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1. Your First Observations
|IMPORTANT NOTICE! Never use a telescope or spotting scope to look at the Sun! Observing the Sun, even for the shortest fraction of a second, will cause irreversible damage to your eye as well as physical damage to the telescope or spotting scope itself. |
With the telescope assembled as described in Section B, and with the diagonal
mirror and eyepiece in place, you are ready to make observations through
the telescope. Even without the viewfinder (if not yet installed), terrestrial
objects will be fairly easy to locate and center in the telescope's field
of view with a low power eyepiece, by "gunsighting" along the
side of the main telescope tube.
By unlocking the R.A. lock (8, Fig. 4), the telescope may be turned
rapidly through wide angles in Right Ascension (R.A.). The reason for the
terminology "Right Ascension" and its complementary term, "Declination"
will be made clear further on in this manual. Fine adjustments in R.A. are
made by turning the R.A. slow-motion knob (9, Fig. 4), while the R.A. lock
is in the "locked" position.
Releasing the Declination lock (5, Fig. 4), permits sweeping the telescope
rapidly through wide angles in Declination.
To use the Declination fine-adjust, or slow-motion control, lock the telescope
in Declination using the Declination lock, and turn the Declination slow-motion
knob. (7, Fig. 4).
With the above mechanical operations in mind, select an easy-to-find terrestrial
object as your first telescope subject for example, a house or building
perhaps one-half mile distant.
Unlock the Dec. lock, and R.A. lock, center the object in the telescopic
field of view and then re-lock the Dec. and R.A. locks. Precise image centering
is accomplished by using the Dec. and R.A. slow motion controls.
Note: The R.A. and Dec. slow motion control knobs cannot be used
when the optional #1697 CDS is operating. When
power is supplied to the telescope, use the CDS keypad
to make fine adjustments in R.A. or Declination. Forcing the manual control
knobs when the motors are powered can cause damage to the gear system.
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The focus knob (16, Fig. 4) allows focusing the image. Focusing the telescope
from its nearest possible focus point (on an object about 50 ft. to 150
ft., depending on the model) to an object at infinity requires a fairly large
movement of the focuser drawtube. The focuser is designed to provide an
extremely sensitive means of bringing an object into precise, sharp focus.
After a specific object has been brought into focus, closer objects require
moving the focuser drawtube outward; more distant objects require moving
the drawtube inward.
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The magnification, or power, of the telescope depends upon 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
4" f/9 telescope is fixed at 920mm; the focal length of the 7"
f/9 telescope is fixed at 1600mm. 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 SP26mm eyepiece supplied with
the 4" f/9, the power is calculated as follows:
Power = 920mm/26mm= 35X
The type of eyepiece (whether "MA" Modified Achromatic
or "PL" Plössl, "SP" Super Plössl, etc.) has
no bearing on magnifying power but does affect such optical characteristics
as field of view, flatness of field 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 4" APO may be
used at powers up to about 400X on astronomical objects, the 7" APO
up to about 700X. Generally, however, lower powers of perhaps 250X to 350X
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
When beginning observations on a particular object, start with a low power
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.
Accessories are available both to increase and decrease the operating eyepiece
power of the telescope. See your Meade dealer or the Meade General Catalog
for information on accessories.
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4. Apparent Field and Actual Field
Two terms that are often confused and misunderstood are "Apparent Field"
and "Actual Field." "Apparent Field" is a function of
the eyepiece design and is built into the eyepiece. While not totally accurate
(but a very good approximation), "Apparent Field" is usually thought
of as the angle your eye sees when looking through an eyepiece. "Actual
Field" is the amount of the sky that you actually see and is a function
of the eyepiece being used and the telescope.
The "Actual Field" of a telescope with a given eyepiece is calculated
by knowing the "Apparent Field" and power of an eyepiece with
a given telescope. The "Actual Field" of a telescope is calculated
by taking the "Apparent Field" of the eyepiece and dividing by
The following table lists the most common optional eyepieces available and
the "Apparent Field" for each eyepiece. The power and "Actual
Field" of view that each eyepiece yields is listed for each basic telescope
Table 2: Optional Eyepieces
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5. Celestial Coordinates: Declination and Right Ascension
Analogous to the Earth-based coordinate system of latitude and longitude,
celestial objects are mapped according to a coordinate system on the "celestial
sphere," the imaginary sphere on which all stars appear to be placed.
The Poles of the celestial coordinate system are defined as those 2 points
where the Earth's rotational axis, if extended to infinity, North and South,
intersect the celestial sphere. Thus, the North Celestial Pole is that point
in the sky where an extension of the Earth's axis through the North Pole
intersects the celestial sphere. In fact, this point in the sky is located
near the North Star, or Polaris.
