HEQ5 rebuild woes

[Padraic M]

Hi all, creating a new topic for this so I don't hijack either the Anyone Imaging Tonight thread or GazAstro's other HEQ5 topic.

 

Background: HEQ5 Pro, astrobaby tuned and Rowan belt-modded, was giving me guiding of around 1.5". For reasons I now regret (!) I decided to go ahead and to replace the stock bearings on the RA axis with top-quality SKG bearings. The process was fairly straightforward, using Astrobaby's instructions again, and better quality SuperLube grease.

The first results were disastrous - on the first night out I was plagued with equipment disconnections and general belligerence, including camera fails, mount refusals, but mostly telescope disconnections in NINA - lucky to get a connection to last for 30 seconds. Also, NINA doesn't like when things go wrong, so it hung, crashed, locked profiles, reset to factory settings, and eventually I reinstalled it from the last stable version. So, completely unusable, and very hard to make any modifications in the cold and dark.

I re-stripped the following day, checked everything, applied more grease, and re-tuned the worm backlash to be slightly looser. There's a noticeable amount of movement in the axis now, but definitely no binding. I also loosened the RA worm end float slightly.

 

Because so many different things went wrong, with no logical connection between them, I worked on the theory that tight bearings were causing the mount to draw too much current, and supply voltage was being pulled down below 12V. That would definitely cause random failures and drop-outs, especially with the mount. I'm not convinced now that that is the case; the power supply is the Nevada Radio 30A. I'm using the front 10A cigarette socket, and am drawing less than 4A at peak (both axes slewing; camera cooler and two dew heaters on). With the hand controller connected to the mount, supply voltage varies from 12.8V at no load, to 12.5V at full load. 

 

Needless to say, everything works absolutely perfectly under test inside in the warmth!

 

Second night out was better, but still not usable for imaging. I connected everything gradually and monitored power usage at each stage. Using the hand controller at first, the mount slews happily in all four directions, with no stalling and no unusual noises. Powered down, switched out the HC for EQMOD PC connection and rebooted. All equipment behaving better, and NINA connection holding stronger, but still had a disconnect. I held off on connecting PHD2 as I had a feeling that the problems were worse when guiding. I remembered that while all of the other problems were happening, the PC would freeze up from time to time for about 6 seconds, then continue. 

 

Un-guided 60s subs were star-trailed. As soon as I connected PHD2 and started guiding, the NINA "telescope connection lost" error started again. Not as regularly, but regularly enough that I couldn't leave the PC unattended. Interestingly, neither ASCOM nor PHD2 lost their connections, just NINA.

 

I focused in on PHD2. Cleared calibration data and recalibrated. Tried a test sequence on Bode's which is nice and high, and free from the worst of the light pollution in my garden. Scope W facing E was ok - generally got ~2.4" guiding, with two disconnects over a 10x60s sequence. Better than nothing, but worse than it was. Restarted the sequence and obviously Bode's had crossed the meridian so slewed to Scope E facing W. Now it failed entirely to track. Regular 'telescope connection lost' errors in NINA, and PHD2 'unable to make sufficient corrections in RA'. Screenshot below - notice the funky guide graph.

 

Now I think the key phrase is 'check for problems with the mount mechanics'. 

 

Current theory is that the mount RA is either binding in the cold temperatures, or has too much RA backlash to make the necessary adjustments. PHD2 is trying to compensate, and is sending multi-second pulses to the mount. Can the PC freeze while waiting for the mount to respond? I suspect the telescope connection to NINA is timing out because the PC has frozen.

 

So, how can I tell if the worm is too tight or too loose? What's the interaction between worm tightness and worm end-float? My best guess at the moment is to loosen both the worm and the end-float on the basis that binding is more likely to cause these problems than backlash is. If I can get PHD2 to behave a little better, then I can measure backlash and attempt to adjust for it.

