Meade DS-90 Instruction Manual download pdf (Page 2)

Refracting Telescopes use a large objective lens as their primary

light-collecting element. Meade refractors, in all models and apertures,

include achromatic (2-element) objective lenses in order to reduce or

virtually eliminate the false color (chromatic aberration) that results in

the telescopic image when light passes through a lens.

Reflecting Telescopes use a concave primary mirror to collect light

and form an image. In the Newtonian type of reflector, light is reflected

by a small, flat secondary mirror to the side of the main tube for

observation of the image.

In the refracting telescope, light is collected by a 2-element objective

lens and brought to a focus at F.

In contrast, the reflecting telescope uses a concave mirror for this

purpose.

Eyepiece

2-Element

Objective Lens

Eyepiece

Concave

Mirror

Secondary

Mirror

Refracting Telescope

Reflecting Telescope

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Meade DS-90 Instruction Manual Page 2