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A. Introducing the Meade Model 390
The Model 390 is an easy-to-operate, high performance 90mm refracting telescope,
intended for astronomical and terrestrial (land) observing. Equipped with
a deluxe altazimuth mount and aluminum tripod, the telescope's motion is
adjustable over a wide range for tracking celestial or land objects. Your
telescope comes to you ready for adventure; it will be your companion in
a universe of breathtaking landscapes, planets, galaxies, and stars.
Fig. 1: Meade Model 390: 90mm Altazimuth Refracting Telescope
1. Tripod legs
2. Altazimuth mount
3. Altitude flexible cable control
4. Azimuth flexible cable control
5. Azimuth lock
6. Azimuth base
7. Azimuth shaft bolt
8. Optical tube assembly
9. Optical tube saddle plate
10. Cradle rings
11. Cradle ring lock knobs
12. Diagonal mirror
14. Focuser thumbscrew
15. Focus knobs
17. Diagonal thumbscrew
18. 6 x 30 viewfinder
19. Telescope front dust cover
20. Viewfinder bracket thumbscrews
21. Viewfinder bracket
22. Dew shield
23. Objective lens cell
24. Altitude shaft acorn cap nut
25. Tripod leg Phillips-head fastener screws
26. Tripod leg bolt 1/2" nuts
27. Accessory shelf central mounting knob
28. Accessory shelf
29. Leg brace supports
30. Tripod leg lock knobs
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1. This Manual
These instructions detail the set-up, operation, specifications, and optional
accessories of your Meade Model 390. In order that you may achieve maximum
enjoyment of the instrument, we urge that you take a few minutes to read
all of this manual before making first observations through the telescope.
As you read this manual, the technical terms associated with telescopes
will be made clear.
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2. Standard Equipment
—Complete optical tube assembly with multi-coated 90mm diameter objective
lens, dew shield, cradle rings, viewfinder bracket, and 1.25" rack
and pinion focuser. Lens focal length = 1000mm; f/11.
—Altazimuth mount with pre-attached heavy duty, continuously adjustable,
aluminum tripod and leg braces.
MA 25mm (40x) eyepiece (1.25" O.D. )
Diagonal mirror (1.25" O.D.)
Flexible cable controls for both telescope axes
Accessory shelf with mounting knob
6 x 30 viewfinder
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B. Unpacking and Assembly
(Numbers in brackets refer to Fig. 1.)
Your Meade Model 390 comes to you packaged almost entirely pre-assembled.
You will find upon opening the giftbox that there are two compartments within
that contain the optical tube assembly and the tripod with equatorial mount.
The accessories described above will be located within compartments custom-cut
into the styrofoam block inserts. (References herein, e.g., (6)—are
to Fig.1 unless otherwise specified.)
—Remove and identify the telescope's Standard Equipment listed in Section
—The three tripod lock knobs (30) have been removed from the bottom section
of each tripod leg to insure safe arrival of the tripod assembly. To install,
thread in each tripod lock knob into the threaded hole located at the right
side of each of the three gray colored castings (see illustration, below)
at the bottom of each tripod leg. Tighten the tripod lock knob only to a
"firm feel" to avoid damage to the tripod caused by overtightening.
—Spread the tripod legs (1) to full extension so that the leg braces
(29) are taut (should one of the tripod leg braces slip out of the center
triangle fastener, merely reposition the brace and slide it back into position).
Adjust the tripod with the attached mount (2) to the desired height by loosening
the tripod lock knobs and extend the sliding inner section of each tripod
leg; then tighten each knob.
—Remove the mounting knob from the round accessory shelf (28). Place the
accessory shelf on top of the center triangle leg brace fastener of the
tripod so that the threaded stud protruding from the bottom of the shelf
passes through the hole in the center. Then replace and tighten the accessory
shelf mounting knob (27).
—Attach the flexible cable controls (3) and (4). These cable controls are
secured in place with a firm tightening of the thumbscrew located at the
end of each cable.
—The viewfinder bracket (21) comes pre-attached to the optical tube, but
the viewfinder (18) is shipped separately. Place the viewfinder into the
viewfinder bracket rings by backing off the thumbscrews. Then center the
viewfinder in both bracket rings using the three thumbscrews (20) on each
bracket ring. Orient the viewfinder so its front objective lens is pointing
in the same direction as the main telescope's objective lens (23).