On the surface of the Earth, "lines of longitude" are drawn between
the North and South Poles. Similarly, "lines of latitude" are
drawn in an East-West direction, parallel to the Earth's equator. The celestial
equator is simply a projection of the Earth's equator onto the celestial
sphere. Just as on the surface of the Earth, imaginary lines have been drawn
on the celestial sphere to form a coordinate grid. Celestial object positions
on the Earth's surface are specified by their latitude and longitude.
The celestial equivalent to Earth latitude is called "Declination,"
or simply "Dec.," and is measured in degrees, minutes or seconds
north ("+") or south ("-") of the celestial equator.
Thus any point on the celestial equator (which passes, for example, through
the constellations Orion, Virgo and Aquarius) is specified as having 0°0'0"
Declination. The Declination of the star Polaris, located very near the
North Celestial Pole, is +89.2°.
The celestial equivalent to Earth longitude is called "Right Ascension,"
or "R.A." and is measured in hours, minutes and seconds from an
arbitrarily defined "zero" line of R.A. passing through the constellation
Pegasus. Right Ascension coordinates range from 0hr0min0sec up to (but not
including) 24hr0min0sec. Thus there are 24 primary lines of R.A., located
at 15 degree intervals along the celestial equator. Objects located further
and further east of the prime (0h0m0s) Right Ascension grid line carry increasing
With all celestial objects therefore capable of being specified in position
by their celestial coordinates of Right Ascension and Declination, the task
of finding objects (in particular, faint objects) in the telescope is vastly
simplified. The setting circles of the LXD650 and LXD750 mounts included
with Meade apochromatic refractors may be dialed, in effect, to read the
object coordinates and the object found without resorting to visual location
techniques. However, these setting circles may be used to advantage only
if the telescope is first properly aligned with the North Celestial Pole.
Figure 7: The Celestial Pole
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6. Lining Up With the Celestial Pole
Objects in the sky appear to revolve around the celestial pole. (Actually,
celestial objects are essentially "fixed," and their apparent
motion is caused by the Earth's axial rotation). During any 24 hour period,
stars make one complete revolution about the pole, describing concentric
circles with the pole at the center. By lining up the telescope's polar
axis with the North Celestial Pole (or for observers located in Earth's
Southern Hemisphere with the South Celestial Pole) astronomical objects
may be followed, or tracked, simply by moving the telescope about one axis,
the polar axis. In the case of the Meade APO refractor telescopes, this
tracking may be accomplished automatically with optional electric motor
If the telescope is reasonably well aligned with the pole, therefore, very
little use of the telescope's Declination slow motion control is necessary; virtually
all of the required telescope tracking will be in Right Ascension. (If the
telescope were perfectly aligned with the pole, no Declination tracking
of stellar objects would be required). For the purposes of casual visual
telescopic observations, lining up the telescope's polar axis to within
a degree or two of the pole is more than sufficient: with this level of
pointing accuracy, one of the telescope's optional motor drives will track
accurately and keep objects in the telescopic field of view for perhaps
20 to 30 minutes.
Figure 8: Finding Polaris
Begin polar aligning the telescope as soon as you can see Polaris. Finding
Polaris is simple. Most people recognize the "Big Dipper." The
Big Dipper has two stars that point the way to Polaris (see Fig. 8). Once
Polaris is found, it is a straightforward procedure to obtain a rough polar
To line up the telescope with the Pole, follow this procedure:
1. Using the bubble level located on the pier cap, adjust the tripod legs
so that the telescope/tripod system reads "level."
At this point, your polar alignment is good enough for casual observations.
There are times, however, when you will need to have precise polar alignment,
such as when making fine astrophotographs or when using the setting circles
to find new objects.
2. Set the equatorial head to your observing latitude as described above.
3. Loosen the Dec. lock (5, Fig. 4), and rotate the telescope tube in Declination
so that the telescope's Declination reads 90°. Tighten the Dec. lock.
4. Using the Azimuth control knob (11, Fig. 5) and Latitude adjustment knob
(5, Fig. 5), center Polaris in the field of view. Do not use the telescope's
Declination or Right Ascension controls during this process.
As an aside procedure, during your first use of the telescope, you should
check the calibration of the Declination setting circle (6, Fig. 4). After
performing the polar alignment procedure, center the star Polaris in the
telescope field. Loosen slightly the knurled lock screw of the Declination
setting circle. Now turn the circle unit until it reads 89.2°, the
Declination of Polaris, and then tighten down the knurled lock screw, avoiding
any motion of the circle.
