Loading ...
Loading ...
Loading ...
8
telescope’s eyepiece. If the EZ Finder II is properly aligned, the
object should be visible somewhere in the eld of view. Once the
object is visible in the eyepiece, use the slow-motion controls to
center it in the eld of view.
The Dec. slow-motion control cable can move the telescope a
maximum of 25°. This is because the Dec. slow-motion mecha-
nism has a limited range of mechanical travel. (The R.A. slow-
motion mechanism has no limit to its amount of travel.) If you
can no longer rotate the Dec. control cable in a desired direc-
tion, you have reached the end of travel, and the slow-motion
mechanism must be reset. This is done by rst rotating the con-
trol cable several turns in the opposite direction from which it was
being turned. Then, manually slew the telescope closer to the
object you wish to observe (remember to rst loosen the Dec.
lock knob). You should now be able to use the Dec. slow-motion
control cable again to ne adjust the telescope’s position.
Tracking Celestial Objects
When you observe a celestial object through the telescope, you’ll
see it drift slowly across the eld of view. To keep it in the eld,
assuming your equatorial mount is polar aligned, just turn the
R.A. slow-motion control cable clockwise. The Dec. slow-motion
control cable is not needed for tracking. Objects will appear to
move faster at higher magnications, because the eld of view
is narrower.
Optional Electronic Drives for Automatic
Tracking
An optional DC electronic drive can be mounted on the R.A. axis
of the equatorial mount to provide hands-free tracking. Objects
will then remain stationary in the eld of view without any manual
adjustment of the R.A. slow-motion control cable.
Understanding the Setting Circles
The setting circles on an equatorial mount enable you to
locate celestial objects by their “celestial coordinates”. Every
object resides in a specic location on the “celestial sphere”.
That location is denoted by two numbers: its right ascension
(R.A.) and declination (Dec.). In the same way, every location
on Earth can be described by its longitude and latitude. R.A.
is similar to longitude on Earth, and Dec. is similar to latitude.
The R.A. and Dec. values for celestial objects can be found in
any star atlas or star catalog.
The mount’s R.A. setting circle is scaled in hours, from 1 through
24, with small marks in between representing 10-minute incre-
ments. The numbers closest to the R.A. axis gear apply to view-
ing in the Southern Hemisphere, while the numbers above them
apply to viewing in the Northern Hemisphere.
The Dec. setting circle is scaled in degrees, with each mark rep-
resenting 2.5° increments. Values of Dec. coordinates range from
+90° to -90°. The 0° mark indicates the celestial equator. When
the telescope is pointed north of the celestial equator, values of
the Dec. setting circle are positive, while when the telescope is
pointed south of the celestial equator, values of the Dec. setting
circle are negative.
So, the coordinates for the Orion Nebula listed in a star atlas will
look like this:
R.A. 5h 35.4m Dec. -5° 27’
That’s 5 hours and 35.4 minutes in right ascension, and -5
degrees and 27 arc-minutes in declination (there are 60 arc-min-
utes in 1 degree of declination).
Before you can use the setting circles to locate objects, the
mount must be properly polar aligned, and the R.A. setting circle
must be calibrated. The Dec. setting circle has been permanently
calibrated at the factory, and should read 90° whenever the tele-
scope optical tube is parallel with the R.A. axis.
Calibrating the Right Ascension Setting Circle
1. Identify a bright star in the sky near the celestial equator
(Dec. = 0°) and look up its coordinates in a star atlas.
2. Loosen the R.A. and Dec. lock knobs on the equatorial
mount, so the telescope optical tube can move freely.
3. Point the telescope at the bright star whose coordinates
you know. Lock the R.A. and Dec. lock knobs. Center the
star in the telescope’s eld of view with the slow-motion
control cables.
4. Rotate the setting circle until the metal arrow indicates the
R.A. coordinate listed in the star atlas for the object.
Finding Objects with the Setting Circles
1. Now that both setting circles are calibrated, look up in a
star atlas the coordinates of an object you wish to view.
2. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Remember to use the upper set
of numbers on the R.A. setting circle. Retighten the lock
knob.
3. Loosen the Dec. lock knob and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Remember that values of the Dec.
setting circle are positive when the telescope is pointing
north of the celestial equator (Dec. = 0°), and negative
when the telescope is pointing south of the celestial equa-
tor. Retighten the lock knob.
Most setting circles are not accurate enough to put an object
dead-center in the telescope’s eyepiece, but they should place
the object somewhere within the eld of view of the EZ Finder II,
assuming the equatorial mount is accurately polar aligned. Use
the slow-motion controls to center the object in the reex sight,
and it should appear in the telescope’s eld of view.
The R.A. setting circle must be re-calibrated every time you wish
to locate a new object. Do so by calibrating the setting circle for
the centered object before moving on to the next one.
Confused About Pointing the Telescope?
Beginners occasionally experience some confusion about how
to point the telescope overhead or in other directions. In Figure
1a the telescope is pointed north, as it would be during polar
alignment. The counterweight shaft is oriented downward. But
it will not look like that when the telescope is pointed in other
directions. Let’s say you want to view an object that is directly
overhead, at the zenith. How do you do it?
Loading ...
Loading ...
Loading ...