 

Finally, has anyone had the same issue with the PC freezing for a few seconds at a time? It's a new laptop, i7 core, lots of RAM and SSD drive. New USB 3.0 StarTech hub.

 

 

 

[Padraic M]

I should also add that the SKG bearings are noticeably stiffer than the stock bearings, both straight out of the bag and when greased up and installed. They're also not quite as snug on the RA shaft. But the mount head is rotating smoothly now that I've added more grease.

[AstronomyUkraine]

2 hours ago, Padraic M said:

So, how can I tell if the worm is too tight or too loose? What's the interaction between worm tightness and worm end-float? My best guess at the moment is to loosen both the worm and the end-float on the basis that binding is more likely to cause these problems than backlash is. If I can get PHD2 to behave a little better, then I can measure backlash and attempt to adjust for it.

I did a belt mod on my EQ6. When checking for backlash and binding, I tightened the end float until it started binding, then loosened it off slightly, until the mount rotated freely. Then I did the same with the worm adjustments, just easing off very slightly, until I had no binding. Another problem you might have in this cold weather, is metal contracting, causing slight movement in backlash. If your scope is stored in a warm house, maybe you need to slightly adjust the worm on cold nights. Aluminium contracts quicker than steel, so the aluminium mount would shrink slightly, tightening on worm. That's my thoughts anyway.

 

Have you tried your setup on another capture software, just in case it is NINA causing the problems?

Edited March 1, 2021 by AstronomyUkraine

[Padraic M]

Thanks Brian, that sounds like a good plan of attack. 

1 hour ago, AstronomyUkraine said:

Have you tried your setup on another capture software, just in case it is NINA causing the problems?

I've used APT for quite some time, before the rebuild, without any issues. However, I've also had some full nights with perfect operation with NINA, so I don't think it's causing the problem - although it is reacting badly to it! Worth sticking with NINA just for the autofocus routine.

 

I do have a vague memory of the 'PC freeze' happening even under APT, but never paid too much attention to it before

[GazAstro]

As I got sick of spending so many nights piddling around with mine I sent it to Dave at Darkframe ... If it helps, I would say that he has my worm adjustment probably tighter rather than looser than I had it with my attempts.

This is just gut feel obviously and he has certainly improved mine to the extent that its way more stable in PHD and feels better.

Cant remember the figures but when I was adjusting worm mesh before I sent it to him I experimented with using an ammeter to measure the load increase as I tightened the mesh then backed off til it just dropped back down.

It's higher now than before I sent it indicating (in my mind) that it is indeed tighter.

 

Wish you all the best with yours ! seriously frustrating when everyone else has a good HEQ5 but yours isn't.

 

[Padraic M]

Thanks @GazAstro on the one hand I'm sorry I started as I'm spending so much time trying to resolve, but on the other hand I'm still optimistic that if I do crack it I learn more about the process and hopefully be able to maintain it correctly in future! At the moment, if I could get it back to reliable guiding at 1.4" I'd be very happy. 

 

I don't fancy sending the mount by international courier to Dave... !

[GazAstro]

36 minutes ago, Padraic M said:

Thanks @GazAstro on the one hand I'm sorry I started as I'm spending so much time trying to resolve, but on the other hand I'm still optimistic that if I do crack it I learn more about the process and hopefully be able to maintain it correctly in future! At the moment, if I could get it back to reliable guiding at 1.4" I'd be very happy. 

 

I don't fancy sending the mount by international courier to Dave... !

No ! I wasn't suggesting you send it 😲 just comparing his ( vast knowledge ) results on my mount to my own.

[Padraic M]

Spent a few dark cold hours tinkering with the setup over the last few nights, and a pattern is emerging in relation to USB loading. I simplified the USB connections with more direct-connect to the PC (unfortunately only have 2 USB ports on the laptop); left the focuser unconnected and plugged the 1600mm directly into the PC. The EFW is plugged through the 1600mm. That leaves the mount EQMOD cable and the asi290mm mini guidecam through the Startech USB3.0 hub.

