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Possible motor drive problem


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Just realised i posted this in the discussion section by mistake so am posting it here now :evil6:

Folks,

I have an Skywatcher Explorer 150 on an EQ3-2 mount to which I have added the standard dual axis motor drives (the best thing I ever did!). I made the most of the clear weekend and spent several hours on Saturday evening and then Sunday afternoon observing and everything was normal, I took some long exposures of orion, pleiades, jupiter and the moon as well as some general observing.

However on Sunday evening I started with Jupiter and when I tried to observe using a 6mm eyepiece I noticed jupter was a bit blurred but most noticeable the moons all appeared as mini star trails! There was some vibration somewhere and it didn't damp down. The first thing I did was switch of the drives and hey presto the moons become pin-points of light. HAs anyone else come across a problem with the RA motor vibrating instead of moving smoothly? STrangely when I put the motor into x2, x4 or x8 speed there didn't apear to be any vibration.

I spent some time last night making sure everything was still securely connected, screwed or fastened, chose a different power source and pretty much exhausted anything I could think of.

Any ideas? :)

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I've had exactly that same problem with an EQ3-2 and dual axis drives. I blamed it in part on the large (but light) OTA I was using, an f6 8" newtonian, which I assumed was resonating with the stepper motors. I'm afraid my solution was a bit radical -sold the EQ3-2 and bought a second hand Vixen GP and some MT1 motors. Sorry not to be of more help...

Edited by Ludd
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Hi Chris - yes it's quite a light tripod. You should make sure all the tightening bolts on the legs are firmly done up and the mount attached firmly and locked onto polar alignment. Maybe your clutches were loose? They should be locked firm when using the motors.

You could also try hanging a heavy weight off the tray under the scope (couple of bricks in a string bag eg) which should help a bit. Also ensure the dovetail is firmly attached to the scope and the tube rings firm enough without crushing the tube.

Just some ideas :)

Edited by brantuk
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Thanks for the advice guys. I didn't focus on the multitude of fixings on the tripod so have been round everything and some were giving enough play to be the possible cause. And I have made sure it's balanced well too, although I did this a couple of days earlier. Just need to wait for a chance to try it out again and double check the clutch locks.

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  • 3 months later...

Having received a PM about this I thought I ought to post a message about the outcome.

Brantuk's advice was spot on I think. There had been quite a bit of slack in some of the bolts holding the tripod to the base of the mount and in the screws fixing the top of the tripod legs. Next chance I had to look at Jupiter and many recent nights looking at Saturn everything has been just fine. :)

A valuable lesson I think.

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