Bushnell Telescope Terminology

	TELESCOPE TERMINOLOGY
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An optical instrument used for viewing distant objects, usually in the night sky.

Telescope Types

Refractor	Reflector	Naksutov-Cassegrain
An optical system utilising a series of glass lenses to refract or bend the light from a distant object such that it can be focused to a pont and magnified by an eyepiece. Popularised by Galileo in the 17th Century, it is sometimes referred to as a Galileo refractor.	The optical system in a reflector uses a primary mirror to reflect the light from a distant object such that it can be focused to a point and magnified by an eyepiece. Popularised by Sir Isaac Newton in the 17th Century it is sometimes referred to as a Newtonian reflector.	A design utilising a spherically curved front lens element in conjunction with a similarly curved primary mirror. This configuration provides incredibly sharp images in a compact folded-light path package. The total optical system provides a focal length much longer than the actual optical tube body length.

Objective Lens Size (or Aperture) The second number in the formula (100x114) is the diameter of the objective lens or mirror. The aperture relates directly to how bright images will appear and how much detail is revealed. The larger the objective lens the better. The size of the telescope's objective lens, or aperture, limits the amount of power that can be used effectively. As the magnification of an object increases, the brightness of the image decreases. This is because the light gathered by the telescope is being spread over a larger area. Aperture also limits the clarity of an image at increased magnification. When magnified beyond an aperture's recommended power, the image dims and becomes fuzzy.	Magnification (Power) Telescopes are often referred to by two numbers separated by an "x". For example: 100x114mm. The first number is the power or magnification of the telescope. With a 100x114 telescope, the object being viewed appears to be 100 times closer than you would see it with the unaided eye. The magnification of a telescope is determined by dividing its focal length by the focal length of the eyepiece in use. For example, a 500mm telescope with a 5mm eyepiece would magnify objects 100x. Thus a telescope can provide nearly any magnification required depending on the focal length of the eyepiece used. Since most objects in the sky are rather large, high magnification isn't necessary. Rather, a telescope that gathers a lot of light is needed to make dim objects appear brighter and sharper. The power or magnification contributes to the overall size and bulk of the telescope. This is because as the power increases, so must the physical size of the objective lens.
Erecting Lens Lens used with a refractor telescope when viewing land-based objects to correct the normally upside-down image provided by an astronomical telescope.	Penta Mirror Technology This patented Bushnell® technology breakthrough allows for left-to-right correct view of the stars (not backwards - as in most telescope models) taking the guesswork out of where to move the telescope. This feature provides unparalleled ease of use for finding and tracking objects with a 90 degree viewing angle and 1.25" / 31.7mm eyepiece adaptor.
Finderscope On most astronomical telescopes a lower powered finderscope with a wider field-of-view lets the user quickly locate the object to be viewed by the high magnification main telescope. There are 2 types of finderscope, optical and red dot.	Resolution Resolution, or definition is the ability of a binocular to distinguish fine detail and retain clarity.
Focal Length The measured light path of the optical system (tube length) typically measured in millimetres.	Rotary Power Turret This patented Bushnell feature allows for magnification and accessory changes to occur through a simple twist of the turret or accessory dial. Accessories are incorporated into the telescope so there are no loose parts. Magnification and accessory changes can be made instantaneously to suit viewing conditions.
Barlow Lens An auxilliary lens that increases the power by a factor. For example, a 2x Barlow doubles the telescope magnification.	Focusing Knob Controls the rack and pinion focusing system. Permits smooth movement of eyepiece for precise, sharp images.

How to choose

When selecting a telescope, consider which target objects you plan to explore as well as you level of experience. For viewing most night sky objects, you'll want a telescope with as much aperture as possible. Keep in mind that as the size of the objective lens or mirror increases, so does the size of the telescope. So be sure to select a telescope that is not too heavy to manage or too complicated for you to set up - especially if portability is an issue.

Refractors Refractors are less affected by atmospheric instabilities, making them perfect for observing the moon and planets. Perfect for first time and novice astronomers, small refractors are lightweight, portable and require very little maintenance. If you are interested in viewing both land and celestial objects, refractors are equipped for both uses.	Reflectors Reflectors feature larger apertures for a wide range of viewing at an affordable price. Designed with the eyepiece located at the top of the tube, reflectors are more comfortable to use for viewing night sky objects such as nebulae, the moon, planets and galaxies. Reflectors tend to be heavier and larger than refractors.
Eyepieces Lower power eyepieces provide a wider field-of-view and a brighter image making them ideal for viewing the full moon, planets, star clusters, nebulae and constellations. To focus in on the finer details of the moon and planets such as mountains, ridges and craters, use an eyepiece with higher magnification.	Mounts There are two basic types of telescope mounts, the altitude-azimuth (or altaz) and the equatorial. Altaz mounts are the easiest to manoeuvre and are ideal for first-time astronomers. Equipped with a manual control or motor drive that allows you to follow the movement of objects across the night sky, equatorial mounts are ideal for more experienced astronomers.

Types of Telescope Mounts

Easy Track® Mount
An altaz mount that allows quicker and easier set-up and storage and reduces image shake caused by wind or ground tremors.
Equatorial Mount
An advanced telescope mount that compensates for the earth's rotation.
Kinematic Mount
Undoubtedly the most precise, yet simple telescope mount in years, this high precision altaz mount uses the principle that it requires three points to form a plane. Designed for optimum shape, the Kinematic mount features three points of contact in both horizontal and vertical planes.

The mount secures the telescope to the tripod. It allows you to move your telescope horizontally and vertically. There are two primary types of telescope mounts, altitude-azimuth (or altaz) and equatorial.

Altaz mounts move up-down and left-right. Equatorial mounts are tilted to align with the rotational (polar) axis of the earth.

Yoke Mount
A U-shaped Altaz mount
Tripod
A tripod serves as a steady platform for the telescope to allow hands free use. Because of its powerful magnification, even the slightest jiggle of the telescope is enough to move it from its target. tripods feature 3 adjustable legs so the telescope can be used even when the ground is uneven.