Once the latitude angle has been fixed and locked-in according to the
above procedure, it is not necessary to repeat this operation each time
the telescope is used, unless you move a considerable distance North or
South from your original observing position. (Approximately 70 miles movement
in North-South observing position is equivalent to 1° in latitude change).
The equatorial head may be detached from the field tripod and, as long as
the latitude angle setting is not altered and the field tripod is leveled,
it will retain the correct latitude setting when replaced on the tripod.
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7. Precise Polar Alignment
It should be emphasized that precise alignment of the telescope's polar
axis to the celestial pole for casual visual observations is not necessary.
Don't allow a time-consuming effort at lining up with the pole to interfere
with your basic enjoyment of the telescope. For long-exposure photography,
however, the ground rules are quite different, and precise polar alignment
is not only advisable, but almost essential.
Notwithstanding the precision and sophistication of the optional computer drive system
available for the Meade APO telescopes, the fewer tracking corrections required
during the course of a long-exposure photograph, the better. (For our purposes,
"long-exposure" means any photograph of about 10 minutes duration
or longer). In particular, the number of Declination corrections required
is a direct function of the precision of polar alignment.
Precise polar alignment requires the use of a crosshair eyepiece. Meade
Illuminated Reticle Eyepieces are well-suited in this application, but you
will want to increase the effective magnification through the use of a 2x
or 3x Barlow lens. Then follow this procedure, sometimes better known as
the "Drift" method:
1. Obtain a rough polar alignment as described earlier. Place the illuminated
reticle eyepiece (or eyepiece/Barlow combination) into the eyepiece holder
of the telescope.
The above procedure results in very accurate polar alignment, and minimizes
the need for tracking corrections during astrophotography.
2. Point the telescope, with the motor drive running, at a moderately bright
star near where the meridian (the North-South line passing through your
local zenith) and the celestial equator intersect. For best results, the
star should be located within ±30 minutes in R.A. of the meridian and
within ±5° of the celestial equator. (Pointing the telescope at
a star that is straight up, with the Declination set to 0°, will point
the telescope in the right direction.)
3. Note the extent of the star's drift in Declination (disregard drift in
Figure 9: Mount Too Far East
a. If the star drifts South (or down), the telescope's polar axis
is pointing too far East (Fig. 9).
Figure 10: Mount Too Far West
b. If the star drifts North (or up), the telescope's polar axis
is pointing too far West (Fig. 10).
4. Move the wedge in azimuth (horizontally) to effect the appropriate change
in polar alignment. Reposition the telescope's East-West polar axis orientation
until there is no further North-South drift by the star. Track the star
for a period of time to be certain that its Declination drift has ceased.
5. Next, point the telescope at another moderately bright star near the
Eastern horizon, but still near the celestial equator. For best results,
the star should be about 20° or 30° above the Eastern horizon
and within ± 5° of the celestial equator.
6. Again note the extent of the star's drift in Declination:
Figure 11: Mount Too Low
a. If the star drifts South, (or down) the telescope's polar axis
is pointing too low (Fig. 11).
Figure 12: Mount Too High
b. If the star drifts North, (or up) the telescope's polar axis
is pointing too high (Fig. 12).
7. Use the latitude angle fine-adjust control (5, Fig. 5) to effect the
appropriate change in latitude angle, based on your observations above.
Again, track the star for a period of time to be certain that Declination
drift has ceased.
In addition to the drift method described above, two optional accessories
can be used to achieve a precise polar alignment. The optional #814 Polar
Alignment Finder is a borescope device which uses an internal etched reticle
showing where to place the North Star to align the telescope. And the #1697
Computer Drive/Slew System has a computerized polar alignment routine that
automates the complete process, allowing very fast, precise polar alignment.
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8. Setting Circles
Setting circles included with Meade ED apochromatic telescopes and
equatorial mounts permit the location of faint celestial objects not easily
found by direct visual observation. With the telescope pointed at the North
Celestial Pole, the Dec. circle should read 90° (understood to mean
+90°). Objects located below the 0-0 line of the Dec. circle carry
minus Declination coordinates. Each division of the Dec. represents a 1°
increment. The R.A. circle runs from 0hr to (but not including) 24hr, and
reads in increments of 5min.
Note that the R.A. circle (17, Fig. 5) is double-indexed, i.e., there
are 2 series of numbers running in opposite directions around the circumference
of the R.A. circle. The upper series of numbers (increasing counterclockwise)
applies to observers located in the Earth's Northern Hemisphere;
the lower series of numbers (increasing clockwise) applies to observers
located in the Earth's Southern Hemisphere.
