Orion SKYVIEW PRO 120 EQ - Manual (Page 8)

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knob. But first the R.A. axis of the mount must be aligned with
the Earth’s rotational (polar) axis—a process called polar
alignment.
Polar alignment
For Northern Hemisphere observers, approximate polar align-
ment is achieved by pointing the mount’s right ascension axis
at the North Star, or Polaris. It lies within 1° of the north celes-
tial pole (NCP), which is an extension of the Earth’s rotational
axis out into space. Stars in the Northern Hemisphere appear
to revolve around the NCP.
To find Polaris in the sky, look north and locate the pattern
of the Big Dipper (Figure 7). The two stars at the end of the
“bowl” of the Big Dipper point right to Polaris.
Observers in the Southern Hemisphere aren’t so fortunate to
have a bright star so near the south celestial pole (SCP). The
star Sigma Octantis lies about 1° from the SCP, but it is barely
visible with the naked eye (magnitude 5.5).
For general visual observation, an approximate polar align-
ment is sufficient.
1. Level the equatorial mount by adjusting the length of the
three tripod legs.
2. There are two latitude adjustment L-bolts (see Figure 6);
loosen one while tightening the other. By doing this you
will adjust the latitude of the mount. Continue adjusting the
mount until the pointer on the latitude scale is set at the
latitude of your observing site. If you don’t know your lati-
tude, consult a geographical atlas to find it. For example, if
your latitude is 35° North, set the pointer to 35. 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 lever and rotate the telescope’s opti-
cal tube until it is parallel with the right ascension axis, as
it is in Figure 6.
4. Move the tripod so the telescope tube and right ascen-
sion axis point roughly at Polaris. If you cannot see Polaris
Figure 8. For polar alignment, position the tripod so that the
"N" label at the base of the mount faces north. The azimuth fine
adjustment knobs above it are used to make small adjustments to the
mount’s azimuth position. Be certain to loosen the tripod attachment
knob on the central support shaft before adjusting these knobs.
Azimuth
adjustment
knobs
Figure 7. To find Polaris in the night sky, look north and find the
Big Dipper. Extend an imaginary line from the two “Pointer Stars”
in the bowl of the Big Dipper. Go about five times the distance
between those stars and you'll reach Polaris, which lies within 1° of
the north celestial pole (NCP).
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
Cassiopeia
N.C.P.
Pointer
Stars
Polaris
Figure 6. The SkyView Pro 120 equatorial mount.
R.A. setting circle
Polar axis finder
scope (optional)
Latitude scale
(opposite side)
Latitude
adjustment
L-bolts
Dec. slow-motion
control knob
Dec. setting circle
Dec. lock lever
Front opening
R.A. lock lever
R.A. slow-motion
control knob
Declination
Axis
Right
Ascension Axis