Bushnell Telescope Terminology Instruction Manual

TELESCOPE TERMINOLOGY

Achromatic –

This is an almost nonexistent color that is placed on a lens to give the image
a sharper, crisper look.

Aperture - The measured diameter of the objective lens.
Astronomical - Astronomical telescopes are designed specifically for

observing heavenly bodies: stars, planets, moons, comets, etc. They are
fitted with special features to stabilize the telescope and track the movement
of stars and planets across the sky. They are very high powered, with
magnifications of 40x to 600x depending on the model of the telescope used.

Barlow Lens – This lens is used between the focusing tube and the
eyepiece. A 2X Barlow lens doubles the telescopes magnification.

Exit Pupil – Shaft of light emitted from the oculars. This is expressed in
millimeters: determined by dividing the size of the objective lens by the
power.

Eye Relief – Distance behind the binocular eyepiece at which the entire field
of view is visible.
Field Of View – Widest Dimension of the Diameter of the field being
viewed, expressed in number of feet at 1000 yards.

Focal Length - The distance between the Objective Lens and the eyepiece
measured in millimeters.

Objective Lens - The Objective lens is the lens closest to the object being
viewed. Ultra-sharp, coated for superior light gathering properties.
Aberration free. Your Bushnell telescope features a technologically superior
achromatic objective lens that provides bright, clear, and sharp images.

Oculars – Are the eyepiece lenses.
Optical Formulas - Telescopes are described by a numerical representation

such as 450x60mm. The first number is the maximum magnification (an
object will appear 450 times closer than viewed with the naked eye) and the
second number is the diameter of the objective lens (the closest to the
viewed object).

Power – The power equals magnification.
Zenith – The point on the celestial sphere that is directly over the top.