 

The disconnects almost went away, but unfortunately still happen regularly enough that I can't leave the mount unattended. Of 10x 150s lights last night, only 2 of them were usable, all others were star-trailed.

The pattern now is that every minute or so, I see one or more of:

- PHD2 'Pulseguide command to mount failed'

- PC 'freezes' for ~6 seconds and PHD has to issue lengthy pulses to mount to get it back on track.

- NINA 'telescope connection lost'

Posted on the NINA forum and the guys responded immediately and emphatically with 'Cables'. 

So, a bunch of new Startech USB cables are on the way from Radionics. 

 

I think this will sort out the disconnects, but may still leave me with poor guiding. The mount is handling perfectly well with the hand controller, so I think the backlash and binding are reasonable, but when the guiding was behaving itself last night, it was achieving ~1.8" which is a little worse than it was before I swapped in the SKG bearings. I believe that if the new cables sort out the mount disconnects, I'll be able to see more clearly that the mount tuning isn't perfect. The question will be whether I want to put the stock bearings back in or try to tune up the SKGs properly. But that's a question for another night!

[TerryMcK]

The PC freezes do sound as though something is amiss on the PC and is compounding your problems. This is one of the prime reasons I went away from using Microsoft operating systems as an acquisition platform. I use Linux now on an Astroberry loaded Raspberry PI. PHD2 is still available on the PI and the only time I see disconnects now is if it has clouded over and it has lost guide stars. Then it pops up with a message saying something like "disconnected from the camera but will reconnect automatically" which it does.

 

I know a lot of people dedicate a PC running Windows to just doing data acquisition, do not connect it to the internet, rarely upgrade anything on it, no anti virus etc and seem to run without problems. That is fine from my point of view but I still moved to an alternative.

 

One thing that has improved my rig no end is having a powered USB3 hub on the HEQ5 Pro mount itself rather than a distance away. Then I run an active USB3 cable from the mount to the computer which is in a lidded box, along with a ethernet switch and the power supply. I have a long EQDIR cable and run that to the computer too. Although that could have just been a short one running to the USB3 hub. This has minimized any issues due to USB connectivity issues.

 

Below you can see the hub next to the focuser box. They are both fixed to the head using ultra heavy duty velcro

 

 

On the other side of the head is a dew controller/power supply box and I have used that little box on the right hand side to step down 12 volts to 5 volts for the USB3 hub. I got that from Amazon for a few quid. Again the gear on this side of the head are also fixed using velcro. Needless to say there are a lot of cables on the head and I have shortened them to suit, or where I can't have carefully wrapped everything. 

 

Edited March 8, 2021 by TerryMcK

[Padraic M]

Thanks @TerryMcK it's always great to see close-ups of working setups. I've an order of good USB cables on the way, in short lengths, for connection to an on-mount powered USB hub, so that'll be step one. I'm hopeful that it will improve things. After that, if it's working in an acceptable way at all, I will probably leave it at that for now and try to actually get some images in!

Migrating to a Pi or a miniPC is on the long-list but I'm not keen to tackle it just yet. 

I hadn't considered sticking the dew controller to the mount but having seen yours I probably will do that too.

[jiberjaber]

A long time ago I used to have problems with a ground loop on my HEQ5Pro esp when there was a switchmode power supply involved.  Have you tried running with the laptop on battery power only to see if there is a difference?

 

At the moment I'm running a PI4 4GB with stellarmate and the devices all off that with no USB hub (ZWO EFW, EAF, ASI1600MM, QHY5M-II guider camera, Mount control USB to Serial).  I found making sure you've got enough cable cross sectional area to reduce voltage drop to the mount is quite important if you have a long run (mines about 10m of 2mm^2 cable)

I get the odd mount disconnect but I think that is related to a repair I had to make to the mount control board.

With the belt mod and re greased RA bearings  (I couldn't get the DEC open!) I get good guiding - but it can depend a lot on conditions...

