Celestron CR-150 HD - Manual (Page 21)

Telescope Basics • 21
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
accessory adapter. Your CR-150 HD refracting telescope can use eyepieces with
both a 1-1/4" barrel diameter and 2" barrel diameter. To use a 2" barrel eyepiece,
the 1 1/4" accessory adapter must first be removed. To do this, simply loosen the
two chrome thumbscrews located around the focuser barrel (see figure 4-1) and
remove the 1 1/4" adapter. Once removed, a 2" eyepiece or accessory can be
inserted directly into the focuser barrel and secured with the two thumb screws.
Figure 4-1 Figure 4-1 Figure 4-1 Figure 4-1 Figure 4-1
Focuser Knob
1 1/4" Accessory
Adapter
2" Focuser
Barrel
Built-in T-Adapter
Thread
Focuser Tension
Screw