Choosing An Eyepiece - Meade StarNavigator Series Instruction Manual

Intensity Slider
Fig. 13: Red Dot Viewfinder
intensity slider. Slide the
switch to the right to turn on
the viewfinder. The switch
provides two levels of
intensity for the red dot.
NEVER
point the
telescope
directly at
or near the Sun at any
time! Observing the
Sun, even for the
smallest fraction of a
second, will result in
instant and irreversible
eye damage, as well as
physical damage to
the telescope itself.
Fig. 15: 26 mm and
9.7 mm eyepieces.

Choosing an Eyepiece

A telescope's eyepiece magnifies the light gathered by the optical tube. Each eyepiece has a
focal length, expressed in millimetres, or "mm." The smaller the focal length, the higher the
magnification. For example, an eyepiece with a focal length of 9 mm has a higher magnification
than an eyepiece with a focal length of 25 mm.
Your telescope comes supplied with a low-powered 25 mm or 26 mm eyepiece which gives a
wide, comfortable field of view with high image resolution. Always begin your observations with
this eyepiece.
Low power eyepieces offer a wide field of view, bright, high-contrast images, and eye relief
during long observing sessions. After an object is located and centred in the eyepiece, try
switching to a higher power eyepiece to enlarge the image.
Viewing conditions vary nightly and depend on the site. Turbulence in the air,
NOTE:
even on an apparently clear night, can distort images. If an image appears fuzzy and
ill-defined, return to a lower power eyepiece for a more well-resolved image.
The power, or magnification of a telescope is determined by the focal length of the telescope
and the focal length of the eyepiece being used. To calculate eyepiece power, divide the
telescope's focal length by the eyepiece's focal length. For example, you may wish to use a
25 mm eyepiece with the StarNavigator102. Look up the focal length of the StarNavigator102
under
SPECIFICATIONS: StarNavigator102
Telescope focal length divided by Eyepiece focal length = Eyepiece power
800 Ö 25 = 32
The eyepiece power, or magnification is
therefore 32X (approximately).
Looking at or near the Sun will cause irreversible damage to your eye. Do not point this telescope at or near the Sun.
Do not look through the telescope as it is moving.
, page 36. The focal length is listed as 800 mm.
Too Much Power?
Can you ever have too much power? If you're
referring to eyepiece power (magnification),
yes, you can! The most common beginner's
mistake is to "overpower" a telescope by using
too high of a magnification, which the
telescope's
conditions cannot reasonably support. Keep
in mind that a smaller, but bright and well-
resolved image is far superior to one that is
larger, but dim and poorly resolved (see
below). Powers above 200X should be
employed
atmospheric conditions.
Audiostar can calculate the best eyepiece for
you to use. Try out the "Eyepiece Calc" feature
in the Utilities menu.
Most observers should have three or four
additional eyepieces to achieve the full range
of reasonable magnifications possible with the
StarNavigator telescopes. See "OPTIONAL
ACCESSORIES," page 32.
Fig. 14a & 14b: Jupiter; example of too much
magnification.
13
aperture and atmospheric
only under the steadiest