Jump to content


Let's get rid of the BL on the HEQ5 mount! A very simple way to do it.

Recommended Posts

  • Replies 32
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Hi to all. The most popular mounts - even those that are included in  the small-medium range group, do drive the axes rotation  via worm wheel coupling .  This one are plagued by the drawback t

Just three preliminary notices:  - I take no responsibility in case of damage to your mount. I recommend these procedures to those who have a minimum of familiarity with the manipulation of mecha

Hi Kathleen. In reality the backlash due to the small gears  before the worm gear coupling is not so significant. On the other hand, the complicated combination of eccentricity and irregular

Posted Images

6 minutes ago, cuivenion said:

Hi, yes I meant the main gear that meshes with the worm. vlaiv gave a good explanation in an earlier post.

Thought so, then this is the error the modification should address, all being well.


Link to post
Share on other sites
Posted (edited)
2 hours ago, SpookyKatt said:

Many thanks for this thread, its interesting and the video is useful in explaining the final proposed operation.
I'd have thought the first step in removing the backlash would still have been to do a belt mod, are you going
to do one as well to the mount as there is still a source for backlash between the gears between the motor
and worm ?


Hi Kathleen.

In reality the backlash due to the small gears  before the worm gear coupling is not so significant.

On the other hand, the complicated combination of eccentricity and irregularity of those gears tends to produce  a PE that is not easily correctable as it is almost unpredictable, so we cannot  counterbalance it by an easy PEC algorithm.

The most important backlash is that produced by the worm gear. My modification is effective in eliminating it, no matter if the large worm gear has eccentricity.

This mod - as Vlaiv correctly wrote - is based on a worm gear floating contact produced by the spring. 

Spring pressure force does not change at all, because  the eccentricity-related gear deviations remain within very small phisical limits (a tenth of a millimetre range). 

It is  absolutely irrelevant  in the sense of a pressure change  between the W/G  coupling.   This problem unfortunately occurs with tuning screws.


Edited by benzomobile
  • Like 2
Link to post
Share on other sites

Hi Benzomobile,

Ah ok, thanks for that, I get the benefit of the floating worm and how that resolves eccentricity, but had just wondered
about the effect of the rest of the gearing.  A nice solution though I have to say.


Link to post
Share on other sites
22 minutes ago, SpookyKatt said:

Hi Benzomobile,

Ah ok, thanks for that, I get the benefit of the floating worm and how that resolves eccentricity, but had just wondered
about the effect of the rest of the gearing.  A nice solution though I have to say.


For both BL and PE,  belts & gears transmission  is  a pretty good  solution, but  'no gear/no belt'  one, i.e. the direct friction, or harmonic design (this one is very expensive!) are absolutely the best ones 🙂


  • Like 1
Link to post
Share on other sites
Posted (edited)

Hello to all, girls and boys  🙂

Now it's time to deal with:

Tuning  and everything else ...

You need:
- some wooden toothpicks (yes, you read that right!)                                                                                                                                                                                                                                                                                               

- always the same Uhu Plus resin (heaven bless it)                                                                                                                                                                                                                                                                                                           

- 6 hex M5 x 30mm stainless bolts shorter than the current ones
- 6 M5 x 5mm stainless grubs  (see pics below - note that I have removed the worm assy so that everything is clearer) 

IMG_20201216_142338.thumb.jpg.b8c84ea7b83f7cc9ffe6e531640148cf.jpg                               IMG_20201216_142212.thumb.jpg.94c1c506768e43072cec7d81fdc67f7a.jpg


As I said before, the worm holder bolts should not be tightened. Why?  The worm assy does not need to be tightened on its bearing surface, BUT it does need to be able to slide smoothly on it, permitting only a little gap beetwin each other.
As you will see, the places where the bolts are inserted are wider than the bolts themselves. This is why the bolts - when not tightened,  allow the worm assy to move (it traslate) about one millimetre in each direction.           

It is of interest to us that this translation  occurs in one direction only, and this direction is exactly perpendicular to the worm mechanical axis. 
Now let's see how to force the worm to move in that direction ONLY  to mesh gear  in FLOATING mode and  in the best possible way.
We need to adjust the bolts in a stable manner, build the pivots and adjust these as well.


1) adjusting the bolts

You need to insert the three short  M5 grub in the bolt screws. 

After epoxy resin  melting,   place a small amount of it  on the tip of a toothpick, taking care not to touch the walls of the three threads on the base of the RA axis block.                                                                                        

You must deposit the resin on the deepest part of the threads (5-6 mm from the bottom). It is necessary to repeat this operation several times so that the resin is evenly spread where I have told you. 
Having done this, first screw the grubs into their seats until they get smeared with resin too, then unscrew them by 4-5mm.                                                                                                                                                               

Don't worry about the grubs sticking straight away as it takes at least three hours for the resin to cure a little. The grubs serve as a stop for the bolts so that they can be fully screwed in, while still allowing the worm assy to slide over the underlying bearing surface without excessive gap (half a mm is ok).  When you screw the bolts over the grubs and all is ok, please, do not tight these, for now. 

After epoxy get cured, only then you can do tight the bolts to complete the final assembly. 

I understand well this operation is the most tedious, but it is also the most delicate to reach a  successful mod.

You will have to do a few attempts to get each grub placed at the correct depth.                                                                                                                                                                                                                                     

If the  worm assy gets stuck or slides unevenly, you will have to pull up the grubs (always one at a time). Otherwise you will need to push them deeper. This is fine tuning, so try screwing (or unscrewing) in the grubs just half a turn at a time.

