Note: If this star is not in the field of view or if it is obstructed by a land object, the other two stars are
available. Use the PREV and NEXT keys to cycle through the three closest stars.
4. The telescope will slew to the selected object or position.
[ toc ] 10) SLEW RATE
Option #10 in the TELESCOPE menu is for changing the slew rate of the LX200 telescope. Slowing down
the slew rate will result in less noise as the telescope moves and will also use a little less power. To
change the slew rate, follow these steps:
1. Press the MODE key on the Keypad until the TELESCOPE / OBJECT LIBRARY menu appears on the
display. The cursor should be next to the TELESCOPE option - if not, then press the PREV key to move
the cursor up one space.
2. Press ENTER to select the TELESCOPE functions.
3. Press the PREV or NEXT keys to move the cursor to option #10: SLEW RATE. On the right hand part of
the display, the number 8 is displayed (6 is displayed on Version 4.34 for 12" LX200 telescopes). This
represents the current slew rate in degrees per second.
4. Press the ENTER key to change the slew rate. Each successive ENTER key press increments the slew
rate by 1 degree per second.
5. After setting the desired rate, press the MODE key to return to the TELESCOPE / OBJECT LIBRARY
menu.
Note: The slew rate is NOT stored in permanent memory and needs to be reset each time the telescope is
powered up. The default slew rate is 8 degrees per second on Ver. 3.30 and 6 degrees per second on Ver.
4.34.
[ toc ] 11) DEC. BACKLASH COMPENSATION
When taking long exposure astrophotographs, it is necessary to "guide" the photograph to make sure the
telescope is tracking perfectly, otherwise stars will appear as ovals instead of pinpoints. This is done by
setting the LX200 Keypad to the GUIDE speed, monitoring the star location (e.g. with an off-axis guider),
and making small corrections to the telescope position by using the N, S, E, and W keys.
When making these corrections, the R.A. motor will speed up or slow down (by pressing the "E" and "W"
keys). The Declination motor, however, when activated (by pressing the "N" and "S" keys) will actually stop
and reverse direction. Because of backlash in the Declination motor gearbox, there will be a few seconds
delay before the telescope begins to move when reversing direction.
The Dec. backlash feature compensates for the Dec. motor gearbox backlash and provides instant
telescope movement when the motor direction is reversed. (Note: this feature is only available in the
POLAR mode.)To program the Dec. backlash, use the following procedure:
1. Move to option #11 from the TELESCOPE menu. The Keypad display will show:
"-p;>11) BACKLASH 00."
The "00" in the display shows the number of arc-seconds of backlash the LX200 is set to compensate for
(the default setting is 0 arc-seconds).
2. While observing a star at high power, time the Declination movement delay when reversing the motor
directions (by pressing the "N" and "S" keys). Typical values are 2 to 4 seconds.
3. The GUIDE speed for the Declination motor is 15 arc-seconds per second. Therefore, multiply the
number of seconds delay by 15.
4. Press and hold the ENTER key for 1 second. The Keypad will beep and a blinking cursor will appear on
the Keypad display. Enter the number determined in step 3, above. Press ENTER when the number is
entered.
5. Check the time delay as described in Step 2, above. If there is still a time delay, then increase the
compensation number. If there is a slight jump when reversing direction, then the number is too large.
When the compensation number is correct, the LX200 telescope will move almost instantly when reversing
the direction in Declination. This number is stored in permanent memory and should never need to be set
again.