—While firmly holding the optical tube (8), position it onto the optical
tube saddle plate (9), with the midpoint of the optical tube's length lying
roughly in the center of the saddle plate. Then slide the cradle rings (10)
over the saddle plate of the mount. Tighten the cradle lock knobs (11) to
a firm feel. Do not overtighten these knobs. Make sure the focuser mechanism
is on the same side as the slow-motion controls.
—Insert the diagonal mirror (12) into the focuser (13), and tighten the
focuser thumbscrew (14), to secure the diagonal mirror.
—Insert the MA25mm eyepiece (16) into the diagonal mirror, and tighten
the diagonal thumbscrew (17) to secure the eyepiece.
The telescope is now fully assembled. Before it can be properly used, however,
the telescope must be balanced and the viewfinder aligned.
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1. Balancing the Telescope
In order for the telescope to move smoothly on its mechanical axes, it must
first be balanced on the saddle plate. All motions of the altazimuth telescope
(more on this later) take place by moving about these two axes; altitude
(up-and-down motion), and azimuth (side-to-side motion) separately or simultaneously.
To obtain a fine balance of the telescope, follow the method below:
—Loosen the cradle ring lock knobs (11) so that the main tube (8) in the
cradle rings (10) slides easily up-or-down in the cradle rings. Move the
main tube in the cradle rings until it is balanced on the saddle (9). Re-lock
the knobs (11).
The telescope is now properly balanced.
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2. Alignment of the Viewfinder
The wide field of view provided by the 6 x 30mm viewfinder permits easy
object sighting prior to observation in the higher-power main telescope.
The 6 x 30 Viewfinder (18) must be attached to the viewfinder bracket (21)
as seen in Fig. 1. In order for the viewfinder to be functional, however,
it must be aligned to the main telescope, so that both the viewfinder and
main telescope point at the same position in the sky. With this simple alignment
performed, finding objects is greatly facilitated, since you will first
locate an object in the wide-field viewfinder, then you will look in the
eyepiece of the main telescope for a detailed view. To align the viewfinder
follow these steps:
—Remove the telescope front dust cover (19), and the dust covers of the
—Place the low-power (MA25mm) eyepiece into the focuser of the main telescope.
—Unlock the Azimuth lock (5) so that the telescope turns on both axes.
(Note: The altitude axis is a clutched mechanism that does not require locking
or unlocking to allow movement.) To move the Model 390 in altitude (up or
down), merely grasp the rear portion of the telescope optical tube assembly
(8) and apply a small amount of force in the up or down direction desired.
Point the main telescope at some well-defined land object (e.g., the top
of a telephone pole) at least 200 yards distant, and re-lock the azimuth
lock (5). Turn the flexible cable controls, (3) and (4), to center the object
in the telescopic field.
—With the front of the viewfinder already centered in the front bracket
ring, look through the viewfinder and loosen or tighten, as appropriate,
one or more of the rear viewfinder bracket ring thumbscrews (26) until the
viewfinder's crosshairs are likewise centered on the object previously centered
in the main telescope.
—Check this alignment on a celestial object, such as a bright star or the
Moon, and make any refinements necessary, using the method outlined above.
With this alignment performed, objects first located in the wide-field of
the viewfinder will also be centered in the main telescope's field of view.
(Note: The viewfinder presents an image which is upside-down; this orientation
is customary in astronomical viewfinders.)
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C. Using the Telescope
With the telescope assembled, and balanced as described above, you are ready
to begin observations. Decide on an easy-to-find object such as the Moon,
if it is visible, or a distant land object to become accustomed to the functions
and operations of the telescope. For the best results during observations,
follow the suggestions below:
—To center an object in the main telescope, loosen the telescope's Azimuth
lock (5) . The telescope can now turn on its axes. Use the aligned viewfinder
to first sight-in on the object you wish to observe; with the object centered
on the viewfinder's crosshairs, re-tighten the Azimuth lock. Then turn the
Altitude and Azimuth flexible cable controls (3) and (4) for any fine centering
Note: It is possible to "run out"
of adjustment when using the flexible cable controls (3) and (4). If this
occurs, turn the flexible cable control until the Altitude or Azimuth tangent
assembly is in the middle of its travel. Re-center the object you wish to
observe by releasing the Azimuth lock (5) and move the telescope up, down,
or side-to-side by grasping the rear portion of the telescope optical tube
assembly (8) and apply a small amount of force in the direction desired.
