User's Manual

AutoStar #497 HANDBOX
Observing
24
The Global Positioning System
The Global Positioning System (GPS) is comprised of 24
satellites orbiting the Earth that are constantly transmit-
ting their precise position and time. The system provides
highly accurate, worldwide positioning and navigation
information for any number of applications.
GPS receivers on the Earth acquire signals from three to
twelve satellites to determine the precise latitude, longi-
tude, and time of the receiver. (Accuracy of the receiver’s
position may be within 10 to 15 feet.) As AutoStar II uses
latitude, longitude, and time information to calculate the
positions of celestial objects, GPS is an important tool for
aligning your LX600 ACF telescope.
Detecting True Level
To detect level of the base of the telescope, AutoStar II
must calculate the tip and tilt of the telescope at three
compass points and then compensate for it. Finding level
involves the geometric calculations of a “plane”. In order
to defi ne a plane, three positions are necessary. This is
not unlike building a table: For a table to stand level and
solid, it must have a minimum of three legs. AutoStar II
makes gravitational measurements to make a precise
determination of true level.
Finding True North
Locating True North is one of the most important ingre-
dients in the alignment of a telescope. True North is the
axis—the pole—which the Earth spins about and is a
key reference for the motion of the Earth.
As you look at the night sky, the stars seem to move; in
fact, if you watched long enough or took a long time-
exposure photograph, you’d realize that the stars seem to
revolve around one point—the pole or True North. When
AutoStar II knows where True North is and also knows the
time, it can calculate the location of all the other objects
in the sky.
One traditional way to fi nd True North is to locate the
North Star, Polaris, which lies very close to True North.
Another way to calculate True North is to use gyroscopes
or accelerometers.
The LX600 ACF determines True North by using a mag-
netic North sensor. The sensor locates magnetic North.
Magnetic North is not True North, but a measurement of
the magnetic lines of the Earth. Magnetic North may
deviate several degrees from True North. But AutoStar
II, using the observation site location determined by the
GPS and magnetic North information, can calculate the
position of True North.
Some areas are subject to magnetic disturbances, and
the magnetic fi eld of the Earth changes slightly from year
to year. AutoStar II allows you to adjust for discrepancies
in the local magnetic fi eld using the “Calibrate Sensors”
option in the Telescope menu. See page 33 for more
information.
Calibrate Home
After a precise polar alignment (drift alignment) you may want to
calibrate the Home Sensors on your mount. This procedure sets
the 90 degree declination position and the zero hour angle of the
RA axis very accurately. When you perform future alignments,
the system uses these positions to aid in a precise alignment.
Parking the Scope
Designed for a telescope that is not moved between observing
sessions. Align the telescope one time, then use this function to
park the telescope. Once parked, the screen prompts to turn off
power.
The advantage of parking is that you do not need to align the
telescope the next time you turn on Autostar; it remembers your
alignment. Tip: When waking their telescope, some users select
a bright star from the Objects menu and perform a GoTo on that
star. If the star is not in the exact center of the eyepiece, move
the star to the center using the arrow keys and then hold ENTER
down for more than two seconds. This activates the Enter to Sync
function and fi ne tunes and improves the telescope’s alignment.
Important Note: When the “Park Scope” option
is chosen and the display prompts you to turn off
the telescope’s power, Autostar II is unable to be
returned to operation without turning the power
off and then back on.
Most users can use the default park position when parking
their LX600. The default park position is identical to the home
position; fork arms parallel to the ground plane and OTA pointing
forward toward the celestial pole.
However, if you are storing your telescope in a location where it
cannot be stored in the home position, for example, such as an
observatory with a top that slides back, just move your telescope
to the position you want to store it. Choose “Park Position” from
the Setup: Telescope menu. When “Park Position” displays,
use the down arrow key to scroll through the choices. Select
“Use Current” if your position is anything other than the Home
Position. If you are using the Home Position, select “Use Default.”
StarLock Operation
Your LX600 Telescope incorporates the advanced StarLock™
system that makes target acquisition and accurate autoguiding
during exposures completely automatic. The StarLock system
incorporates a narrow fi eld 80mm f/5 optic and a super wide-
angle lens that automatically fi nds your target with high precision,
locks on to a fi eld star and automatically begins guiding.
StarLock Menu: