Some backlash questions

[swag72]

Backlash ............. A word I keep reading and something that has caused me some worry over time. I am trying to understand it, as well as potentially eliminate it and find out what other issues, apart from backlash can cause mount movement or instability.

Let me explain. I have an HEQ5 and when the DEC clutch is tightened, I can hold the scope and I Have about 1/8th of an inch of movement or 'wiggle'. Reading on the net, fatal I know, this article ( http://www.harrisont...ed_Focuser.html) suggests that I have backlash and it can 'easily' be cured by adjusting the worm gearing and gear wheel. When we did that, the whole thing jammed up upon using, so it was too tight. But, even when it was too tight I still had my movement on the DEC axis. I can not seem to eliminate this movement.

I can't help thinking that this is something other than backlash, and so we stripped the DEC axis down in a hope to tighten up something that was perhaps loose, but nothing tightened up.

So what else could it be other than backlash? What else would cause the classic symptom of DEC clutch tight, but still getting movement in the scope?

I am a fiddler and if something isn't causing me issues, I should leave it alone, but it's niggling me and I want to try to understand what it could be.

Interested to hear your thought on this - What could it be?

[olander08]

I just noticed this on my HEQ5 last observing session, but I haven't stripped anything down yet.

Definitely following this thread!

[RogerTheDodger]

I know you drift align, get that right and you shouldn't be guiding in DEC at all...

[Steve Ward]

I had some play in both RA + DEC on mine ,

Everyone kept saying it makes no odds but on a windy night it was a nightmare.

Sorted it out in 5 minutes by very , very small tweak to tighten up the worm meshing , less than an 1/8 turn on the grub screws.

Now get no 'flapping' about in the breeze so's to speak even with the 200PDS and 80ED Pro dualled up , wish i'd bitten the bullet and done it a year and a half ago.

Thanks to Ralph at Astronomy and Nature centre for the advice and directions........

[swag72]

When I tightened the worm mesh (so that it was over tight I later found out) I still had the movement on the DEC axis when the clutch was tight. That's what makes me think that perhaps it's not backlash. Surely if the worm mesh was too tight, I'd have eliminated the play in the DEC?

Adjusting the worm gear has no effect whatsoever on my DEC wobble.

[swag72]

Out tonight just messing about and here's what I notice - When I move the RA axis (E or W) the movement on the star on the screen is instant and smooth and the mount sounds nice and quiet. When I use the N and S (DEC axis) the movement isn't instant, sometimes the star is staionary for 5 seconds despite moving the mount, and I can hear the mount movinf. Then when the star does get going, it can be erratic movement. It happens the same in N and S.

Does this sound like backlash?

[Rustysplit]

Sara,

I had similar issues with my Neq6. If you have tightened the mesh and it still moves, it could be the worm gear end float needs tightening. I found it was best to adjust this first, then tweek the actual mesh.

On the eq6 the adjuster is under one of the black caps on the side, Not sure on heq5, but I am pretty sure that a quick look on Astrobaby's site at the heq5 tuning tips should help.

If the end float is too great, the scope will move side to side as the actual worm gear gets pushed to each end of it's free travel.

Good luck!

[Peter Drew]

I'm sure that what has already been mentioned i.e. the wormshaft end float is the answer but it might also be worth checking that the dovetail puck is tight as the grub screws holding this can become loose after a while.