Coated Optics
Coatings on lens surfaces reduce light loss and glare
due to reflection, resulting in a brighter, higher-contrast
image with reduced eyestrain. Bushnell® spotting
scopes are coated with a microscopic film of magnesium
fluoride. More coating leads to better light transmission.
Types of Coating
Coated – A single layer on at least one lens
surface.
Fully Coated – A single layer on all air-to-glass
surfaces.
Multi-Coated – Multiple layers on at least
one lens surface.
Fully Multi-Coated – Multiple layers on all
air-to-glass surfaces.
Exit Pupil
The exit pupil refers to the size of the column of
light that exits a spotting scope. The larger the
exit pupil, the brighter the image. To determine
the size, divide the objective lens diameter by
the power. Thus, a 15x45 model has an exit pupil,
or useable light, of 3mm (45/15 = 3mm).
Eye Relief
The distance a spotting scope can be held away from
the eye and still present the full field-of-view.
Extended or long eye relief reduces eyestrain and
is ideal for eyeglass wearers.
Field-of-View (F.O.V.)
Field-of-view is the side-to-side measurement of
the circular viewing field or subject area. It
is defined by the width in feet or meters of the
area visible at 1000 yards or meters. A wide field-of-view
is better for following fast-moving action or
scanning for wildlife. Generally, the higher the
magnification, the narrower the field-of-view.
 Folded Light Path
A combination optical configuration using lenses
and mirrors to create a total scope length much
shorter than the total focal length of the system.
This provides a compact design yielding long focal
length performance.
Magnification (Power)
Spotting scopes are often referred to by numbers
separated by an "x". For example:
15–45x60.
The first number is the power or magnification
of the spotting scope. With a 15–45x60 variable
power spotting scope, the object being viewed appears
to be 15–45 times closer than you would see
it with the unaided eye.
Near or Close Focus
The closest you can be to an object and maintain
visual clarity.
Multi-Position Eyepiece
Bushnell's exclusive multi-position eyepiece
is available
on our 78-7350 and 78-7360 Spacemaster® models.
This revolutionary eyepiece features an infinite
number of viewing positions between straight-thru
and 90 degrees – providing flexibility for
viewing comfortably in any situation.
Objective Lens Size
The number after the "x" in the
formula: (15–45x60) is the diameter of the
objective or front lens. The larger the objective
lens, the more light that enters the spotting scope
and the brighter the image.
Prism Glass
Most optical prisms are made from borosilicate (BK-7)
glass or barium crown (BaK-4) glass. BaK-4 is the
higher quality glass yielding brighter images and
high edge-to-edge sharpness.
Prism Systems
The prism system turns what would otherwise be an
upside-down image right-side-up.
 Roof Prism System
The prisms overlap closely, allowing the objective
lenses to line up directly with the eyepiece. The
result is a slim, streamlined shape in which the
lenses and prisms that magnify and correct
the image are in a straight line.
 Porro Prism System
The objective or front lens
is offset from the eyepiece.
Porro prisms provide greater depth
perception and generally offer a wider field-of-view.
 Rainguard®
Our exclusive, patented, hydrophobic (water-repellent)
coating on which condensation from rain, fog or
snow forms in much smaller droplets than on standard
coatings. Smaller droplets scatter less light which
results in increased light transmission and a clearer
image.
Resolution
Resolution, or definition, is the ability of a spotting
scope to distinguish fine detail and retain clarity.
Waterproof/Fogproof
Some scopes are sealed with O-rings and nitrogen-purged
for waterproof and fogproof protection. These models
are able to withstand complete immersion and remain
dry inside. |
