Celestron CGEM DX Mount and Tripod Computerized Telescope CGEM DX Mount Manual - Page 16

OTA Orientation - Some users may wish to use an optional tandem bar adapter which allows you to attach to the mount two optical tubes at the same time. When most tandem bars are attached to a mount, the optical tubes are positioned at a 90 degree angle from the standard configuration. In order for the mount to be successfully aligned with the stars, it must know that a tandem bar is being used and in which direction the optical tube(s) are positioned (East or West) when beginning an alignment. The tandem option must be set before beginning any of the initial star alignments. To set this option, go to the Scope Setup menu and select the Tandem option and press ENTER. Then select from one of the following options: • East - If the attached optical tubes are facing towards the east when the declination index makers are align, select East. • West - If the attached optical tubes are facing towards the west when the declination index makers are align, select West. • Normal - If the tandem bar is no longer being used, select "normal" to turn off this feature. Meridian - This feature instructs the mount on how to respond when it is slewing to objects that are accessible from both sides of the Meridian. See figure 3-3 for a definition of "Meridian". The Meridian feature allows the telescope tube to remain on a desired side of the mount when slewing, and continue to track according to the RA slew limits the user has set. See RA Limits below. The Meridian feature allows for four choices: • Favor Current - Allows the mount to favor whatever side of the mount that it is currently on when slewing to objects close to the Meridian. For example, if you RA slew limits are set to allow the mount to track 10 degrees past the meridian, then the telescope will continue to stay on its current side of the Meridian when slewing to objects that are as far as 10 degrees beyond your Meridian. • Favor West - If the target object is accessible from both sides of the mount, selecting "Favor West" instructs the telescope to point to the object as if it were on the west side of the meridian. The optical tube will then be positioned on the east side of the mount and pointing west. • Favor East - If the target object is accessible from both sides of the mount, selecting "Favor East" instructs the telescope to point to the object as if it were on the east side of the meridian. The optical tube will then be positioned on the west side of the mount and pointing east. • Disable - This is the default setting, which instructs the mount to always swing around to the other side of the pier as required to view objects on the opposite side of the Meridian. However once at the desired object, the mount will continue to track past the Meridian according the RA slew limits that have been set. Mount Settings - Once the mount setting have been calibrated (see Utilities section below) the values are stored and displayed in the hand control. It is not recommended that the calibration values be changed, however each setting can be changed if necessary to improve the performance of the telescope. • Cone Value - This is the cone error value set when Utilities / Calibrate Mount / DEC Switch - Cone is carried out. • DEC Index - This is the declination index error value that is stored when calibration stars are added after your initial star alignment. • RA Index - This is the R.A. switch error value set when Utilities / Calibrate Mount / R.A. Switch is carried out. RA Limits - Sets the limits that the telescope can slew or track in Right Ascension (R.A.) before stopping. The slew limits are represented in degrees and by default set to 0º, being the position of the telescope when the counterweight bar is extended out horizontally. However, the slew limits can be customized depending on your needs. For example, if you are using CCD imaging equipment that has cables that are not long enough to move with the telescope as it slews across the sky, you can adjust the slew limit on the side of the mount that is restricted by the cables, and command the mount the stop slewing before it reaches this point. Or if you are taking an image of an object that has just crossed the Meridian, you can set the limit to allow the mount to continue tracking in the same direction past the Meridian without the need to "flip" the telescope around to the opposite side of the mount (see Meridian feature above). Using the first example above, the user could slew the telescope in R.A. (azimuth) until it reaches the point that the cables are extended to their maximum. Then by displaying the telescopes azimuth in this position (by looking at Get Axis Position under the Utilities menu) you can determine the telescopes azimuth at its most extended position. Enter this azimuth reading for either the maximum or minimum azimuth slew limit to ensure that the telescope will not slew beyond this point. The telescope slew limits can be set to automatically stop anywhere between 40º above level to 20º below level (see figure 3-4). To set the RA Slew limit select the following: • RA East Limit - Enter a number between +40º to -20º to define the slew limit when the tube is on the east side of the mount. • RA West Limit - Enter a number between +40º to -20º to define the slew limit when the tube is on the west side of the mount. • Disable Limits - This disables any pre-defined values that have been entered and allows the mount to track the maximum amount pass the Meridian (ie. -20º on both sides) Figure 3-4 Warning: In order for the telescope to be able to slew to a star from the direction that minimizes the amount of backlash in the gears, it may be necessary for the telescope to slew beyond the specified slew limit in order to approach the star from the correct direction. This can limit your ability to slew to an object by as much as 6º from the RA slew limit set in the hand control. If this proves to be a problem, the direction that the telescope 14