Binoculars & Monoculars
Binoculars, monoculars, and spotting scopes are portable devices for magnifying objects at a distance, making them easier to see. The ability to see and observe prospective targets, shelter, prey, etc... from a distance before you can be seen is a significant advantage over those without the ability.
Binoculars offer the advantage of stereo vision when compared to monoculars and spotting scopes, preserving some depth perception and avoiding the necessity to close one eye.
Monoculars offer the same magnification as binoculars at slightly less than half the weight, volume, and complexity. They are generally considered to be more durable due to their greater simplicity. For the purposes of light-weight bug out gear these advantages are significant.
All quality telescopes (single or dual) have a few main components, the quality of these components have the greatest effect on the overall quality of the device.
- Eyepiece - The eyepiece is the lens through which the magnified image is viewed, a reasonable relief should be present to make the device comfortable to use.
- Objective Lens - The objective lens is the large, forward lens through which all light enters the device. The larger this lens is, the brighter and clearer the image you perceive will be. The size, in millimeters, of the objective lens is stated in the second part of the expression of the dimensions of a optical device(i.e. 8x32).
- Prisms - Prisms are the most important part of a pair of binoculars for magnification. The material from which they are made and the type of prism they are will determine the quality of the image they produce and the form factor that the device will take. The two most popular materials are BaK4 and BK-7, BaK4 is generally considered to the optically superior material; however, both of these materials are found in high-quality devices. The two prism shapes are Porro and Roof, the shape of the prism affects both the performance and form factor. Porro prisms generally provide better performance, but roof prisms offer a more compact device. The issue of prism shape and material are hotly debated among optics aficionados.
Binoculars and their kin will come with various features
- Coating - Coatings affect the efficiency of the transmission of light through both prisms and lenses. There are three classifications of coating; coated(could be a coating on a single lens or more), multi-coated(2 or more coatings on one lens or more), and fully multi-coated (one or more coatings on all glass surfaces) with fully multi-coated being ideal. Coatings cause lenses to appear to colored (typically red, green, or blue), however, the coatings are themselves absolutely clear.
- Fog-Proofing - Fog-Proofing is a very helpful feature to have, it prevent the internal glass surfaces from fogging over due to temperature and moisture changes. This is typically accomplished by nitrogen purging, or filling a sealed device with dry nitrogen so there is no moisture to condense on the optics surfaces.
- Magnification - Magnification, or power, is typically expressed in multiples(2x,4x,8x, etc...) of the size of the actual image. The greater the magnification, the larger the image and the darker and less clear the image will be depending upon the size of the objective lens. Some scopes and binoculars are available with a zoom feature giving them variable magnifications, this adds to their complexity and can potentially decrease the quality of the image as magnification is increased, but is a very convenient feature to have.
- Range-Finding - Optical devices often have range finding capabilities, electronic or optical, that allow you to determine how far away a given object is. Electronic range finders use lasers to measure a distance. Optical range finders typically use markings that are visible through the device that are spaced at fixed minutes-of-angle(MOA being approx. 1 inch at one yard) and require the user to perform some math to determine the distance.
- Shock-Proofing - Shock-proofing is more a measure of the quality of build and the amount of shock absorbent materials (such as rubber)used to manufacture the device. Shock-proofing a device allows it to suffer a more violent impact than non shock-proofed devices.
- Water-Proofing - Water-proofing seals a device against entry of water, which is potentially devastating to an optical device.
Most optical devices, particularly those with higher magnification, have the ability to be mounted for better stability. For items such as spotting scopes this is essential.
- Monopods - Some walking sticks have adapters on the top where an optical device or camera can be mounted for stability. It is not the most secure brace but is better than holding a device by hand alone.
- Bipods - Bipods, such as shooting sticks, can brace an optical device such as a scope but this is typically an improvization.
- Tripods - Tripods come in various sizes but offer the greatest stability of man-portable devices. Small tripods are easily stowed in a cargo pocket or rucksack.
- Clamps - Window mounts can clamp an optical device, night vision device or camera in a secure position for observation.