celestron 127 slt gear backlash in left right slew.

[fluffybunnykiller]

hi folks , got this scope last week and since have played with it on the odd moment of clear sky, the one thing that springs to mind is that if i say slew the scope left to right to change the view , then slew right to left there is a very pronounced pause between the cope moveing in the opposit direction.

it is almost as if there are teeth missing from the drive, i know this isnt the case as it will slew a full 360 deg with out stoping on any missed teth. the same for going in the reverse direction. there will be some slop in the gear train but this seems to be rather more than i would accept to ok.

any ideas?

[Baffa]

I have that backlash in my 127 SLT aswell, I don't know if there is an easy way of fixing this. But knowing this problem I made sure I always ended my alignment with the "right" button so the gotos wont be messed up.

Is the movement also jerky and sometimes just slowes down considerably when doing a 360 deg turn? Mine was acting like this before the alt/az motor died.

[tjr]

I *think* there is a setting to remove backlash in these mounts. It effectively allows the mount only to rotate clockwise, eliminating the 'pause' when changing direction. Fine if you can live with the added time it takes the scope to rotate say 350^o rather that -10^o...

[fluffybunnykiller]

there is a setting in the system, to only a left or right slew but i have still to figure this out as to be honest the manual is pretty Rubbish.

my problem with the gears is in both directions, i go left its ok but try to go right then there is a long pause with the motors running before it starts to move right, and exactly the same thing but if i starter it moveing right then change to move it left i get the same thing, the single direction would be a great help if a little slower but not a problem.

i have since bought a 12v 10ah mini battery about 9inch by 3inch that will sit nicely on the center brace to give some added weight to help kill the shimmers. but what do i set the power plug to ? is it center positive or outer positive?

[Donkeiller]

there is a setting in the system, to only a left or right slew but i have still to figure this out as to be honest the manual is pretty Rubbish.

my problem with the gears is in both directions, i go left its ok but try to go right then there is a long pause with the motors running before it starts to move right, and exactly the same thing but if i starter it moveing right then change to move it left i get the same thing, the single direction would be a great help if a little slower but not a problem.

i have since bought a 12v 10ah mini battery about 9inch by 3inch that will sit nicely on the center brace to give some added weight to help kill the shimmers. but what do i set the power plug to ? is it center positive or outer positive?

Centre positive

[fluffybunnykiller]

thanks for the info

[Stargazer51N]

Hi, I have this mount and find that there is quite a pause when moving from one direction to another particularly on slower slew speeds. There is a backlash compensation figure you can change in the setup menu which spins the motor in the opposite direction for a few moments after you've driven the scope to an object. This means that the backlash doesn't affect the tracking and it doesn't matter which direction you slew to an object (although during the alignment at the start of a session I always finish my moves with down and right actions). Here's an excerpt from the manual ...

Anti-backlash – 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 eliminate 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. Positive backlash compensation is applied when the mount changes its direction of movement from backwards to forwards. Similarly, negative backlash compensation is applied when the mount changes its direction of movement from forwards to backwards. When tracking is enabled, the mount will be moving in one or both axes in either the positive or negative direction, so backlash compensation will always be applied when a direction button is released and the direction moved is opposite to the direction of travel.

To set the anti-backlash value, scroll down to the anti-backlash option and press ENTER. Enter a value from 0-100 for both azimuth and altitude directions 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.