 

[Padraic M]

@jiberjaber interesting idea. I need to confirm/refute the USB theory first but will consider this if I still have problems. Have a whole new set of USB cables ready to try out, if I ever get a clear night again. It's been so patchy since the New Year and I'm spending most of my imaging time testing.

[Padraic M]

Just to follow up on this thread, and for the benefit of others suffering in the same way in future, here's the latest happy update.

 

I received a full set of good quality replacement USB cables from Startech, in lengths of 0.5m and 1m selected to suit each device. These are now in place, with a Startech powered USB 3.0 hub velcroed to the mount head. I also ordered a new 5m Lynx Astro EQDIR cable (FTDI chip), which I connect directly to the PC rather than through the hub. Cables are secured reasonably well in velcro looms to avoid any hanging or snagging. I also switched the laptop into Airplane mode, in case there was any network-related timeout trying to connect to a distant wifi AP.

 

Happy to report that everything is behaving perfectly now! On the second night out, I didn't switch to Airplane mode, and it continued to work well, so I can eliminate that from my investigations.

 

My conclusion now is that EQDIR had issues communicating through the USB hub, presumably while the guidecam was also transmitting frames, and the regular '6-sec lock-up' was a USB timeout or collision of some sort. NINA possibly is less tolerant of the lock-up than APT and other software, so dropped the mount connection. I also suspect that PHD2 was issuing commands to the mount that were not being acted upon so it was confused if there was a lot of backlash, or if the mount was offline.

 

As an added benefit, I also upgraded PHD2 and am using multi-star guiding.

 

My guiding is now consistently around 0.7" and is rock-solid. RA and Dec RMS errors are very close, and I have nice round stars. I have had a number of good nights imaging where I can leave the rig running unattended while I get some sleep! I've even managed a number of successful meridian flips

 

Given the performance of the Dec axis (I can get long periods of guiding with no Dec movements) I'm reluctant to swap out the stock Dec bearings and install the SKG bearings. I'm afraid that this might impede Dec guiding, and even if it improved guiding, I would again have different RMS errors on RA and Dec and potentially bean-shaped stars. It's working now and I probably can't expect much better from a HEQ5 so I'll leave well enough alone.

[TerryMcK]

That is great news Padraic.

[Mike Diskett]

@Padraic M

Well here I am with exactly the same issue.

Pc pauses,  same pdh2 errors.

I have a direct connection from pc to mount via rj45 dongle thing (no hub).
All works inside in the warm, outside it all goes terribly wrong after about 30 mins.
(Its about 5C outside)


Have changed all my cables except the dongle. no Joy

Tried putting dew heater on the 12V power supply, just incase it was cold causing a voltage drop.

It seems to me from your description of the solution it was likely the new EQDir cable.

 

[Padraic M]

@Mike DiskettI think you're correct. I can reproduce the problems if I connect the EQDIR through the hub, so I'm left with two USB cables between the mount and the laptop. I've also acquired a Pocket Powerbox Advance recently, but can't get EQDIR to work through that either.

 

Edit: I just re-read your post; I can't swear that the new EQDIR cable made a difference other than allowing me to connect directly to the laptop, which I see you are already doing. I can't test between the two because the old cable is only 1m so won't reach. But it definitely doesn't work through the USB hub.

Edited June 13, 2021 by Padraic M

[Mike Diskett]

@Padraic M I decided maybe it was my power supply, perhaps outputing a flakey voltage that interferes with the USB comms electronics.

For good measure I got a 14V one as apparently the extra few volts can help with tracking.

Did not help.

So then I tried replacing my mains power 10 meter extension cable with a heavy duty 20 meter one. and plugging it into a different socket in the house (internal socket instead of external) and that actually worked.

so right now it appears to be the power extension cable or my external power socket is providing 'noisy' electricity 🙂

Will have to investigate further with more A/B testing