Celestron C8-S User Manual
Page 11
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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.”
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The AST telescopes come with a 6x30 finderscope used to help you locate and center objects in the main
field of your telescope. To accomplish this, the finder has a built-in cross-hair reticle that shows the optical
center of the finderscope.
Start by removing the finder and hardware from the plastic wrapper. Included are the following:
Eyepiece
Star Diagonal
Visual Back
Figure 2-10