Are my star trails the result of worn worm gears?

[oldannie]

My NEQ6 is now some six years old and whenever I image a target high in the sky, when near the zenith, 2 or 3 images are spoilt because of star trailing.  Over the duration of these 2/3 images often  10/15 mins exps everything goes back to normal but it's become a waste of time imaging targets high in the sky.  My setup is Takahashi 106, Atik mono 460 plus filter wheel and stand alone guider, MGEN 11. Observatory based.   I have assumed it's a bad case of backlash and the worm gears showing their age but not at all sure?

Annie

 

 

[newbie alert]

Is it belt driven?

[1parsec]

18 hours ago, oldannie said:

My NEQ6 is now some six years old and whenever I image a target high in the sky, when near the zenith, 2 or 3 images are spoilt because of star trailing.  
Annie

 

 

I'd guess it is backlash in the Dec axis worm wheel.    When you image away from the zenith you probably have a small imbalance that keeps the contact on one side of the gearing.
At the zenith  the mount is more likely to 'wander between the gap in the gears  causing the trailing because the scope is vertical.  
First thing to check / adjust is the Dec backlash.  A search for' backlash adjustment' should show a lot of links on how to do it.

ATB   Dave. 

[oldannie]

That makes sense Dave. Have already been looking at Astro Baby's videos about this and have an engineer friend who will help with this issue.  Thanks for the clear explanation.

Annie