The Eyepiece - Celestron The G-8 11023 Instruction Manual

Figure 4-1

The Eyepiece

The eyepiece, or ocular, is an optical element that magnifies the image
focused by the telescope. The eyepiece(s) fits into either the visual back
directly (see figure 4-1), the star diagonal, or an erect image diagonal. To
attach an eyepiece:
1. Loosen the set screw on the star diagonal so that it does not obstruct the
inner diameter of the eyepiece end of the diagonal.
2. Slide the chrome portion of the eyepiece into the star diagonal (see figure
4-2).
3. Tighten the set screw to hold the eyepiece in place.
To remove the eyepiece, loosen the set screw on the star diagonal and slide
the eyepiece out. You can then replace it with another ocular.
Eyepieces are commonly referred to by focal length and barrel diameter. The
focal length of each eyepiece is printed on the eyepiece barrel. The longer the
focal length (i.e., the larger the number) the lower the eyepiece magnification
(i.e., power) and the shorter the focal length (i.e., the smaller the number) the
higher the magnification. Generally, you will use low-to-moderate power when
viewing. For more information on how to determine power, see the section on
"Calculating Magnification."
Barrel diameter is the diameter of the barrel that slides into the star diagonal or
visual back. All Celestron C8 telescopes use eyepieces with a 1-1/4" barrel
diameter.
Figure 4-2
Telescope Basics • 21