HEQ5 RA "Wobble"

[samtheeagle]

I'm starting to worry about my mount  I've got a quite significant wiggle in the RA axis when the mount is powered off in it's parked position (clutches locked of course). Before I embark on a full strip down following Atrobaby's guide I thought it would be worth asking if anyone had suggestions for a less drastic investigation / fix?

I'm not sure how recently this issue has come up, I've only just become aware of it after an equipment upgrade. I've just replaced my guiding setup of a 50mm finder coupled with an SPC900 webcam, to a Celestron 70mm TravelScope with a Touptek Mono guider. When I made this change my guiding went to hell, with a crazy amount of oscillation on the RA axis, which is what led to to start looking for flexure etc. and thus I found the RA axis slop...

Now I understand that my new guiding setup has a much tighter FOV, and therefore will make the guiding errors look more pronounced than I am used to with the finder guider setup, but still I'm getting graphs with massive errors and corrections, sometime 2-3 pixels worth of motion. The DEC axis looks ok, but RA is all over the place, and I wonder if it's down to this wiggle? I've tried adjusting the balance so that the mount is at least always working on one direction, but that didn't appear to help much last night.

So can anyone offer me some advice?

Thanks in advance

[Starlight 1]

The HEQ5 mounts do have about 1 or 2mm on head .

39 minutes ago, samtheeagle said:

Celestron 70mm TravelScope

How well is this scope lock down, is it pigy back or side by side.

39 minutes ago, samtheeagle said:

adjusting the balance

Keep this spot on in RA/DEC. and in PHD put the trendines on  so you can see how the red and blue is moving up or down.

 

PS have you put the right setting in PHD for the new scope and camera,

Edited April 30, 2016 by Starlight 1
add more to post

[Owmuchonomy]

This is not unusual.  Before you strip it down, do the RA worm play adjustment process, also described on Astrobaby's site.  Also, check the worm bearing locking rings are reasonably tight (under the plastic circular removable covers).  It may be just that, that needs some fettling.  http://www.astro-baby.com/heq5-rebuild/heq5-we1.htm

[PhotoGav]

I have just had the same problem with my HEQ5 mount. I have made quite a few changes so don't know exactly which change has had most curative effect, but my mount is now performing pretty well. I did the worm adjustment process as described on astrobaby's website yesterday, not the full strip down and rebuild, just the worm tightening and it has definitely helped to improve things. I was worried about tinkering with the mount, but it really wasn't too frightening in the end and the mount still works! The only word of advice I would offer is that when you remove the power panel, if the leads are very short and you can't move it away enough to easily get at the worm screw, take the lid off the mount and release the cables so that the power panel can move further away. Also, don't overtighten the worm adjustment screws, make sure you move the mount in all directions to check for binding (it's a very obvious squealing noise when you hit a binding point!). I found that my DEC worm was a bit too tight last night, so had to ease it off a fraction at about 1:15am! It did make a difference to the Dec guiding.

Good luck.

[samtheeagle]

Thanks all for the advice! 

@Starlight 1 - The new guide scope of mounted in a piggy back fashion, all firmly bolted down. Not even guide scope rings... And yes, I reset PHD2 to default settings and then set it up for the new scope & camera combo, so that all looks good.

@Owmuchonomy - Good to know that it's fairly common and nothing too untoward, hopefully.

@PhotoGav - Thanks for the binding tip, I had always wondered and worried if I'd over tightened things, but I've never heard any squealing, so if anything things may be too loose.

Good to know that I can try the RA worm gear adjustment without too much stripping down... I did follow the whole strip down process when I got this mount secondhand, just to check it out and clean out the default nasty glue pretending to be grease. But it's been a long time since I have looked at the guide. I shall attempt to give the mount some TLC over the long weekend, and test it out when we're next graced with some clear skies.

One thing that I did find when checking out the balance of things is that my DEC axis is very heavily out of whack... And I have no possibility to resolve it atm, I need to get an extra long dovetail so that I can shift the whole setup forward a bit. Right now the securing bolts are up against the saddle, and the scope is as far forwards in the rings as it can go... So a quick order to FLO incoming

Thanks again all, will update as and when I have any further news.

[Starlight 1]

42 minutes ago, samtheeagle said:

One thing that I did find when checking out the balance of things is that my DEC axis is very heavily out of whack... And I have no possibility to resolve it atm, I need to get an extra long dovetail so that I can shift the whole setup forward a bit.

This is why I allways have Trendines on so you see when balance is not right + your guiding will never work for more then 2 or 3 mins. just put this right and you all done.

[TerryMcK]

I too got the dreaded RA wobble on my HEQ5 Pro (Rowan belt mod) and thanks to AstroBaby's website was able to fix it.

A slight adjustment of the two grub screws she mentions (after loosening the bigger cap head screws) made everything good again.

 

[newbie alert]

23 hours ago, TerryMcK said:

I too got the dreaded RA wobble on my HEQ5 Pro (Rowan belt mod) and thanks to AstroBaby's website was able to fix it.

A slight adjustment of the two grub screws she mentions (after loosening the bigger cap head screws) made everything good again.

 

Yes adjusting the worm would be my first port of call

[Dan13]

On 22/11/2019 at 14:50, TerryMcK said:

I too got the dreaded RA wobble on my HEQ5 Pro (Rowan belt mod) and thanks to AstroBaby's website was able to fix it.

A slight adjustment of the two grub screws she mentions (after loosening the bigger cap head screws) made everything good again.

 

I'm struggling so hard with this and it's driving me nuts!! I get it so the head has no wobble. I can also turn the belt cog and the dec will move nicely but when I try to kove the dec head by hand its stiff and binding! I've tried every thing please help! 😒

[Kev M]

Definitely needs the grub screws adjusting, its probably stiff when you move the belt cog but the gear ratio is so much in your favour its not noticeable.

Adjust them again to get it rotating freely but not wobbling, probably need to restart entirely with it completely loose and them work into it ,one side at a time so its central.

[Martin AB Cohen]

I have just created this video on my YouTube channel about identifying and fixing Backlash on your mount.  You may find it helpful.

https://youtu.be/x79akiJO3pU