8
TELESCOPE TERMS TO KNOW:
Diagonal:
A mirror that deflects the ray of light
90 degrees.
With a horizontal telescope tube, this device
deflects the light upwards so
that you can comfortably observe by looking
downwards into the eyepiece.
The image in a diagonal mirror appears upright,
but rotated around its
vertical axis (mirror image).
Focal length:
Everything that magnifies an
object via an optic lens has a certain focal
length. The focal length is the length of the path
the light travels from the surface of the lens to
its focal point. The focal point is also referred
to as the focus. In focus, the image is clear. In
the case of a telescope, the focal length of the
telescope tube and the eyepieces are used to
determine magnification.
Lens:
The lens turns the light that falls on it
around in such a way so that the light gives
a clear image in the focal point after it has
traveled a certain distance (focal length).
Eyepiece:
An eyepiece is a system made
for your eye and comprised of one or more
lenses. In an eyepiece, the clear image that is
f=20 mm
f=12.5 mm
The Moon
f=20 mm
f=12.5 mm
Terrestrial Images
