Locating The Celestial Pole; Precise Polar Alignment - Meade LX80 Instruction Manual

Locating the Celestial Pole

To get basic bearings at an observing location, take
note of where the Sun rises (East) and sets (West) each
day. After the site is dark, face North by pointing your
left shoulder toward where the Sun sets. To precisely
point at the pole, fi nd the North Star (Polaris) by using
the Big Dipper as a guide (Fig. 47).
For precise tracking of astronomical objects, your
telescope should be Polar aligned.
Important Note: For almost all astronomical observing
requirements, approximate settings of the telescope's
latitude and polar axis are acceptable. Do not allow
undue attention to precise Polar Alignment of the
telescope to interfere with your basic enjoyment of the
instrument.
AudioStar Polar Alignment
AudioStar provides four different methods for Polar
Alignment: Easy, One-Star, Two-Star and Three Star.
Little Dipper
Big Dipper
Figure 47: Locating Polaris
Easy Polar Alignment
Two alignment stars are chosen by AudioStar based
on the date, time and location entered. First, choose
"LX80 Polar" from the "Setup: Telescope: Telescope
Model" menu and place the telescope into the Polar
Home Position as described on Page 28. The rest of
the procedure is identical to the (alt/az) "Two-Star".
One-Star Polar Alignment
Polar One-Star Alignment requires some knowledge
of the night sky. AudioStar provides a database of
bright stars and one star from this database is chosen
by the observer for alignment. Polaris is chosen by
AudioStar. First, choose "LX80 Polar" from the "Setup:
Telescope: Telescope Model" menu and place the
telescope into the Polar Home Position as described
on Page 28. The rest of the procedure is almost
identical to the (alt/az) One Star alt/az Alignment,
except that AudioStar prompts you to point the
telescope at
telescope eyepiece.
62
Polaris
Cassiopeia
Polaris and center it
Two-Star Polar Alignment
Polar Two-Star Alignment requires some knowledge of
the night sky. AudioStar provides a database of bright
stars and two stars from this database are chosen by
the observer for alignment. First, choose "LX80 Polar"
from the "Setup: Telescope: Telescope Model" menu
and place the telescope into the Polar Home Position
as described on Page 28. The rest of the procedure
is almost identical to the (alt/az) Two Star alt/az
Alignment, Page 49.

Precise Polar Alignment

It should be emphasized that while doing casual
observing, precise alignment of the telescope's polar
axis to the celestial pole is not necessary. Don't allow
a time-consuming effort at lining up with the pole to
interfere with your basic enjoyment of the telescope.
For long-exposure photography, however, the ground
rules are quite different, and precise polar alignment is
not only advisable, but almost essential.
Even though the LX80 telescopes offers a sophisticated
drive system, the fewer tracking corrections required
during the course of a long-exposure photograph,
the better. In particular, the number of declination
corrections required is a direct function of the precision of
polar alignment.
Precise polar alignment requires the use of a crosshair
eyepiece. The Meade Illuminated Reticle Eyepiece
(see Optional Accessories, Page 52) is well-suited in
this application, but it is also preferable to increase the
effective magnifi cation through the use of a 2x or 3x
Barlow lens as well. Follow this procedure (particularly
if the pole star is not visible), sometimes better known
as the "Drift" method:
1. Obtain a rough polar alignment as described earlier.
Place the illuminated reticle eyepiece (or eyepiece/
Barlow combination) into the accessory adapter of
the telescope.
2. Point the telescope, with the motor drive 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 RA of the meridian and within ±5° of the
celestial equator (see Celestial Coordinates, Page
61). Pointing the telescope at a star that is straight
in the
up, with the declination set to 0°, will point the
telescope in the right direction.