EQ5 Mount 'shaking'

Hi all, I'm posting this question on behalf of a friend of mine, He bought a second hand EQ5 motorised mount some months ago, and has a problem with the mount shaking each time the motor drive is turned on.

I first suggested adding some weight to balnace it better, but no luck. He described it to me as looking at saturn, which is 20 arcseconds in diameter, and watching the planet shake from side to side over about 2 arcseconds. This seems now to be a permanent problem with the drive.

He has checked the worm gearing itself, alignment etc. but there is nothing obvious as to what is going on Even at low power, any star will shake from side to side with the motor engaged, but when it's off, using the slow motion control, all things are smooth.

Has anybody seen this before.
Any help would be appreciated, Thanks,
Keith..

Hi Keith - I can't give a definitve answer, sorry. I'm not familiar with EQ mounts.

But, perhaps a few questions might help...

When you say using the 'slow motion control' all is well, is the motor not engaged and this is a hand-assisted movement? If that's the case, then its the motor or the gears/worm.

Also, is there only a dec motor or both dec and RA? If both, I'm assuming its the dec motor that's the problem.

Its unlikely to be balance - it sounds like periodic error. But are you sure its 2 arcseconds? I'd be pushed to measure that even with a CCD :shock:

I'd suggest taking the mount apart (at your friend's own risk!) and seeing if anything is even slightly mis-seated, warped, bent etc. A good clean if it needs it might further identify the problem.

By the way, I did have some issues with the AP mount a while back - but following the AP procedure, and making sure the gear/worm were mating correctly fixed that. Perhaps the worm and gear are slighly out of kilter with each other?

If, God forbid, something large, solid and metallic has been bent it might need a trip back to a dealer or manufacturer.

I know I'm not giving you any answers here but I hope this helps...

Cheers

Dave

When you say using the 'slow motion control' all is well, is the motor not engaged and this is a hand-assisted movement? If that's the case, then its the motor or the gears/worm.

Correct, the motor is not engaged. Itis the gears/worm system.

I believe it's thr RA drive,

I'd suggest taking the mount apart (at your friend's own risk!) and seeing if anything is even slightly mis-seated, warped, bent etc. A good clean if it needs it might further identify the problem.

Yep, I said that to him too

Perhaps the worm and gear are slighly out of kilter with each other?

If, God forbid, something large, solid and metallic has been bent it might need a trip back to a dealer or manufacturer.

Yeah, this might be the only way....
Thanks Dave,
Keith..

Keith - if this turns out to be a problem with the motor, then I'd say a motor replacement would be worth looking at. It mightn't be that costly...

But sheck out the other stuff first - particularly the way the motor is meshing with the gears in the mount.

Its hard to think how the gears in the mount could be dodgy - unless they were always like that or its a mount that's taken a severe pounding or has always carried something way too heavy. I guess motors are less robust than simple mechanics and that seems to be the more probable cause.

Keep us posted and hope your mate gets it fixed. Must be really bugging him.

Cheers

Dave

Thanks Dave, It's a bummer alright :roll:

Keith..

Hi all, I'm posting this question on behalf of a friend of mine, He bought a second hand EQ5 motorised mount some months ago, and has a problem with the mount shaking each time the motor drive is turned on.

Keith,

I think this problem has affected a number of EQ5 and even some EQ6 mounts, believed to be caused by poor engineering tolerances in Synta's manufacturing of its stepper motors. I recall hearing that changing the frequency of the motors to reduce or eliminate the problem helped some owners but the best solution is to replace the motors with a new dual axis drive system.