USE
OF
THE TELESCOPE
IN
EQUATORIAL
POSITION
BALANCE
Both the telescope tube and the counterpoise, or
balance weight, must be
carefully
balanced
during
every operation.
EQUATORI~L
ADJUSTMENTS
By
means
of
the built-in spirit level, determine
that the
top
of
the stand
is
level when set up
for
observing (Figure 4.)
To
save setup time, it
is
suggested
that
three stone
or
concrete blocks
with gunmetal or brass plugs inserted in them
be placed in a
triangle
so
as to accommodate
each
tripod
leg. The metal spikes
on
the
tripod
legs can be inserted into the plugs, thus assuring
corr-ect placement
of
the telescope each time.
Set
the telescope tube as nearly
parallel
to
the
polar
axis
as
possible. Next,
set
the
polar
axis
reasonably correct in azimuth
by
means
of
the
azimuth circle on the
tripod
base
and
a compass,
making
allowance
for compass
deviation
at
the
point
of observation. Adjust the
altitude
of
the
polar
axis to the
proper
angle
to
equal the
latitude
of
the place
of
observation.
As
a rule,
it
is
easier to
set
the
polar
axis
at
the correct
altitude
than it
is
to set it
at
the -meridian.
Direct the
polar
axis
toward
the true north pole
which lies
about
one degree (two
full
moon
breadths) distant from Polaris
and
on a line be-
tween Polaris and
Alkaid
(7]
Ursae Majoris), the
latter being the last star in the tail
of
the
Great
Bear or Big Dipper. For best results, choose a
time for observing Polaris
as
it transits above or
.-
below
the pole Center Potaris in the field
of
view
of
the telescope; then raise or lower the
polar
axis, not over one degree,
by
means
of
the
Inclination and azimuth adjustments. This should
establish the
polar
axis
accurately
enough to
enable
locating an obiect in the field
of
view
of
the finder telescope.
Assuming that the
altitude
of
the
polar
axis
is
apprOXimately correct, here
is
a simple rule
to
refi
ne
the setting:
Center a star in the field
of
view
of
a moderately
high powered eyepiece.
If.
the
polar
axis
is
not
In
the meridian, it
will
be necessary
to
move the
declination and hour
angle
settings
to
keep the
star centered If the correct:on in declination was
Figure 4
toward
the
North
in the northern hemisphere
or
toward
the South in the southern hemisphere, the
upper end
of
the
polar
axis
is
pointing too
far
westward. If the correction
is
in an opposite
direction
to
that described, the
polar
axis
is
point-
ing too
far
eastward. Shift the
polar
axis in
azimuth'
in the direction indicated
and
make a
fresh trial.
One
or
two
such
trials should put the
polar
axis in sufficiently close adiustment
for
most practical purposes.
Use
two
ar
three stars
in Widely separated parts
of
the sky
for
each trial
Because
of
its
rapid
motion in declination,
the
.moon does not make a practical check point.
When
the declination
and
the hour
angle
have
been
properly
adiusted, the obiect
will
be near
the
middle
of
the field
of
view The finder teles-
cope
is
an
aid at this point
by
showing on a small
scale the
configuration
of the stars involved.
In
the main telescope, it
is
preferable
to
use
a
low
power
eyepiece to locate the desired image.
In
the case
of
an asteroid,
faint
satellite,
or
other
object producing a star-like image, it may be
necessary
to
plot
a position on a star chart to
distinguish this image from a star
Once on
obiect
is
in the center
of
the field
of
view, it
will
stay there since the telescope
is
now
following
the stars in their diurnal motion.
USE
OF
THE TELESCOPE IN
TERRESTRIAL
POSITION
To
observe terrestrial objects, place the telescope
in the position shown (Figure 6).
To
produce
images having minimum distortion and which
are
right
side up,
use
the erecting prism and a
low
power eyepiece.
5
