Celestron Ultima 8 Instruction Manual page 41

LUNAR This rate is used for tracking the Moon.
PEC
This is only used on a telescope that is polar aligned on a wedge. Furthermore, you need to have the tracking rate set to
EQ NORTH or EQ SOUTH.
Periodic error correction, or PEC, is used for astrophotography or CCD work. PEC corrects for repeating errors caused
by the worm gear. The worm takes about 5.4 minutes to make one complete revolution. Any errors in the worm will
repeat every time the worm makes a revolution. These are called periodic errors. These errors can be corrected by using
the PEC TRAIN function.
Watch a star with an illuminated reticle eyepiece, like the Celestron Micro Guide Eyepiece. You will notice that the star
will slowly drift ahead or behind the illuminated crosshairs. Using the diamond buttons, set to PHOTO speed, practice
keeping the star centered. Set PEC to TRAIN. Keep the star centered using the diamond buttons. The PEC is
remembering the corrections you make. After 5.4 minutes, it will play back the corrections you made and still keep
recording any new corrections. When you feel it is tracking well, switch PEC to ON. Now, the PEC will play back the
corrections and will not record any new corrections you make. Any resulting tracking errors are random in nature and
must be corrected manually.
VOLTS
This is a built-in voltmeter to give you an idea of the status of your batteries. 8.5 volts is about the minimum the telescope
needs to run. The maximum voltage is about 18 Volts. Any higher voltage is not recommended and can significantly
shorten the life of the SLEW motors.
AZM GEAR
The Azimuth Gear Ratio: This allows you to change the relative speed of the tracking motors. This can be useful for
tracking comets or asteroids. The factory setting is 1.0000. The range of settings is from 0.0000 to 2.9999. When set to
0.0000, the motors will not drive at all, and when set to 2.9999, the motors will run almost 3 times faster. The relationship
of drive speed to this number is linear. 1.5000 will run the motors at 1.5X.
Here is how to change the gear ratio.
ACTION
Start at SETUP menu
press ENTER
press DOWN 5 times
press ENTER
press DOWN
press ENTER
press UP 5 times
press MENU
NOTES
If you want to do this under the sky you will be able to see the
effects in an eyepiece. Be sure tracking is ON and the
telescope is star aligned.
Enter into the list of SETUP items.
Scroll down to the AZM GEAR item
Enter into the AZM GEAR menu. The leading "1" will now
blink.
Changes the one to zero. The tracking rate is now zero.
Accept the entry of zero and move the cursor to the next
character.
Change tracking speed to 1/2 normal speed
Return to main menu. The new AZM GEAR ratio will remain
.5 even after cycling power.
DISPLAY
MENU
SETUP
SPEED
CENTER
AZM GEAR
1.0000
AZM GEAR
1.0000
AZM GEAR
O.0000
AZM GEAR
0.0000
AZM GEAR
0.5000
MENU
SETUP
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