Spotting Scope Terminology:
Straight Straight eyepiece design
The straight eyepiece position works well when viewing downward from an elevated platform, such as a deck, patio, hillside, anytime you’re above the subject be viewed. Many novice users also favor the more natural line of sight afforded by the straight eyepiece – especially when trying to follow wildlife on the move.
Angled eyepiece design
If you tend to share your scope with others, you’ll find the angled eyepiece position of the Nomad spotting scope readily accommodates folks of many different heights with less adjusting of the tripod. The angled eyepiece position also works well for watching birds high in the treetops, scanning higher elevations for wildlife, or gazing up at the moon.
What do the Numbers mean
What the numbers mean. Spotting Scopes are normally identified by two numbers. The first numbers are the magnification (20-60X) for a variable power scope and the second number is the diameter of the objective lens in millimeters (mm). For example, 20-60X60 means the Spotting Scope magnifies objects 20-60 times and the objective lens is 60 mm in diameter.
What is Eye Relief?
Eye Relief is the distance, expressed in millimeters, from the ocular (eyepiece) lens to the point where the eye is positioned to view the entire image. Eye relief is affected by magnification, the number of lens elements, and field of view. Spotting Scopes designed with long eye relief are usually preferred by those who wear eyeglasses. Most Spotting Scopes provide 8-13 mm of eye relief. Spotting Scopes with “long eye relief” provide from 14-20 mm (or more) eye relief.
What is Field of View (FOV)
Field of View describes the size of the area that can be seen through the Spotting Scope and expressed as the number of feet per 1000 yards of distance, the higher the magnification the narrower the field of view. A wider field of view is often preferred by hunters who want to scan large areas for game or for viewing sporting events.
What does Resolution mean?
Resolution describes how sharp or clear an object appears when viewed. Resolution is primarily determined by the objective lens diameter. The larger the diameter of the objective lens, the better the resolution. However, lens coatings, lens alignment, quality of glass, and quality of prisms also affect how sharp a viewed image will be.
What are Prisms?
Porros prisms are used in Spotting Scope. The Porro prisms used in spotting scopes are larger than used in binoculars and have different quality glass used in the prisms.
What are Optic Coatings?
Optics are coated to prevent glass surfaces from reflecting light and losing it. The very best optics are “Fully Multi-Coated” which means multiple coatings are layered fully onto all glass surfaces. “Fully coated” means all “air to glass” surfaces have been coated with at least one layer of coating. “Coated” means some surfaces have been coated.
What does Exit Eye Pupil Describe?
A measurement of how much light is usable by a spotting scope. Generally, the larger the exit pupil, the brighter the image will appear, particularly in dim light. Exit pupil is determined by dividing the diameter of the objective lens by the magnification. For example, a 20-60x60mm Spotting Scope has an exit pupil of 3-1 mm. For general use in bright light, an exit pupil of 2.5 mm is sufficient and 4 mm and higher generally allow better viewing in dim light. Lens coatings and the human eye also affect how well a binocular performs in dim light.
Objective Lens Diameter
Objective Lens Diameter is important because many of the performance characteristics of a Spotting Scope are determined by the diameter of this lens. The function of the objective lens is to collect light and direct it to the prisms or eye pieces. The larger the diameter, the more light will reach your eye thus providing a brighter and sharper image. However, the larger the diameter, the heavier and bulkier the Spotting Scope will be. You will find there are many different combinations of magnification and objective lens diameters to meet specific applications.
