DIY GoTo EQ 3-2 Mount Project

[Dave1]

So guys the only remaining telescope I have is my Skylight 60mm F16.7. I haven't had a mount for this telescope for about a year. So recently I decided something has to be done about this. So I went back through my photo's and decided the EQ3-2 was a very good match for the Skywatcher 60mm. So I found one complete with matching tripod and accessories secondhand for a fair price. The mount and tripod turned up today.

So I want a GoTo mount, I realised that I have most of the components to make a GoTo mount here. I have two EQ GoTo mount control boxes. With that said I only really need motors to drive the mount, mounts to mount the motors, and an battery pack, to power it all.

The motors that are mostly used with EQ 3-2 class mount is typically NEMA 14 or NEMA 17. Most people will use belts to drive the mount from the motors. There is another option though, planetary gearbox directly coupled to the EQ 3-2 worm drive. So I research all the options. I selected the option which provided the best tracking resolution. The tracking resolution with the set-up intend to implement is estimated to be right ascension 0.17 and declination 0.34.

The motors I'm going to use are NEMA 14 with 19:1 planetary gearbox. The mounts for the motors will hopefully be 3D printed. I can get the correct couplers 5mm->6mm.

 

 

[lenscap]

You've got off to a great start by finding an EQ3-2 on a tubular steel tripod. That is  much more stable than the stock extruded ally one. (smaller vibration amplitude and quicker to settle)

I haven't used planetary-geared steppers myself but I've read that they can have a lot of backlash.

Out of interest what type of controllers do you have?

Good luck with the build.

[Dave1]

I have used a Helios EQ 3-2 before but on a Berlebach Uni 28 tripod, so it will be interesting to see how it compares to this 1.75" steel tripod. Well these planetary geared motors apparently have only a small amount backlash in them. And somebody has already done this exact set up before that I am replicating. So I know it can work.

I have a George Cushing Onstep MiniPCBv2 with TMC 5160 and Teensy 4.0. I also have a Astro Gadget EQPower. 

[monkeypig]

I modified a very similar mount, a bresser model that I retrofitted with Onstep. I did use NEMA 17 400 step motors and belts. I really liked the Onstep system, and used this mount till I got my EQ6r-pro. I may retrofit the system on a CG5 I have, so I have a second larger mount. I have already printed the mounts and have the pulleys, it's just a case of getting round to it. I hope your conversion goes well! The Onstep goggle group is quite active

[Dave1]

So today I continued with this project. My Nema 14 motors turned up last week, which was surprisingly quick considering they came all the way from China.

About a week ago, I had a quick observing session, to test the mount as well as observe what I could, seeing was bad. The EQ3-2 did have a bit of backlash, which is normal for EQ3-2 built by Synta ( Skywatcher ), I've owned three EQ 3-2 mounts, one Skywatcher branded the other two Skyscan 2001. The Skywatcher mount I bought new. The Two Skyscan I bought secondhand. 

So today I stripped, cleaned, and regreased the mount. I also adjusted the worm drives for backlash adjustment. On both axis I now have zero backlash. So in all its all going very well. Next to do in the project is sort the motor mounts out. 

[wookie1965]

14 hours ago, Dave1 said:

So today I continued with this project. My Nema 14 motors turned up last week, which was surprisingly quick considering they came all the way from China.

About a week ago, I had a quick observing session, to test the mount as well as observe what I could, seeing was bad. The EQ3-2 did have a bit of backlash, which is normal for EQ3-2 built by Synta ( Skywatcher ), I've owned three EQ 3-2 mounts, one Skywatcher branded the other two Skyscan 2001. The Skywatcher mount I bought new. The Two Skyscan I bought secondhand. 

So today I stripped, cleaned, and regreased the mount. I also adjusted the worm drives for backlash adjustment. On both axis I now have zero backlash. So in all its all going very well. Next to do in the project is sort the motor mounts out. 

Can I send you my EQ5 to get the backlash out of it been trying for weeks but I am not mechanically minded 😃 

[Dave1]

Hi Wookie,

Haha, could you me close up photo's of the worm drives on both axis? @wookie1965

Dave

Edited January 4, 2022 by Dave1

[wookie1965]

7 hours ago, Dave1 said:

Hi Wookie,

Haha, could you me close up photo's of the worm drives on both axis? @wookie1965

Dave

I would have strip it down again I'm waiting for a clear night to try it again. 

If I centre a object and press the right button then let up it keeps going for far too long. 

When I am viewing I can centre a object say Vega go to Capella come back to Vega and its not even in FOV. I have checked my polar scope that's Bob on and when I polar align its damn near close if not spot on as I am visual only I have a little leeway. 

Very frustrating I paid £85 to a well known telescope company to strip regrease and set up and it was great for 6 months but now seems to be getting worse every time I have taken it out. 

My son and I have just adjusted the worm gear so it's not tight but not loose it does feel better just need get it under the stars to try it. 

I appreciate you taking the time to help though. 

[Dave1]

@wookie1965 I see, I only asked to see photo's so that I could see if the worm drive is a similar design as the EQ 3-2. Both the worm drives on the EQ 3-2 are external and can be adjusted without stripping the mount down at all. On the EQ 3-2 worm drives there is a little grub screw which is for fine adjusting backlash in combination with the 4 worm drive mounting screws. Only tighten the worm drives up as tight as necessary to get a smooth operation in combination with the little grub screw. There is a tendency for people to over tighten the worm drive mounting screws, again do these only as tight as needed for the worm drive to operate with the least amount of pressure and no backlash. The 4 Allen head worm drive mounting screws on my EQ 3-2 are only just tight, and I use the term tight loosely. Before I take my mount outside I will probably be getting Locktite 222 thread lock, to thread lock those 4 screws. One thing to also bear in mind, is that nearly every internal nut was over tightened from the factory, even the nuts that hold the DEC and RA axis together. I literally only did them just tight enough so there was no lateral up and down movement along there respective axis, this made a huge difference to the performance of the mount. The lube Skywatcher uses, its the stickiest lube I've ever across, its utter crap. I hope Skywatcher has updated the lube it uses in its mount from the Skyscan era. 

Have you told the company that did the work for you?   

I see you have motors. Would going from target 1 to target 2 then back to target 1 be a tracking error on part of the software rather than hardware issue? Have you checked all you settings in the software?

Edited January 4, 2022 by Dave1

[wookie1965]

Yes checked the handset firmware is up to date and the gears sound exactly the same we have adjusted those Allen screws and the grub screw and you are correct the nuts inside where very tight had to adjust them too so that they were not tight but with no play. 

[astrosathya]

Hey, you can use the WemosD1 CNCV3 OnStep Controller easily. Here is a link of someone's build. I built the CNCv3 version too. works well.