Turn the Altitude and Azimuth flexible cable controls (3) and (4) for fine
—If you have purchased an assortment of eyepieces, always start an observation
session with a lower power eyepiece (e.g., MA 25mm eyepiece); get the
object well-centered in the field of view and sharply focused. Then try
the next step up in magnification. If the image starts to become fuzzy as
you work into higher magnifications, then back down to a lower power; the
atmospheric steadiness is not sufficient to support high powers at the time
you are observing. Keep in mind that a bright, clearly resolved but smaller
image will show far more detail than a dimmer, poorly resolved larger image.
The MA 25mm eyepiece included with the Model 390 presents a wide field of
view, ideal for general observing of land objects, clusters of stars, nebulae,
and galaxies. It is also probably the best eyepiece to use in the initial
finding and centering of any object.
—Once centered, the object can be focused by turning one of the knobs of
the focusing mechanism (15). You will notice that an astronomical object
in the field of view will begin to slowly move across the eyepiece field.
This motion is caused by the rotation of the Earth on its axis, although
the planets and stars, are, for practical purposes, fixed in their positions
in the sky. The platform on which the telescope is sitting ( the Earth)
rotates once every 24 hours under these objects. To keep astronomical
objects centered in the field of the telescope, simply turn one or both
of the Altitude and Azimuth flexible cable controls (3) and (4). Objects
will appear to move through the field more rapidly at higher powers.
—Avoid touching the eyepiece while observing through the telescope. Vibrations
resulting from such contact will cause the image to move. Likewise, avoid
observing sites where ground-based vibrations may resonate the tripod. Viewing
from the upper floors of a building may also introduce image movement.
—You should allow a few minutes to allow your eyes to become "dark
adapted" before attempting any serious astronomical observations. Use
a red filtered flashlight to protect your night vision when reading star
maps or inspecting the components of the telescope.
—Avoid setting up the telescope inside a room and observing through an
open window (or worse yet, a closed window). Images viewed in such a manner
may appear blurred or distorted due to temperature differences between inside
and outside air. Also, it is a good idea to allow your telescope a chance
to reach the ambient (surrounding) outside temperature before starting an
—Avoid viewing objects low on the horizon. Objects will appear better
resolved with far greater contrast when viewed higher in the sky. Also,
if images appear to "shimmer" in the eyepiece, reduce power
until the image steadies. This condition is caused by air turbulence in
the upper atmosphere.
The Meade Model 390 may be used for a lifetime of rewarding terrestrial
and astronomical observing, but basic to your enjoyment of the telescope
is a good understanding of the instrument. Read the above instructions carefully
until you understand all of the telescope's parts and functions. One or
two observing sessions will serve to clarify these points forever in your
The number of fascinating objects visible through your Meade refractor is
limited only by your own motivation. Astronomical software such as Meade's
AstroSearch, or a good star atlas such as the Meade Star Charts
will assist you in locating many interesting celestial objects. These
objects would include:
- Cloud belts across the surface of the planet Jupiter.
- The 4 major satellites of Jupiter, visible in rotation about the planet,
with the satellite positions changing each night.
- Saturn and its famous ring system, as well as several satellites of
Saturn, much fainter than the major satellites of Jupiter.
- The Moon: A veritable treasury of craters, mountain ranges and fault
lines. The best contrast for viewing the Moon is during its crescent phase.
The contrast during the full Moon phase is low due to the angle of illumination.
- Deep-Space: Nebulae, galaxies, multiple star systems, star clusters
hundreds of such objects are visible through the Model 390.
- Terrestrial objects: Your Meade Model 390 may be used for high-resolution
land viewing. In this case note that the diagonal mirror results in an image
which is reversed left-for-right, but which is correctly oriented up and
down. For a fully-corrected image, the optional Meade #928 45° Erect-Image Roof
Prism is required. Terrestrial observations should almost always be made
using a low-power eyepiece (50X or less), for bright sharp images. Beyond
the 50X-limit, images may appear ill-defined due to the fact that the images
are being viewed through the thickest and most turbulent part of the atmosphere,
unlike astronomical observations made by pointing the telescope up and through
a thinner atmosphere.
