Should I replace all the bearings in my HEQ5 Pro?

Hi Andy,

What do you mean by "stars are still a bit affected"?
Personally, I would leave the mount as it is if it does a good sub arcsec guiding. Depending on what "sticky" specifically means in your mount's case, a bit of "stickyness" can be better than a completely frictionless bearing.

Björn

I‘d do a partial hypertune, what is definitely a good thing is to replace the small bearings that hold the worm-gears. Mine were of horrible quality, you could feel that something was wrong with them.
Easiest way to test is to either remove the gear in the middle or, if you already have belts, then remove the belts and manually turn the wormdrive gear of ra + Dec. My RA ran fine, but on Dec I could clearly feel when turning that things were not smooth. Turning the gears manually is also in my point of view the best way to later adjust the distance between the worm and the gear, it is easy to feel when turning if you are too tight or just right.


It is also easy to replace the V shaped bearings in RA and DEC. Replacing the big bearings can be painful, I only replaced two of them and I saw in several hypertune reports that they are the least important to replace.

The stiffness can also be caused by the mount´s bearings beeing tightened up too much, Check Astrobabies Page https://www.astro-baby.com/astrobaby/ there is more information on that in the Tuning section for the HEQ-5

Overall, the Hypertune did not make as much difference as the belt mod for me, but my mount was fairly new, so besides the wormgear bearings there was no real issue but in the process the stiffness of the axes went away so it is now a lot easier to balance the mount.

Michael

Please update us with what you do

I will do ... bearings and lube have been ordered and should arrive within 4 days.  I'll post the results as soon as I can

OK, DEC axis stripped down, cleaned and re-lubed.  Small bearings on worm gear were not good, however all the others seemed fine.  Main bearings arrive 2moro, so will get the DEC and RA axes done then.

FWIW:  It's a fairly straightforward process so far.

It's a really cheap upgrade to replace all the bearings and I can't see how it would make it any worse

I had it from a very reliable source that bearings quality isn't that important past a minimum threshold. IOW, if they feel fine don't touch 'em. I do however sympathize with the urge to replace things old with new and the satisfaction that comes from putting everything back together. Good luck!

The other really satisfying thing is getting to know your mount and how it works.  They are actually very simple mechanisms (a couple of motors, two worm gears, a bunch of bearings and a control board) that could do with regular maintenance to keep them at their best.  It's a lot simpler than my 3D printer.

Although I'm replacing all the bearings with better ones because the total cost is only about £70, I actually think that the only ones that needed replacing were the little ones on the worm carriers ... total cost for those was £20 for four of them.

Andy Wray:
One of the main ones was so stuck on the DEC shaft that I had no way of removing it.

Maybe is too late for this but, unless you have a bearing extractor, the way to handle this issue is to put the casing on the gas hob (or use one of those hot air guns) to heat it up and while (very!) hot hammer out the bearing. The difference in thermal expansion coefficient between steel and alumnium is large enough for this to work even at moderate temperatures (say 200 degC).

OK:  the good news is that I don't appear to have broken my mount by replacing all the bearings.  I've got it imaging tonight and it seems to be guiding slightly better than before the upgrade.  Currently at 0.6 arc secs guiding RMS average.  That's not much of an improvement, however two things seem to have improved:

1) The DEC and RA are about the same now which should give me rounder stars
2) The number of corrections being sent to the mount are far fewer
3) When I look at the PHD2 scatter diagram it is much rounder than before

Fingers crossed, this was worth it.

andrea tasselli:
Hi Andy,

Can you post a PE graphs of the before and after?  That would be instructive...

That would be great. 

I also use an HEQ5 and upgraded with the Rowan kit and adjusted the worms. 
The astrobaby link that Mike suggested in an earlier post greatly reduced my DEC friction.

My overall total rms error is at worst about 0.8 arcsec/px.
I also get higher RA error than DEC especially when imaging near the CE, but the RA and DEC error are close when imaging more northern targets with an overall total rms error around 0.4-0.5.
Thanks for sharing this Andy. Just relaying my experience.

Jim

OK, the clouds cleared for a bit so I am imaging tonight.  After 1.5 hours my guiding is as follows:

* Total RMS is varying betwen 0.63 and 0.72 arc secs
* DEC and RA values are between 0.42 and 0.5 arc secs
* DEC and RA values are broadly equal at any one time which means round stars throughout

Graphs will follow.

N.B.  I'm running an 8" Newtonian + camera, filter wheels, guiding cam, coma corrector, autofocusser etc. weighing 11KG in total on the HEQ5 Pro.  I'm probably at the HEQ5 Pro limit for imaging to be honest.  I will tune PHD2 some more and can hopefully get to 0.55 arc secs, but I can't see it getting any lower than that.

OK, bottom line is that I would highly recommend the gear replacement in an HEQ5 Pro that is 3+ years old.  Over quite a few nights now I have noticed:

* PHD2 calibration works well at any sensible altitude
* Guiding is reliably between 0.55 arc secs and 0.7 RMS for clear skies or skies with whispy clouds
* RA and DEC are much closer to each other now in terms of RMS, so my stars are a lot rounder
* I'm actually not throwing away any subs due to tracking issues

I could probably try and tune it further, but with my seeing conditions and my heavy load on the mount I'm going to leave it well alone.

Here's a typical guiding session with some whispy clouds passing by (see star intensity drops):

Beautiful guiding results Andy! 

Thanks for the graph too.

if you don’t mind me asking, what was your target?

Thanks, Jim

In this case it was M51 if that is what you meant by target.  If you meant what target RMS guiding I was aiming for then it was 0.55 arc secs which I do achieve now when the sky is as crystal clear as it can get in my suburban area.

I think I could improve things by focussing my OAG better, tuning out any residual backlash and tweaking PHD2 settings, however that can wait for now as it's "good enough" and the skies are clear so I just want to be imaging right now.

Would you mind listing their part#'s.

Here you go: