Celestron OMNI XLT 102 用户手册
28
Pointing at Sigma Octantis
This method utilizes Sigma Octantis as a guidepost to the celestial pole. Since Sigma Octantis is about 1° degree
from the south celestial pole, you can simply point the polar axis of your telescope at Sigma Octantis.. Although
this is by no means perfect alignment, it does get you within one degree. Unlike the previous method, this must
be done in the dark when Sigma Octantis is visible. Sigma Octantis has a magnitude of 5.5 and may be difficult to
see and a binocular may be helpful as well as the finderscope.
1. Set the telescope up so that the polar axis is pointing south.
2. Loosen the DEC clutch knob and move the telescope so that the tube is
from the south celestial pole, you can simply point the polar axis of your telescope at Sigma Octantis.. Although
this is by no means perfect alignment, it does get you within one degree. Unlike the previous method, this must
be done in the dark when Sigma Octantis is visible. Sigma Octantis has a magnitude of 5.5 and may be difficult to
see and a binocular may be helpful as well as the finderscope.
1. Set the telescope up so that the polar axis is pointing south.
2. Loosen the DEC clutch knob and move the telescope so that the tube is
parallel to the polar axis. When this is done, the declination setting circle
will read 90°. If the declination setting circle is not aligned, move the
telescope so that the tube is parallel to the polar axis.
will read 90°. If the declination setting circle is not aligned, move the
telescope so that the tube is parallel to the polar axis.
3. Adjust the mount in altitude and/or azimuth until Sigma Octantis is in the
field of view of the finder.
4. If the above is done correctly, you should be able to observe near the
pole through the finderscope and a low power eyepiece.
Remember, while Polar aligning, do NOT move the telescope in R.A. or
DEC. You do not want to move the telescope itself, but the polar axis.
The telescope is used simply to see where the polar axis is pointing.
DEC. You do not want to move the telescope itself, but the polar axis.
The telescope is used simply to see where the polar axis is pointing.
Like the previous method, this gets you close to the pole but not directly on it.
F
F
i
i
n
n
d
d
i
i
n
n
g
g
t
t
h
h
e
e
S
S
o
o
u
u
t
t
h
h
C
C
e
e
l
l
e
e
s
s
t
t
i
i
a
a
l
l
P
P
o
o
l
l
e
e
(
(
S
S
C
C
P
P
)
)
This method helps improve your polar alignment and gets you closer to the pole that the above methods. This will
improve your accuracy for more serious observations and photography.
In each hemisphere, there is a point in the sky around which all the other stars appear to rotate. These points are
called the celestial poles and are named for the hemisphere in which they reside. For example, in the southern
hemisphere all stars move around the south celestial pole. When the telescope's polar axis is pointed at the
celestial pole, it is parallel to the Earth's rotational axis.
Many methods of polar alignment require that you
know how to find the celestial pole by identifying
stars in the area. Observers in the southern
hemisphere are not as fortunate as those in the
northern hemisphere. The stars around the south
celestial pole are not nearly as bright as those around
the north celestial pole. The closest star that is
relatively bright is Sigma Octantis. This star is just
within naked eye limit (magnitude 5.5) and lies about
1° from the south celestial pole but can be difficult to
locate.
know how to find the celestial pole by identifying
stars in the area. Observers in the southern
hemisphere are not as fortunate as those in the
northern hemisphere. The stars around the south
celestial pole are not nearly as bright as those around
the north celestial pole. The closest star that is
relatively bright is Sigma Octantis. This star is just
within naked eye limit (magnitude 5.5) and lies about
1° from the south celestial pole but can be difficult to
locate.
Figure
4-9
Therefore, with this method, you will use star patterns to find the south celestial pole. Draw an imaginary line
toward the SCP through Alpha Crucis and Beta Crucis (which are in the Southern Cross). Draw another
imaginary line toward the SCP at a right angle to a line connecting Alpha Centauri and Beta Centauri. The
intersecting of these two imaginary lines will point you close to the south celestial pole.
Figure 4-8
Sigma Octantis
Southern Cross
SCP
Southern Cross
SCP
Alpha Centauri
Beta Centauri
Beta Crucis
Omega
Octanis
Alpha Crucis
SCP