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38 • Using the Drive
This function allows you to select the speed at which the motor moves when
corrections are made via the hand controller. Once the drive is activated, the
default setting is .3 times sidereal rate. Press the Speed button to change the
guiding rate. The selections are .3x, .5x, 8x, and 16x sidereal rate.
For guiding, use either the .3x or .5x setting. These two rates allow optimal
use with autoguiders. The faster settings — 8x and 16x — are perfect for
positioning objects within the field of view.
The telescope can also move at 20x speed WITHOUT changing any of the
guide settings. To control the telecope at 20x speed, press the button that
corresponds to the direction you want to move the telescope. While holding
the button down, press the opposite directional button. For example, if you
want to move the telescope west, hold the west button down and then press
the east button. Conversely, if you want to move the telescope east, hold the
east button down and then press the west button. This “fast-set” function also
works in declination. It should be noted that the R.A. setting circle does not
remain calibrated when using any of the slewing rates.
NOTE: If the 20x speed is not functioning (but all other speeds do), it is
probably due to low voltage from your power source.
The drive has four basic rates: sidereal, solar, lunar and King (which is a
modified sidereal rate that takes into account atmospheric refraction). While
solar and lunar rates are obvious, sidereal and King rates require a little more
explaining. Sidereal rate is based on a single rotation of the Earth which takes
1,436.5 minutes. An astronomer by the name of King discovered that atmo-
spheric refraction affects the apparent motion of objects across the sky. The
King rate takes into account this refraction caused by the Earth’s atmosphere
and is recommended for deep-sky astrophotography. For deep-sky observing,
either King or sidereal rate is fine.
Each of the tracking rates is represented by an icon. Sidereal rate is repre-
sented by a star ( ), solar rate by a sun (
), lunar rate by a crescent moon
( ) and King rate by a crown ( ) . Next to each icon is an LED to indicate
which rate has been selected. Once the power has been turned on, the drive
tracks at sidereal rate, the default tracking rate. To change the tracking rate,
press the “TRACK RATE” button. Pressing the button once changes the drive
rate once. The rates are selected sequentially from bottom-to-top as listed
above.
Note that the PEC function does NOT have to be activated for the drive to work.
However, once PEC is activated, the drive rate is locked on the one selected.
You can not change rates until PEC is turned off.
Guide Speed
Figure 5-3
Tracking Rate Selection
Figure 5-2