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D. Calculating Power
The power, or magnification, of the telescope depends on two optical characteristics:
the focal length of the main telescope and the focal length of the eyepiece
used during a particular observation. For example, the focal length of the
Model 390 telescope is fixed at 1000mm. To calculate the power in use with
a particular eyepiece, divide the focal length of the eyepiece into the
focal length of the main telescope. For example, using the MA 25mm eyepiece
supplied with the Model 390, the power is calculated as follows:
Meade Instruments manufactures several types of eyepiece designs that
are available for your telescope. The type of eyepiece ("SP"
Super Plössl, etc.) has no bearing on magnifying power but does affect
such optical characteristics as field of view, flatness of field, eye-relief,
and color correction.
The maximum practical magnification is determined by the nature of the object
being observed and, most importantly, by the prevailing atmospheric conditions.
Under very steady atmospheric "seeing," the Model 390 may be used
at powers up to about 250X on astronomical objects. Generally, however,
lower powers of perhaps 75X to 175X will be the maximum permissible, consistent
with high image resolution. When unsteady air conditions prevail (as witnessed
by rapid "twinkling" of the stars), extremely high-power eyepieces
result in "empty magnification," where the object detail observed
is actually diminished by the excessive power. Under such conditions
a planet may appear as a featureless fuzzy orb of bright light.
Accessory eyepieces are available both to increase and decrease the operating
eyepiece power of the telescope. If the Model 390 is used on a regular basis,
a selection of four to five eyepieces is a worthwhile investment to get
the best performance from your telescope. For example, an eyepiece assortment
of focal lengths 32mm or 40mm, 25mm, 12.5mm, 9mm, and 6mm yields a magnifying
range of 31x or 25x, 40x, 80x, 111x, and 167x respectively. A high quality
Barlow Lens, such as the Meade #126 2x Telenegative Barlow Lens, serves
to double the power of each of these eyepieces. To use the Barlow Lens,
insert the #126 unit into the telescope's focuser first, then insert the
diagonal mirror, followed by an eyepiece; the power thus obtained is then
double the power obtained when the eyepiece is used alone. For example,
the MA 25mm eyepiece, when used in conjunction with the #126 2x Telenegative
Barlow Lens yields 80X.
As with any quality instrument, lens or mirror surfaces should be cleaned
as infrequently as possible. Multi-coated lens surfaces, in particular,
should be cleaned only when absolutely necessary. In all cases avoid touching
any lens surface. A little dust on the surface of a lens or mirror causes
negligible loss of performance and should not be considered reason to clean
the surface. When lens cleaning does become necessary, use a camel's hair
brush or compressed air gently to remove dust. If the telescope's
dust cover is replaced after each observing session, cleaning of the optics
will rarely be required. Note: remove the dew shield (22) to access the
objective lens (23) for cleaning.
Every Meade Model 390 Altazimuth mount and tripod is factory inspected for
proper fit and function prior to shipment. It is unlikely that you will
need to adjust or tighten these parts after receipt of the telescope. However,
if the instrument received unusually rough handling in shipment, it is possible
that some of these assemblies can be loose. To make adjustments you will
need 1/2", 11/16", and/or 3/4" socket or adjustable end wrenches,
and a Phillips-head screwdriver.
The Altazimuth mount has two main areas that can be adjusted: A loose Altitude
shaft can be tightened by turning the Altitude shaft 3/4" acorn cap
nut (24) clockwise to a firm feel. A loose Azimuth base (6), can be tightened
by turning the 11/16" Azimuth shaft bolt (7), that is located underneath
the mount and in between the three tripod legs, clockwise to a firm feel.
Note that overtightening of any of the nuts or bolts can inhibit the smooth
rotating action of the axes and gears, and may result in stripping the threads.
The tripod legs have 1/2" nuts (26), and Phillips-head screws (25)
that may have backed off; these may also be tightened to a firm feel for
the most sturdy performance of the telescope.