Celestron 8i User Manual

21

To replace the contents of any of the user defined objects, simply save a new object using one of the existing 
identification numbers; NexStar will replace the previous user defined object with the current one.  

 - Displays the right ascension and declination for the current position of the telescope. 

 - Allows you to input a specific R.A. and declination and slew to it. 

   

Allows the user to customize the NexStar display by 

changing time and location parameters (such as time zone and daylight savings). 

 – All mechanical gears have a certain amount of  backlash or play 

between the gears.  This play is evident by how long it takes for a star to move in the 
eyepiece when the hand control arrow buttons are pressed (especially when 
changing directions). The NexStar's anti-backlash features allows the user to 
compensate for backlash by inputting a value which quickly rewinds  the motors just 
enough to reduce the play between gears.  The amount of compensation needed 
depends on the slewing rate selected; the slower the slewing rate the longer it will 
take for the star to appear to move in the eyepiece. Therefore, the   anti-backlash 
compensation will have to be set higher.   You will need to experiment with different 
values; a value between 20 and 50 is usually best for most visual observing, 
whereas a higher value may be necessary for photographic guiding.  

To set the anti-backlash value, scroll down to the anti-backlash option and press 
ENTER.  Enter a value  from 0-99 for both azimuth and altitude and press ENTER 
after each one to save these values.  NexStar will remember these values and use 
them each time it is turned on until they are changed. 

  Sets the limits in altitude that the telescope can slew without 

displaying a warning message. By default the slew limits are set to 0º to 90º and will 
only display a warning message if an object is below the horizon.   However,  the 
slew limits can be customized depending on your needs.  For example, if you have 
certain photographic accessories attached to your telescope preventing it from 
pointing straight-up, you can set the maximum altitude limit to read 80º, thus 
preventing the telescope from pointing to any objects that are greater than 80º in 
altitude without warning.   

 – When an alignment is complete, the NexStar automatically knows 

which celestial objects are above the horizon.  As a result, when scrolling through 
the database lists (or selecting the Tour function), the NexStar hand control will 
display only those objects that are known to be above the horizon when you are 
observing.  You can customize the object database by selecting altitude limits that 
are appropriate for your location and situation.  For example, if you are observing 
from a mountainous location where the horizon is partially obscured, you can set 
your minimum altitude limit to read +20º.  This will make sure that the hand control 
only displays objects that are higher in altitude than 20º.  If you manually enter an 
object that is below the horizon using the numeric keypad, the hand control will 
display a warning message before slewing to the object. 

The direction a star moves in the eyepiece varies 

depending on the accessories being used.  This can create confusion when guiding 
on a star using an off-axis guider versus a straight through guide scope.  To compensate for this, the direction of