The Eyepiece

The eyepiece, or ocular, is the 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 the eyepiece:

1.Loosen the thumbscrew on the star diagonal so 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.

3.Tighten the thumbscrew to hold the eyepiece in place.

To remove the eyepiece, loosen the thumbscrew on the star diagonal and slide the eyepiece out.

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 or magnification; 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. The NexStar uses eyepieces with a standard 1-1/4" barrel diameter.

The Star Pointer Finderscope

The Star Pointer is the quickest and easiest way to point your telescope exactly at a desired object in the sky. It's like having a laser pointer that you can shine directly onto the night sky. The Star Pointer is a zero magnification pointing tool that uses a coated glass window to superimpose the image of a small red dot onto the night sky. While keeping both eyes open when looking through the Star Pointer, simply move your telescope until the red dot, seen through the Star Pointer, merges with the object as seen with your unaided eye. The red dot is produced by a light-emitting diode (LED); it is not a laser beam and will not damage the glass window or your eye. The Star Pointer comes equipped with a variable brightness control, two axes alignment control and two quick-release dovetail mounting brackets (one for the NexStar telescope and one for mounting the Star Pointer on other sized telescopes). Before the Star Pointer is ready to be used, it must be attached to the telescope tube and properly aligned:

ON/OFF

Variable Brightness

Control

Glass Window

Azimuth Control

Knob

Mounting Track

Altitude Control

Knob

Dovetail Mounting Bracket

Figure 1-5: The Star Pointer Finderscope with Mounting Bracket

Star Pointer Installation

1.First, remove the two 8-32 x ¼" screws located on the top portion of the telescope's rear cell.

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Celestron NexStar 8i manual Eyepiece, Star Pointer Finderscope, Star Pointer Installation