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2. Telescope Position.
The first display shows the RA and
DEC (telescope position in stellar coordinates) and the
second display (accessed by pressing the ENTER key)
shows the telescope position in ALTAZ coordinates.
3. Time and Date.
The first display shows local and Sidereal
time and the second display (accessed by pressing the
ENTER key) shows the date.
4. Timer and Freq.
This display is a countdown timer and
allows the user to change drive rates. These are advanced
features.
5. All
Off.
This mode simply turns off all displays and
backlighting. You can also adjust the backlighting
brightness by pressing the ENTER key and using the
PREV
and NEXT keys to adjust the brightness.
f. Library Object Keys
While in any of the 5 main keypad display modes, you can directly
access the library objects by using the M, STAR, or
CNGC keys
(see APPENDIX C, page 31, of this manual for more
information on
the 64,359 Object Library). Simply press an object key, and type
in the number of the object desired, followed by ENTER. For
example, a good first object for the first part of the year is M42 —
the Great Orion Nebula.
Press the M key, the 4 key, the 2 key, and finally the ENTER key.
The display will show data on the object (name, rating, object
type, brightness, size). Now press GO TO. The telescope will
automatically slew to M42.
If the object entered is not above the horizon, the keypad hand
controller will display the message "Object Below Horizon."
Other good first objects (if above the horizon) are any of the M
objects — from M1 to M 110, and the planets. To find a planet
enter: (NOTE: 903 is the Moon.)
OBJECT LIBRARY PLANET LEGEND
PLANET
STAR #
PLANET STAR #
MERCURY
901
SATURN
906
VENUS
902
URANUS
907
MARS
904
NEPTUNE
908
JUPITER
905
PLUTO
909
3. Follow the keypad display prompts to choose and center
the
the second alignment star. Be sure to use the keypad to slew
to the second star. After pressing the ENTER key
in the last
step, the keypad display should show the
TELESCOPE/OBJECT LIBRARY screen.
Important Note: Whenever using either of the 2-Star
alignment procedures (at a known SITE or at an unknown
SITE), choosing the proper two stars will determine the pointing
accuracy of the telescope. Choose two stars that are not too
close together — try to use stars that are at least 90° apart. Do
not use Polaris because RA changes very fast at the Pole and
minor centering errors translate to large RA pointing errors.
Also, avoid stars near the zenith (straight up) since azimuth
changes very fast in this area. Generally speaking, choosing
two stars as far apart as possible will yield very accurate
pointing, often within a few arc minutes.
The LX200 calculates the distance between the two stars that you
chose in the alignment steps and compares this to the distance
that you actually slewed the telescope. This is a check
to be sure
you centered the correct stars during the alignment
steps. Should
the LX200 discover a discrepancy, the keypad will display an
"Align Mismatch — Check Stars" message. If you get this
message after aligning the telescope, check that
you are using the
correct stars and align again.
c. Unknown SITE
To use the LX200 telescope at an unknown location, use the
following procedure:
1. Select site #5 (UNKNOWN) from the SITE menu.
NOTE: This site cannot be edited like site numbers 1 to 4 as
described in Entering Basic Information, page 10.
2. Follow the keypad display prompts to select and center
the
two alignment stars.
As described above, the LX200 will check the accuracy of the
two stars and give the "Align Mismatch — Check Stars"
message if it detects an error.
d. Which Alignment Method to Use?
Each of the three method described above has advantages and
disadvantages. The following table summarizes these
properties.
4. Star Alignment
The 2-Star initialization routines provide three options for aligning
the LX200 telescope when in the ALTAZ mode.
NOTE: The 2-Star initialization routines only apply to the ALTAZ
alignment mode (see MODE FUNCTIONS, page 16, for POLAR
and LAND mode initialization).
The first and second options require that entry of the SITE and
TIME information as described in
Entering Basic Information
(page 10). The third option is used when the SITE information
is
not known or has not been entered into the LX200's memory.
a. 1-Star with Known SITE
The 1-Star alignment routine was explained in detail in
Setting Up
the Telescope
(page 11).
b. 2-Star at Known SITE
To use the 2-Star alignment procedure at a known site, follow
these steps:
1. Select the 2-Star alignment (by pressing the "2" key); the
keypad display will prompt you to level the base. This
leveling step requires a rough level only and, unlike the 1-
Star alignment routine, does not affect the pointing accuracy
of the telescope. (See Section d. below for a summary of the
differences in telescope operation when selecting each of
the three alignment procedures.)
2. After leveling the base and pressing ENTER, follow the
keypad display prompts to select the first alignment star.
Slew to that star using the N, S, E, and W keys.
1-Star
Known 2-Star Known 2-Star
Unknown
Pointing
Accuracy
Determined By:
Level of
Telescope
2-Star
Alignment
2-Star
Alignment
Atmospheric
Refraction
Correction*
Yes Yes No
Atmospheric
Refraction
Correction
Determined By:
Level of
Telescope
Level
of Telescope
Not
Applicable
When
Best
Used
Best used
when the
telescope is
permanently
mounted and
accurately
leveled
Best used on a
transportable
telescope
with
the SITE
information
available
Best used
when the
SITE
information
is
not
available
* Atmospheric Refraction Correction: Light from an astronomical
object
is "bent," (refracted) as it passes through the atmosphere. This bending is
more pronounced near the horizon because there is more atmosphere for
the light to pass through, and it shifts the apparent position of the star. The
LX200 calculates this bending and compensates for it when slewing to
objects near the horizon.
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