Leisure Time LX20 instruction manual Backlash

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9.HI-PRECISION:The High-Precision Pointing feature of LX200 allows for very precise pointing of the telescope. By incorporating the unique LX200 SYNC command, 0.3 arc- sec resolution encoders, and high-speed DC servo motors, observers can now place objects in the telescope's field of view with 1 arc-minute or better pointing accuracy. This makes critical image placement applications, such as CCD imaging, possible.

Normal telescope pointing accuracy is better than 5 arc- minutes when doing a casual alignment, which is more than accurate enough for most observing applications. (A "casual" alignment is one that uses the UNKNOWN SITE or one that is done without the use of a reticle eyepiece to exactly center the alignment stars.) This type of alignment will put objects into the field of view of most eyepieces and is more than adequate for almost any visual observing application.

A "critical" alignment will improve the pointing accuracy of the telescope to 2 arc-minutes or better. This type of alignment requires accurate SITE information, time, date, proper selection of the two alignment stars, and a reticle eyepiece to exactly center the alignment stars. These steps generally require only a few extra seconds to accomplish, and will improve the telescope's positioning by a substantial amount. Using the "critical" alignment will provide telescope positioning suitable for all but the most demanding pointing applications — including CCD imaging with larger chip cameras, like the Meade Pictor 416 and Pictor 1616 CCD cameras.

The HI-PRECISION feature increases the pointing accuracy of the LX200 to 1 arc-minute or better and also requires the "critical" alignment described above. This will yield the best pointing accuracy possible, placing objects onto the active area of the even the smallest CCD cameras available.

It should be stressed that for most applications, using the HP feature is NOT required to get maximum enjoyment out of the telescope. For an evening of simple visual observations, the "casual" alignment is all that is required. Don't let the pointing precision of the telescope become more important than the fun of observing the night sky!

The High-Precision Pointing mode requires the "critical" alignment, described above, to maximize the telescope's pointing ability. The LX200 default condition is with HP disabled. To activate the HP mode, select the "hi-precision" option from the TELESCOPE menu (option #9). When selected, "HI-PRECISION" will change to upper case letters.

When HP is active, the LX200 automatically does several things whenever a GO TO is initiated.

a.HP will search the alignment star database and find the three closest stars to the object (or position) entered. This process takes about 10 seconds and the keypad will show Display 26:

b.The telescope will slew to the nearest alignment star. These are all bright (brighter than 3rd magnitude) stars and far enough apart to insure that there will only be one in the field of view. The keypad display will show Display 27:

using a reticle eyepiece, center tne star in tne neia or view. (Or center the star on the CCD chip if using a CCD camera.) Press GO TO when the star is centered.

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.

c.The telescope will slew to the selected object or position.

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:

a.Press the MODE key on the keypad until the TELESCOPE/OBJECT LIBRARY menu appears. The cursor should be next to the TELESCOPE option — if not, press the PREV key to move the cursor up one space.

b.Press ENTER to select the TELESCOPE functions.

c.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 4 is displayed. This represents the current slew rate in degrees per second.

d.Press the ENTER key to change the slew rate. Each successive ENTER key press increments the slew rate by 1 degree per second.

e.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 4 degrees per second.

11.BACKLASH: The Backlash feature is only available in the POLAR mode.

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 is reversed.

To program the Dec. backlash, use this procedure:

a.Move to option #11 from the TELESCOPE menu. The keypad display will show:

'"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).

b.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.

c.The GUIDE speed for the Declination motor is 15 arc- seconds per second. Therefore, multiply the number of seconds delay by 15.

d.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