National Geographic 80-30124 Manual De Instrucciones página 7

Eyepiece:
An eyepiece is an optical accessory comprised of several lens elements. It determines the magnification of a
particular observing setup.
Huygenian Eyepiece
2 Lens Elements
Light
Barlow Lens:
A Barlow lens effectively increases the focal length of a telescope. It is inserted between the eyepiece and the
focuser/diagonal (depending on the optical setup) and multiplies the magnification power of the eyepiece.
For example, a 2x Barlow will double the magnification of a particular eyepiece.
Focal length (Telescope):
The focal length is the distance in millimeters between the objective lens or primary mirror and the point at which
entering light rays converge — otherwise known as the focal point. The focal lengths of the telescope tube and the
eyepiece are used to determine magnification.
Focal length (Eyepiece):
The focal length is the distance in millimeters between the center of the first lens element in an eyepiece and the
focal point. The focal lengths of the telescope tube and the eyepiece are used to determine magnification. Short
eyepiece focal lengths produce higher magnifications than long eyepiece focal lengths.
Kellner Eyepiece
3 Lens Elements
Eye Lens
Field Lens
Light
7 7
Plössl Eyepiece
4 Lens Elements
Eye Lens
Field Lens
Light
Barlow Le
2 Lens Elem
Light
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