Precise Polar Alignment - Meade LX200 Instruction Manual

d. The telescope slews to Polaris' position. Using the azimuth
and latitude controls on the permanent pier, center Polaris
in the field of view. Do not use the telescope's Dec. or
R . A . c o n t rols during this step. Press E N T E R w h e n
Polaris is centered in the eyepiece.
e. The telescope slews to a second alignment star. It prompts
you to center this star in the eyepiece. Use the telescope
controls to center this star. Press ENTER.
At this point, your polar alignment is sufficient to begin the

precise polar alignment.

Precise Polar Alignment
The fewer tracking corrections required during a long-exposure
photograph, the better. (For our purposes, long-exposure
means any photograph requiring 10 minutes or more). In
particular, the number of Dec. corrections required depends on
the precision of polar alignment.
Precise polar alignment requires a crosshair eyepiece. The
Meade illuminated-reticle eyepiece is well suited in this
application, but you will want to increase the eff e c t i v e
magnification with a 2x or 3x Barlow lens. Use the following drift
method:
a. Obtain a rough polar alignment as described earlier. Place
the illuminated-reticle eyepiece (or eyepiece/Barlow
combination) into the eyepiece holder of the telescope.
b. Point the telescope, with the drive motor running, at a
moderately bright star near where the meridian (the North-
South line passing through your local zenith) and the
celestial equator intersect. For best results, the star should
be located within ± 30 minutes in R.A. of the meridian and
within ± 5° of the celestial equator. (Pointing the telescope at
a star that is straight up, with the Dec. set to 0°, will point the
telescope in the right direction.)
c. Note the extent of the star's drift in Dec. (disregard drift in
R.A.):
If the star drifts South (or down), the telescope's polar axis
is pointing too far East (Fig. 11).
Polaris
Fig. 11: Mount too far
East.
If the star drifts North (or up), the telescope's polar axis is
pointing too far West (12).
d. Move the pier in azimuth (horizontally) to change the polar
alignment. Reposition the telescope's East-West polar axis
orientation until the start stops drifting North-South. Track
the star for long enough to be certain that its Dec. drift has
ceased.
NOTE:Figs. 11, 12, 13, and 14 show the telescope pointed
in the 90° position;not the 0° position that is required for drift
method alignment.This is done to illustrate the position of
the Pole Star relative to the polar axis of the telescope.
Polaris
Fig.12: Mount too far West.
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Polaris
Fig.13: Mount too low.
Polaris
Fig.14: Mount too high.
e. Point the telescope at another moderately bright star near
the Eastern horizon, but still near the celestial equator. For
best results, the star should be about 20° or 30° above the
Eastern horizon and within ± 5° of the celestial equator.
f. Again note the extent of the star's drift in Dec.
If the star drifts South (or down), the telescope's polar axis
is pointing too low (Fig. 13).
If the star drifts North (or up), the telescope's polar axis is
pointing too high (Fig. 14).
g. Change your pier's latitude angle, based on your
observations above. Track the star again long enough to be
certain that Dec. drift has ceased.
The above procedure gives very accurate polar alignment. It
minimizes the need
astrophotography.
As an aside procedure, during your first use of the
telescope, check the calibration of the Dec. setting circle
(3, Fig. 1), located at the top of each side of the fork. After
performing the polar alignment procedure, center the star
Polaris in the telescope field. Remove the knurled central
hub of the Dec. setting circle and slightly loosen the two
bolts located under the knob. Turn the circle unit until it
reads 89.2°, the Dec. of Polaris, and then tighten down
the two bolts and replace the knurled knob. Should you
wish to use the manual setting circles, the R.A. setting
circle (9, Fig. 1) must be calibrated on the R.A. of a star
(see APPENDIX B) manually every time the telescope is
set up. The R.A. setting circle has two sets of numbers:
the inner set is for Southern hemisphere use and the
other is for Northern hemisphere use.
for tracking corrections during