Lining Up With The Celestial Pole - Meade 8" LX100 Series Instruction Manual

-35-
6.
Lining
Up
With The Celestial Pole
Objeas in the sky
appear to revolve
around
the
celestial
pole.
(Actually, celestial objects are
essentially
"fixed," and their apparent
motion is caused by the Earth's a<ialrotation). During
any
24 hour period, stars
make one
complete
revolution about the pole, describing concentric circles with the pole at the
center.
By
lining
up the
telescope's polar
a<is
with the North Celestial
Pole (or for observers located in Earth's Southern
Hemisphere with the South Celestial Pole) astronomical objects may be followed, or tracked, simply
by
moving
the telescope about one axis, the
polar a:ris.
ln the
case
of
the Meade
8'and
10'Schmidt-Cassegrain
telescopes, this
tracking
may be accomplished automatically with the electric motor drive.
lf
the telescope
is
reasonably well
aligned
with the pole, therefore, very
little use
of the
telescope's Declination
slow motion control is necessary
-
virtually
all
of the required telescope trac*ing will
be in Right Ascension.
(lf
the telescope were perfectly aligned with the
pole, Ile
Declination tracking of stellar
objects
would
be
required).
For
the purposes
of
casualvisual telescopic observations, lining
up
the telescope's polar axis to
within
a
degree
or
two
of the
pole
is more than
sufficient:
with this level
of
pointing accuracy,
the
telescope's
motor drive will track accurately and
keep objects in the
telescopic field
of view
for perhaps
20 to
30 minutes.
Begin polar aligning the telescope
as
soon as you can see
Polaris. Finding Polaris
is simple. Most
people
recognize
the "Big Dipper.'The Big Dipper
has two stars that
point
the
way to Polaris (see Fig. 22). Once Polaris
is
found,
it is
a
straightfonarard
procedure
to
obtain
a
rough
polar
alignment.
To line up the
8'or
10" LX100 with the Pole, follow
this
procedure:
1
.
Using the bubble level located
on the floor of the wedge,
adjust
the
tripod legs
so that the telescope/wedge/tripod
system reads'level."
q.
F-
t
,e
:.- -..
'
Little
o'o2"'
Polaris
't
.'.
-/
'
.'r/
,'' '
aig
olpper
n
'
Cassiopeia
Fig.
22:
Finding Polaris
2. Set the EquatorialWedge to your observing latitude as described in Section
3.
3.
Loosen
the Dec. lock (#2,
Fig. 8), and rotate
the telescope tube in Declination so that the
telescope's
Declination reads
90'.
Tighten the Dec.
lock.
4. Using the Azimuth and Latitude controls
on
the Wedge, center Polaris
in
the field
of
view.
Do not use the
telescope's Declination or Right Ascension controls during this process.
At
this point,
your
polar alignment
is
good enough
for casual observations. There
are
times,
however, when
you will
need
to have
precise polar alignment, such as when making fine astrophotographs or
when
using
the setting circles to
find
new objects.
As an aside procedure, during your first
use of
the telescope, you should check the calibration
of the
Declination setting circles (see #3, Fig. 8), located at the top of each fork
arm.
After performing the
polar alignment procedure, center the
star Polaris in the telescope
field.
Loosen slightly the knurled
central hub of each Declination setting
circle.
Now turn each circle until
it
reads 89.2', the Declination
of Polaris, and then tighten down the knurled knobs, avoiding any motion
of the circles.