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Old 07-02-2016, 10:35 AM
bugeater (Marty)
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RA axis binding?

I've just setup my equipment (AZ EQ6) on a pier in my new observatory and are getting things running. But I seem to have hit a few problems, the most perplexing is the one in the image attached. It looks like the RA axis binding, but I'm open to other possibilities. It does as in the picture and you can see the star images moving in the guidecam image, then it usually stabilises again.

I haven't used the setup much for months and did have some strange stuff happen last year with it not tracking properly. I played around with the worm mesh, but only on the dec axis (if I recall).

If someone has seen this before or has any thoughts, I'd like to hear it. I'm probably going to get in there and see if I can adjust the worm mesh (which is a bit of a confusing process I've found).
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Old 07-02-2016, 10:43 AM
kens (Ken)
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Maybe you are getting too close to/beyond the meridian so the limiter is kicking in to stop tracking.
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Old 07-02-2016, 11:51 AM
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codemonkey (Lee)
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How does the mount sound when this happens?
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Old 07-02-2016, 12:19 PM
bugeater (Marty)
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No it's not limits. Eqmod doesn't say limit reached or anything like that and tracking continues.

It does sound a bit... funny when it happens, but I'm not sure if that is just PHD trying to throw in a lot of corrections quickly. But it isn't an obvious stall.

Anyway, I've loosened off that axis so it now has a bit of play in it. As it turns out the worm float adjustment is much harder to access on the RA axis as there is an encoder held in by fiddly little screws in a confined space. What a nightmare. I backed it off a little just in case.

I also thought to adjust the belt tension, but as it turns out, the screws I thought did this don't seem to. Or at least not obviously. Not sure what they do actually... The attached pic shows where I circled the bolts I loosened off for the stepper motor. I thought the grub screw on the left went all the way through to the motor, but it doesn't seem to. Anyone know what the arrowed grub screws do/how they work?
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Old 07-02-2016, 02:33 PM
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Atmos (Colin)
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My EQ6 Pro did exactly the same thing last night in PHD2 as well! I got the feeling that it was a software issue more so than mechanical as when I ran the first few minutes in the guiding assistant part, had no issues. When guiding however it did it twice in a row, it wasn't binding as after a minute or so the guide camera had shown significant drift. My first thought was backlash but it didn't go away and as it was actually moving (could see the drift from frame to frame in the guider), I figured something strange was going on.

Gave up with PHD after 10 minutes, started MaximDL purely for guiding and got round stars with 900s subs with a RMS of 0.35. So, my impression is PHZs playing up last night.
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Old 07-02-2016, 03:50 PM
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codemonkey (Lee)
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I had a similar thing recently with my EQ6, dropping up to 40" at seemingly random intervals, also using PHD. When mine did it, it would sound like the mount stopped tracking for about a second before kicking back in. I didn't get to the bottom of it because I decided I'd have enough with the EQ6 and bought a new mount. I'll eventually get around to fixing it, whether to sell or to keep as a backup, so I'll be watching this thread closely.

I'd assumed my issues might have been electrical in origin. I checked the voltage output of my battery which was fine, watched the power light on the EQ6 while it stopped tracking and saw no flash/dim of the light.

I don't have the AZ-EQ6 so I'm not sure about the bolts. Top three could be to hold the motor's frame, bottom two could be to hold the worm casing...
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Old 07-02-2016, 05:56 PM
tim.stephens (Tim)
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I've had the same issues on and off for a few weeks now. Seems to have been reduced with a gear mesh adjustment but has never completely gone away.

I currently have plenty of slop on my RA and have to balance carefully to ensure proper gear meshing. The solution for me is to watch PHD like a hawk, and if it happens, slew East slightly then back to the target to resume imaging. Very very annoying. One week during the winter, I'll do a full RA strip and regrease, and perhaps the belt mod upgrade too.

One has to wonder if we are throwing good money (and time) after bad and a new mount is the real solution? Perhaps better the devil you know!

Tim
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Old 07-02-2016, 10:41 PM
bugeater (Marty)
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Well at least I'm not alone with this irritating issue. But joy, I may have found the problem.

I've been experimenting and I think I can confirm the following:

  • It is specific to the RA axis (reproduced the effect with slewing and turning off tracking).
  • It does it in both directions (it isn't just the axis stalling, it will sometimes go the other way) - important observation.
The attached chart shows five of these "events". On the first three it completely lost the star and I chose another one (so while it looks like it got the star back, it didn't). Note the "effect" goes in both directions. On the forth, PHD fought and managed to get back tracking. I stopped on the fifth and last event. The mount was pointed for drift aligning (pointed at the zenith? and meridian I guess).



What this suggests to me is that it is not a stall. It doesn't sound like one and a stall couldn't actually actively slew the axis, which seems to be happening sometimes.


This leaves software or electrical problems. I've rebooted and still got one of the events. I also looked at the Eqmod log and saw nothing being sent except the correction from PHD.



But I also finally rerouted the shoestring cable thing away from everything else electrical and gave it its own USB port (not through the hub). I'm currently looking at the computer in the observatory (Teamviewer is quite good...) and its been running for nearly 20 minutes and there hasn't been one event! So it seems to be electrical interference on the shoestring cable.

Of course a bit early to call it definitively, but definitely promising.
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Old 07-02-2016, 11:05 PM
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Atmos (Colin)
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That is some good trouble shooting there, I pretty quickly figured it wasn't mechanical because although it was acting like it was a backlash error (sending a lot of pulses but unable to recover) the mount was responding (could see it slowly drift a degree over two minutes or so) so instantly figured it was software related. This was this backed up by MaximDL guiding with no issues over a two hour period. Thinking back, it seems like it got the East/West direction around the wrong way for whatever reason. If it keeps sending pulses in the wrong direction it will just keep sending them.

Anyway, glad you've got it working again
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Old 08-02-2016, 05:59 PM
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ZeroID (Brent)
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Wonder if that is the cause of my problem. I just stripped the EQ6 DEC axis down for something similar. It all seemed ok inside but I washed it all out and relubed it anyway. I wanted to do the RA but couldn't undo the round 'nut' on the shaft. But if it was in as good a state as the DEC it shouldn't need it. Soon find out when the clouds go away.
Thanks for the info, the rebuild also meant I changed wiring layout so we'll see.
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Old 13-02-2016, 12:18 PM
bugeater (Marty)
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Given the unprecedented run of clear nights lately + new moon, I've been running my gear every night and the problem hasn't come back. So unless it's somehow related to the orientation of the mount, it seems cable interference was the issue. Good lesson to learn now rather than later I guess.

Now I just need to go back in and remove the axis play I introduced...
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Old 13-02-2016, 12:41 PM
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codemonkey (Lee)
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Glad to hear you sorted your issue out, Marty! Good luck with the meshing... that's always a PITA.
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