6
2. Loosen the latitude lock knob and tilt the mount until the
pointer on the latitude scale is set at the latitude of your
observing site. For example, if your latitude is 40° North,
set the pointer to 40. Then retighten the latitude lock knob.
If you don’t know your latitude, consult a geographical
atlas to find it.The latitude setting should not have to be
adjusted again unless you move to a different viewing
location some distance away.
3. Loosen the Dec. lock knob and rotate the telescope optical
tube until it is parallel with the R.A. axis. The pointer on the
Dec. setting circle should read 90°. Retighten the Dec. lock
knob.
4. Next, loosen the azimuth lock knob at the base of the
equatorial mount. Rotate the entire equatorial mount in the
horizontal direction until the telescope (and the R.A. axis)
points roughly at Polaris. If you cannot see Polaris directly
from your observing site, consult a compass and rotate
the equatorial mount until the telescope points north.
Retighten the azimuth lock knob.
The equatorial mount is now polar aligned for casual observ-
ing. More precise polar alignment is required for
astrophotography. Several methods exist and are described in
many amateur astronomy reference books and astronomy
magazines.
Note: From this point on in your observing session, you
should not make any further adjustments in the azimuth
or the latitude of the mount, nor should you move the tri-
pod. Doing so will ruin the polar alignment. The telescope
should only be moved about its R.A. and Dec. axes.
tracking celestial objects
When you observe a celestial object through the telescope,
you’ll see it drift slowly across the field of view. To keep it in
the field, if your equatorial mount is polar aligned, just turn the
R.A. slow-motion control. The Dec. slow-motion control is not
needed for tracking. Objects will appear to move faster at
higher magnifications, because the field of view is narrower.
optional Motor Drive for automatic tracking
An inexpensive, optional AC motor drive (#17001) can be
mounted on the R.A. axis of the Observer 60 EQ Ultra, to
provide hands-free tracking. Objects remain stationary in the
field of view without any manual adjustment of the R.A. slow-
motion control.
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 specific location on the “celestial sphere,”
denoted by two numbers: its right ascension (R.A.) and decli-
nation (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 R.A. setting circle is scaled in hours, from 1 through 24,
with small hash marks in between representing 10-minute
increments (there are 60 minutes in 1 hour of R.A.). The num-
bers closest to the R.A. gear apply to viewing in the Southern
Hemisphere, while the numbers above them apply to viewing in
the Northern Hemisphere. The Dec. setting circle is scaled in
degrees (there are 60 arc-minutes in 1 degree of declination).
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 (the negative sign
denotes south of the celestial equator).
Before you can use the setting circles to locate objects, the
equatorial mount must be carefully polar aligned, and the set-
ting circles must be calibrated. The declination setting circle
was calibrated at the factory, and should read 90° when the
telescope optical tube is pointing exactly along the polar axis.
If it does not read 90°, it may have to be reset.
calibrating the right ascension setting circle
1. Identify a bright star near the celestial equator and look up
its coordinates in a star atlas.
2. Loosen the R.A. and Dec. lock knobs on the equatorial
mount (not the azimuth lock knob or latitude adjustment
knob), so the telescope optical tube can move freely.
3. Point the telescope at the bright star near the celestial
equator whose coordinates you know. Center the star in
the telescope’s field of view. Lock the R.A. and Dec. lock
knobs.
4. Rotate the R.A. setting circle so the pointer indicates the
R.A. listed for that object in the star atlas.
Finding objects With the setting circles
Now that both setting circles are calibrated, look up in a star
atlas the coordinates of an object you wish to view.
1. 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. Retighten the lock knob.
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. Retighten the lock knob.
Most setting circles are not accurate enough to put an object
dead-center in your finder scope’s field of view, but they’ll get
you close, assuming the equatorial mount is accurately polar-
aligned. 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.
6. using Your telescope—
astronomical observing
choosing an observing site
When selecting a location for observing, get as far away as
possible from direct artificial light such as street lights, porch
