15
Fig.j
Southern Hemisphere
In the Southern Hemisphere you must align the mount to the
SCP by locating it's position with star patterns, without the
convenience of a nearby bright star. The closest star is the faint
5.5-mag. Sigma Octanis which is about one degree away. Two
sets of pointers which help to locate the SCP are alpha and
beta Crucis (in the Southern Cross) and a pointer running at a
right angle to a line connecting alpha and beta Centauri (Fig.j).
omega
Octan
i
s
alpha
Centauri
beta
Centauri
alpha
Crucis
beta
Crucis
SCP +
0
1
23
2
3
1
2
2
2
3
2
1
4
2
0
5
1
9
6
1
8
7
17
8
1
6
9
1
5
10
14
Pointer
R.A. Setting Circle
R.A. lock knob
EQ1
U
sing the setting cir
cles
The quickest way to find objects is to learn the
Constellations and use the Red Dot Finder, but if the
object is too faint you may want to use setting circles on
your mount. Setting circles enable you to locate
celestial objects whose celestial co-ordinates have
been determined from star charts.
Your telescope must be polar aligned and the R.A. setting
circle must be calibrated before using the setting circles.
The DEC. setting circle was set at the factory, and does
not require calibrating the same manner as the R.A.
setting circle.
Reading the R.A. setting circle
The telescope's R.A. setting circle is scaled in hours,
from 1 through 24, with small lines in between
representing 10 minute increments. The upper set of
numbers apply to viewing in the Northern Hemisphere,
while the numbers below them apply to viewing in the
Southern Hemisphere (Fig.k).
Setting (calibrating) the R.A. setting circle
In order to set your Right Ascension circle you must first
find a star in your field of view with known coordinates. A
good one would be the 0.0 magnitude star Vega in the
Constellation Lyra. From a star chart we know the R.A.
coordinate of Vega is 18h 36m. Loosen the R.A. and
DEC. lock knobs on the mount and adjust the telescope
so that Vega is centred in the field of view of the
eyepiece. Tighten the R.A. and DEC. lock knobs to lock
the mount in place. Now rotate the R.A. setting circle until
it reads 18h36m. You are now ready to use the setting
circles to find objects in the sky.
Trac
king Celestial Objects
When observing through a telescope, astronomical objects appear to move slowly through the telescope's field
of view. When the mount is correctly polar aligned, you only need to turn the R.A. slow-motion to follow or track
objects as they move through the field. The DEC. slow-motion control is not needed for tracking. A R.A. motor
drive can be added to automatically track celestial objects by counteracting the rotation of the Earth. The
rotation speed of the R.A. drive matches the Earth's rotation rate for stars to appear stationary in the telescope
eyepiece. Different tracking speeds are also available in some models. A second drive can be added to give
DEC control which is very useful for doing astrophotography.
Fig.k
Pointer
R.A. Setting Circle
R.A. lock knob
EQ2
1
7
7
1
6
8
1
5
9
1
4
1
0
13
1
1
18
6
1
9
5
2
0
4
2
1
3
2
2
2
23
1
0
To Next Page
Loading...
Need help?
General
