Meade lx-90 Manual De Instruções
14
Choosing an Eyepiece
A telescope’s eyepiece magnifies the image formed by the telescope’s main optics. Each eye-
piece has a focal length, expressed in millimeters, or “mm.” The smaller the focal length, the
higher the magnification. For example, an eyepiece with a focal length of 9mm has a higher
magnification than an eyepiece with a focal length of 26mm.
piece has a focal length, expressed in millimeters, or “mm.” The smaller the focal length, the
higher the magnification. For example, an eyepiece with a focal length of 9mm has a higher
magnification than an eyepiece with a focal length of 26mm.
Your telescope comes supplied with a Super Plössl 26mm eyepiece which gives a wide, com-
fortable field of view with high image resolution.
fortable field of view with high image resolution.
Low power eyepieces offer a wide field of view, bright, high-contrast images, and eye relief dur-
ing long observing sessions. To find an object with a telescope, always start with a lower power
eyepiece such as the Super Plössl 26mm. When the object is located and centered in the eye-
piece, you may wish to switch to a higher power eyepiece to enlarge the image as much as
practical for prevailing seeing conditions. For information about optional eyepieces for the
LX90, see "OPTIONAL ACCESSORIES," page 39.
ing long observing sessions. To find an object with a telescope, always start with a lower power
eyepiece such as the Super Plössl 26mm. When the object is located and centered in the eye-
piece, you may wish to switch to a higher power eyepiece to enlarge the image as much as
practical for prevailing seeing conditions. For information about optional eyepieces for the
LX90, see "OPTIONAL ACCESSORIES," page 39.
NOTE:
Seeing conditions vary widely from night-to-night and site-to-site. Turbulence
in the air, even on an apparently clear night, can distort images. If an image
appears fuzzy and ill-defined, back off to a lower power eyepiece for a more well-
resolved image (Fig. 7a and 7b).
appears fuzzy and ill-defined, back off to a lower power eyepiece for a more well-
resolved image (Fig. 7a and 7b).
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 tele-
scope's focal length by the eyepiece's focal length. For example, a 26mm eyepiece is supplied
with the LX90. The focal length of the LX90 is 2000mm (see "Specifications," page 44).
and the focal length of the eyepiece being used. To calculate eyepiece power, divide the tele-
scope's focal length by the eyepiece's focal length. For example, a 26mm eyepiece is supplied
with the LX90. The focal length of the LX90 is 2000mm (see "Specifications," page 44).
Telescope Focal Length
2000mm
Eyepiece Focal Length
26mm
The eyepiece power, or magnification is therefore 77X (approximately).
Mounting and Adjusting the Viewfinder
To align the viewfinder, perform steps 1 through 5 during the daytime; perform step 6 at night.
1. Slide the track on the bottom of the viewfinder into the slot in the viewfinder mounting
assembly. See Fig. 6a. To secure the viewfinder to the mounting assembly, tighten the two
thumbscrews (Fig. 6a) to a firm feel only.
thumbscrews (Fig. 6a) to a firm feel only.
2.
If you have not already done so, insert the Super Plössl 26mm eyepiece into the diagonal
prism.
prism.
3.
Unlock the R.A. (9, Fig. 1) and Dec (6, Fig. 1) locks so that the telescope moves freely on
both axes.
both axes.
4.
Point the telescope at some well-defined and stationary land object at least 200 yards dis-
tant, such as the top of a telephone pole or street sign. Center the object in the telescope
eyepiece. Re-tighten the R.A. and Dec locks.
tant, such as the top of a telephone pole or street sign. Center the object in the telescope
eyepiece. Re-tighten the R.A. and Dec locks.
5.
Look through the viewfinder eyepiece (Fig. 6b) and loosen or tighten, as appropriate, one
or more of the viewfinder collimation screws (Fig. 6b) until the viewfinder crosshairs are
precisely centered on the object you previously centered in the telescope eyepiece.
or more of the viewfinder collimation screws (Fig. 6b) until the viewfinder crosshairs are
precisely centered on the object you previously centered in the telescope eyepiece.
6. Check this alignment on a celestial object, such as the Moon or a bright star, and make
any necessary refinements, using the method outlined in steps 3 and 4.
Eyepiece Power =
= 77X
=
NOTE:
For a list of mag-
nification ratings
of the eyepieces
available for the
LX90 telescope,
see "OPTIONAL
ACCESSORIES,"
page 39.
For a list of mag-
nification ratings
of the eyepieces
available for the
LX90 telescope,
see "OPTIONAL
ACCESSORIES,"
page 39.
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.
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. 6a: Viewfinder Assembly.
Collimation
Screws
Screws
Mounting
Slot
Slot
Thumbscrews
Viewfinder
Eyepiece
Eyepiece
Track
Fig. 6b: Viewfinder Assembly.