With the telescope aligned to the pole, center an object of known R.A. in
the telescopic field. Then turn the R.A circle, which can be rotated manually,
until the R.A. coordinate of the object is correctly indicated by the R.A.
pointer. As long as the telescope's motor drive remains "ON,"
the R.A. pointer will then correctly indicate the R.A. of any object at
which the telescope is pointed throughout the duration of the observing
To use the circles to locate a particular object, first look up the celestial
coordinates (R.A. and Dec.) of the object in a star atlas. Then loosen the
R.A. lock and turn the telescope to read the correct R.A. of the desired
object; lock the R.A. lock onto the object. Next, turn the telescope in
Declination to read the correct Declination of the object. If the procedure
has been followed carefully, and if the telescope was well-aligned with
the pole, the desired object should now be in the telescopic field of a
If you do not immediately see the object you are seeking, try searching
the adjacent sky area, using the R.A. and Dec. slow-motion controls to scan
the surrounding region. Keep in mind that with the 26mm eyepiece, the field
of view of the telescope is less than 1°. Because of its much wider
field, the viewfinder may be of significant assistance in locating and centering
objects, after the setting circles have been used to locate the approximate
position of the object.
Pinpoint application of the setting circles requires that the telescope
be precisely aligned with the pole. Refer to the preceding section on "Precise
Polar Alignment" for further details.
The setting circles may be used with or without the optional computer drive
system. As you track the object, whether by turning the R.A. slow-motion
control knob or using the optional computer drive system, the setting circles
keep position with the object.
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9. Observing with the Telescope
Meade APO telescopes permit an extremely wide array of serious observational
opportunities. Even in normal city conditions, with all of the related air
and light pollution, there are a good many interesting celestial objects
to observe. But to be sure, there is no substitute for the clear, steady,
dark skies generally found only away from urban environments, or on mountain
tops: objects previously viewed only in the city take on added detail or
are seen in wider extension, or even become visible at all for the first
The amateur astronomer is faced typically with two broadly defined problems
when viewing astronomical objects through the Earth's atmosphere: first
is the clarity, or transparency, of the air and, secondly the steadiness
of the air. This latter characteristic is often referred to as the quality
of "seeing." Amateur astronomers talk almost constantly about
the "seeing conditions," since, perhaps ironically, even the clearest,
darkest skies may be almost worthless for serious observations if the air
is not steady. This steadiness of the atmosphere is most readily gauged
by observing the "twinkling" of the stars: rapid twinkling implies
air motion in the Earth's atmosphere, and under these conditions resolution
of fine detail (on the surface of Jupiter, for instance) will generally
be limited. When the air is steady, stars appear to the naked eye as untwinkling
points of unchanging brightness and it is in such a situation that the full
potential of the telescope may be realized: higher powers may be used to
advantage, closer double stars are resolved as distinct points and fine
detail may be observed on the Moon and planets.
Several basic guidelines should be followed for best results in using your
1. Try not to touch the eyepiece while observing. Any vibrations resulting
from such contact will immediately cause the image to move.
2. Allow your eyes to become "dark adapted" prior to making serious
observations. Night adaptation generally requires about 10 to 15 minutes
for most people.
3. Let the telescope "cool down" to the outside environmental
temperature before making observations. Temperature differentials between
a warm house and cold outside air require about 30 minutes for the telescope's
optics to regain their true and correct figures. During this period, the
telescope will not perform well. A good idea is to take the telescope outside
30 minutes before you want to start observing.
4. If you wear glasses and do not suffer from astigmatism, take your glasses
off when observing through the telescope. You can re-focus the image to
suit your own eyes. Observers with astigmatism, however, should keep their
glasses on since the telescope cannot correct for this eye defect.
5. Avoid setting up the telescope inside a room and observing through an
open window (or worse yet, through a closed window!). The air currents caused
by inside/outside temperature differences will make quality optical performance
6. Perhaps most importantly of all, avoid "overpowering" your
telescope. The maximum usable magnification at any given time is governed
by seeing conditions. If the telescopic image starts to become fuzzy as
you increase in power, drop down to a reduced magnification. A smaller but
brighter and sharper image is far preferable to a larger but fuzzy and indistinct
7. As you use your telescope more and more, you will find that you are seeing
finer detail: observing through a large aperture telescope is a required
skill. Celestial observing will become increasingly rewarding as you eye becomes
better trained to the detection of subtle nuances of resolution.