Celestron CGEM 1100 User Manual
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The visual back is the accessory that allows you to attach all visual accessories to the telescope. The telescope optical tubes
come with the visual back installed. If it is not already on the tube it can be attached as follows:
1.
Remove the rubber cover on the rear cell.
2.
Place the knurled slip ring on the visual back over the threads on the rear cell (Fig 2-8).
3.
Hold the visual back with the set screw in a convenient position and rotate the knurled slip ring clockwise until tight.
Once this is done, you are ready to attach other accessories, such as eyepieces, diagonal prisms, etc.
If you want to remove the visual back, rotate the slip ring counterclockwise until it is free of the rear cell.
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The star diagonal is a prism that diverts the light at a right angle to the light path of the telescope. This allows you to observe
in positions that are physically more comfortable than if you looked
straight through. To attach the star diagonal onto the optical tube:
1.
Turn the set screw on the visual back until its tip no longer extends into
(i.e., obstructs) the inner diameter of the visual back.
2.
Slide the chrome portion of the star diagonal into the visual back.
3.
Tighten the set screw on the visual back to hold the star diagonal in place.
If you wish to change the orientation of the star diagonal, loosen the set
screw on the visual back until the star diagonal rotates freely. Rotate the
diagonal to the desired position and tighten the set screw.
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The eyepiece, or ocular, is an optical element that magnifies the image focused by the telescope. The eyepiece fits into either
the visual back directly or the star diagonal. To install an eyepiece:
1.
Loosen the set screw on the star diagonal until the tip no longer extends into the inner diameter of the eyepiece end of
the diagonal.
2.
Slide the chrome portion of the eyepiece into the star diagonal.
3.
Tighten the set screw on the star diagonal 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 replace it with another
eyepiece (purchased separately).
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 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.”
Eyepiece
Star Diagonal
Visual Back
Figure 2-8