Focusing - Celestron C4.5 Instruction Manual

Focusing To focus your telescope, simply turn either of the focus knobs located
directly below the eyepiece holder (see figure 4-2). Turning the knobs
clockwise allows you to focus on an object that is farther than the one you are
currently observing. Turning the knob counterclockwise from you allows
you to focus on an object closer than the one you are currently observing.
In addition to understanding how the focusing mechanism works, there are a
few focusing hints that should be remembered when using any optical
instrument.
20 œ Getting Started
Never try to look through glass. Glass found in household windows may
vary in thickness from one location to the next, and as a result, is optically
imperfect. 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
focus. 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 roof tops.
Hazy skies, fog and mist can also make it difficult to focus. The amount
of detail that can be seen under these conditions will be greatly reduced.
When using your telescope as a telephoto lens, the split screen focuser of
the 35mm camera may "black out." This is common with all long focal
length lenses. If this does happen, use the ground glass portion of your
focusing screen. To achieve a very sharp focus, consider using a focusing
magnifier. (These are readily available from your local camera store.)
If you wear corrective lenses (specifically glasses), you may want to
remove them when observing with an eyepiece attached to the telescope.
However, when using a camera you should always wear corrective lenses
to ensure the sharpest possible focus. If you have astigmatism, corrective
lenses must be worm at all times.
Focus Knobs