Celestron CR-150 HD - Manual (Page 22)

22 • Telescope Basics
To focus your telescope, simply turn either of the focus knobs located under the focus
tube (see figure 4-1). Turn the focus knobs until the image is sharp. Once sharp, turn the
knobs toward you to focus on an object that is closer than the one you are currently
observing. Turn the knobs away from you to focus on a more distant object than the one
you are currently observing.
When working with any optical instrument, there are a few things to remember to ensure
you get the best possible image.
• Never look through window glass. Glass found in household windows is optically
imperfect, and as a result, may vary in thickness from one part of a window to the next.
This inconsistency can and will affect the ability to focus your telescope. In most cases
you will not be able to achieve a truly sharp image, while in some cases, you may actually
see a double image.
• Never look across or over objects that are producing heat waves. This includes asphalt
parking lots on hot summer days or building rooftops.
• Hazy skies, fog, and mist can also make it difficult to focus when viewing terrestrially. The
amount of detail seen under these conditions is greatly reduced. Also, when photograph-
ing under these conditions, the processed film may come out a little grainier than normal
with lower contrast and underexposed.
• If you wear corrective lenses (specifically glasses), you may want to remove them when
observing with an eyepiece attached to the telescope. When using a camera, however,
you should always wear corrective lenses to ensure the sharpest possible focus. If you
have astigmatism, corrective lenses must be worn at all times.
Focusing
The finder is mounted in the bracket and only needs to be attached to the telescope.
On the back of the telescope tube, just above the focusing knobs, there is a small
bracket with a regular head screw in it. This is where the finder bracket is mounted.
To install the finderscope:
1. Locate the mounting bracket near the back of the telescope tube.
2. Loosen the regular head screw from the mounting bracket on the telescope.
3. Slide the finder bracket onto the bracket on the telescope. The finder bracket will
slide in from the back. Orient the finder so that the objective lens is toward the
objective end of the telescope.
4. Tighten the regular head screw on the bracket to hold the finder in place.
Attaching the Finder