Celestron C100ED-R, C80ED-R manual Balancing the Tube in R.A, Installing the Eyepieces, Figure

Installing the Eyepieces

The eyepiece, or ocular as it is also called, is an optical element that magnifies the image focused by the telescope. Without the eyepiece it would be impossible to use the telescope visually. The eyepiece fits directly into the focuser. To attach an ocular:

1.Loosen the set screw on the eyepiece adapter so that it does not obstruct the inner diameter of the barrel.

2.Slide the chrome portion of the eyepiece into the focuser.

3.Tighten the set screw to hold the eyepiece in place.

To remove the eyepiece, loosen the set screw on the focuser and slide the eyepiece out. You can replace it with another ocular.

Focuser Tension

Screw

1 ¼" Eyepiece

Adapter

		T-Adapter
		Thread
	2" Focuser
Focuser Knob
	Barrel

Figure 2-11

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.”

Your 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" eyepiece adapter must first be removed. To do this, simply loosen the two chrome thumbscrews located around the focuser barrel (see figure 2-11) 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.

Balancing the Tube in R.A.

To eliminate undue stress on the mount, the telescope should be properly balanced around the polar axis. In addition, proper balancing is crucial for accurate tracking if using an optional motor drive. To balance the mount:

1.Release the R.A. Clamp (see figure 2-15) and position the telescope off to one side of the mount (make sure that the mounting bracket screw is tight). The counterweight bar will extend horizontally on the opposite side of the mount (see figure 2-12).

2.Release the telescope — GRADUALLY — to see which way the telescope “rolls.”

3.Loosen the set screw on the counterweight.

4.Move the counterweight to a point where it balances the telescope (i.e., it remains stationary when the R.A. clamp is released).

5.Tighten the set screw to hold the counterweight(s) in place.

These are general balance instructions and will reduce undue stress on the mount. When taking astrophotographs, this balance process should be done for the specific area at which the telescope is pointing.

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