what turn the image right side up and flip it from left to right so that the image seen through the eyepiece appears natural. The aperture is the diameter of the front lens. It is usually expressed in mm and is the first term given in the description of the field scope.
Eye relief refers to how far your eye can be from the eyepiece and still receive a good image. This factor is important to people who wear glasses and can not press their eye directly against the eyepiece. Chromatic aberration is what happens when light passes through a glass lens. The lens tends to bend the light as is seen in a prism. Most scopes are able to focus one color, but this leaves the surrounding colors slightly out of focus. Field scopes that use mirrors in place of glass lens have little or no chromatic aberration, but are much more expensive.
When you understand the terminology used in describing scopes, you can evaluate them based on their quality versus your personal budget. Field scopes are either straight or angled. The angled scopes have a 45 degree angle between the main body and the eyepiece and most birders prefer them. Experienced birders also recommend optical excellence and usability as the two factors to consider. Usability would include lighter weight and ease of use in the field.