Have fun ... like I did 🙂

The story will continue soon.


Edited by benzomobile
Link to post
Share on other sites
Posted (edited)

The hole on the holder is of necessity larger as the rod, why?   

That's because the rod must be inclined in the best direction before it can be fixed in place.  This 'trick' is essential so that the worm holder's play can be minimised. 

Let's see how to proceed  (pics below refer to Dec axis)



Degrease (alcohol or acetone are ok) both the stainless steel bushing and the bare metal area around the hole.

Apply a thin layer of mixed epoxy resin  all around the hole up to about one millimetre from its edges (no resin should get inside).  
Apply a very thin film of lubricant along the rod. Insert the rod into the bushing to make the pin and leave the grub loose.
Once this is done, insert the pin into the hole as far as it will go and then retract it about one millimetre. Now tighten the bushing grub.
Place the second bushing on top of the rod anf tighten its grub.
Levering your thumb over  the outer bushing, while keeping your index and middle finger on the worm holder (do not apply any force on another part of the mount body!), try to tilt the pin sideways in every direction while simultaneously rotating the worm  between the thumb and index of your other hand. 
You will find that in a particular position, the worm will spin smoothly and without backlash.

Well, now you're where you need to be! Use a rubber band to hold the plug in that position until the resin get hard enough (see pics above middle and right).
When the time comes, remove the rubber band and add every two to three hours just a little bit of resin (if it's too much, it drips!) all around the inner bushing base and border (but stay away from the grub!),  until it forms a small block like in the photo below left.  When epoxy cured, you can remove the grub.  The pin can then be pulled out to check that it is not stuck and then repositioned (see pics below, middle and right)


                        IMG_20210408_170332.thumb.jpg.d86064d2c5ba94f9337f540567e95492.jpg                      IMG_20210408_170404.thumb.jpg.5efb9e40f1ad93c68ee01675523723fe.jpg


After you've correctly insert RA axle bar/gear smooth part inside the RA block (please do lubricate well these parts and don't forget the washer), 
do set the lower conical bearing and screw the large lock nut, the RA graticule ring and the polar scope carrier ring. Mod on RA axle is done. Don't forget to tight all grubs.

Do the all above operations on both axes.

When eventually Dec axis adjusting task is completed too, you can slip its bar/gear smooth parts (do lubricate!) inside their seat (don't forget the washer). 
Do set conical bearing and screw the counterweight collar. Do insert the counterweight shaft before the dovetail carrier.  Do tight all grubs.

Finally, I must tell you about the modification of the socket panel.
See you soon







Edited by benzomobile
  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Astrofriend
      Last night I could do my first test with a Raspberry controlled HEQ5 mount. Worked much better now compare with all problem I had one year ago. I succeeded to: Plate solve, auto focus, take images. What's left to fix, auto guiding, GPS module to communicate.

      Tonight it looks to be a clear night too. I will do a new test run, concentrate me on the auto guider, now in the beginning I use the internal guider, later maybe I change over to PHD2. Very exiting.

      My setup of HEQ5 and a 300 mm Pentax 645 lens:

    • By JenP04
      Please forgive me in advance for my newbie and potentially frustrating question here! 
      I have got an HEQ5 mount for my skymax 180 that I was given for Christmas. We have tried following many YouTube videos and reading what we can to get this set up and polar aligned and feel like we are missing something fundamental as when we go to then star align with the GOTO remote, it points at the floor instead of the moon or the star we are trying to align to. So far we have used 5 freezing nights of trying to do these things to no avail and it is rather frustrating and extremely disappointing!
      So I am wondering please, what is the best way for me to actually set this thing up so we can finally enjoy using the scope? Do I need to have Home position sorted before I've aligned so once we have (hopefully) done that then we can navigate everything easier? Is that potentially what we are missing? 
      With lockdown i dont have a handy shop to visit or anyone else that knows how to do this and while I am sure patience is a virtue, I feel so overwhelmed by it all! Any advice or recommendations on what to watch or do to help us are gratefully received!
      Again, I am sorry for being such a newb, I am hopeful once we crack this it will become second nature over time! Thank you!
    • By SStanford
      Hi All,
      With ongoing issues related to slewing in the EQ3 pro it's quite clear that there is some significant backlash.
      I understand there is a way to repair this myself; does anyone have details of guide for the EQ3 pro to reduce the backlash?
      I also understand that the lubricant is important to reduce backlash. Can anyone make any recommendations here too?
      Thanks again!
    • By Astropedro
      Looking to buy either an NEQ6 or a HEQ5 mount.  Im in Cheshire but dont mind paying for delivery/postage.  Would consider a good imaging scope or setup too.
    • By AstroRuz
      For sale is my beloved but now superfluous to requirements HEQ5 Pro for £650
      It's in a used condition as you would imagine. I've had it for about 4 years and found great success with this mount. Ideal for those beginning astrophotography and also good for visual users.
      I'm calling it "deluxe" due to the upgrades I've had done.
      - It's belt modified
      - It's had brand new bearings and grease
      - The backlash has been expertly setup 
      - It has the latest polar scope
      - The power port has been replaced with an aviation style port which is a lot more secure
      It'll come with the hand controller and at least 1 counterweight (if I can find the second it'll come with both). The polar scope cover has been lost. The counterweight is rusty as always. There is some marring on the counterweight bar housing as shown in the photos.
      It also will come with the modified power cable required also.
      Note: the power LED sometimes doesn't illuminate but the mount is still powered (please see the photo with the hand controller).
      Collection or local delivery within Northampton

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.