Backyard Voyager

Choosing a telescope from among the multitude of (slightly) different optical types

Celestron 2" Eyepiece and Filter Kit

All of the components beginners needs, including a 2" diagonal and 2" barlow lens, to upgrade their new SCTs from the standard 1.25" diagonal and eyepieces to a widefield format.

BackspacerThe Magnification MythspacerNext

Probably the most common myth about telescopes is that high levels of magnification or "power" are required to see distant objects. This is entirely untrue. In the first place, a telescope's function is not to magnify, but to gather light through a mirror or refracting lens. The diameter of the mirror or lens, its aperture, determines how much light it will gather. The amount of magnification a telescope is able to give depends on the scope's aperture, its focal length and the focal length of the eyepiece used.

M42

Star fields, open clusters

and large diffuse nebula

are betterviewed with low

magnification.

A telescope's size (its aperture in milimeters or inches) isimportant, because the more light the telescope can gather, the easier it is to resolve detail at higher levels of magnification. Strictly speaking, the companies selling "DSTs" are telling the truth when they say that a telescope can deliver 500x-- any telescope can. But, whether or not you will be able to actually see anything at that level is an entirely different story. Most amateur astronomers seldom use more than 200X.

Some targets require more amounts of magnification, while

Jupiter

Planets, the lunar surface

and some galaxies require

higher magnificatrion.

others are ideally viewed with less. For this reason amateur astronomers will eventually build a collection of diferent sized eyepieces. To view large nebulae or open star clusters such as the Pleiades requires low levels of magnification, usually acquired by using 2" eyepieces that give a wider field of view (FOV). To increase magnification, simply switch eyepieces. Generally speaking, high magnification is usually achieved by using 1.25" eyepiece with a short focal length. A 5mm eyepiece, for example, will magnify 100% more than a 10mm eyepiece of the same type.

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