AZ-EQ6 driving off on its own while guiding


I am having issues with my AZ-EQ6 mount.

While guiding, it seems to want to move off in one direction on its own, with no command being sent that I’m aware of at the same time as ruining a good exposure, some times two or three in a row.

I’ve had the guys at PHD2 look at my logs with no explanation available either.

I’ve tried to back off the drives in case of binding at the risk of poor guiding and backlash and it still exists.

I am using EQMOD with a Shoestring cable and I have encoders swithched off.

I am thinking of going to the Synscan app and pulling the board out and disconnecting the encoders as I’ve heard they can cause issues.

Any SGP’ers aware of this issue or may be able to provide an explanation?

Thanks in advance.


I have had similar issues with the EQ8. (Read a previous post)

How much does it move over time? I have drift in the original coordinates I have set after each sub.

I read in the fits headers, the RA and Dec coordinates, after each sub and they are different.
Is this normal? I thought once you set the RA and DEC it should be the same.
Except for small dithers, which, I set at 2 pixels every 5 frames.

After an hour, I will have to re-centre the object. I keep thinking it’s poor polar alignment.
I may get to talk to someone from Skywatcher at a Star Party this new moon.



It is worth repeating that the encoders for the EQ8 should be turned off. Corrosion/damage to the encoder wheel (they are essentially exposed to the environment) can prompt the mount to make corrections that are not warranted. This can also explain drift. It was an issue for me at least (and many others). Not sure if it is the same for the EQ6.

In fact I am having an issue now with some drift and I’m wondering if the encoders are actually on even though EQMOD tick box says they are disabled (balance and PA otherwise seems good, so looking for another explanation).



Thanks for replying.

I do not have drift, I have a sudden spike in movement as if someone has pushed a direction key for 5 seconds, up to 30 or 40 pixels sometimes, enough to loose the guide star and not be able to restart the sequence that has subsequently become cancelled (not an SGP issue).

I have pulled the board and disconnected the encoders from the board however I have not had enough time to test if this has made a difference as it can be a bit intermittent.

I’ll get back as to how it works out.


Yes - sudden “spike” (sometime resulting in loooong star trails) can be explained by encoders as well. Let us know how you get on with it.



Thanks to those who responded, I appreciate that.

I first disconnected the encoders from the main board and left the drive backlash as is and it seemed to have made a difference with no runaways although the guiding was pretty bad, to be expected I suppose.

I then returned to the obs and adjusted the drives back to nice mesh and while I was at it I spent some time re-balancing. I have now got very good guiding with seemingly no runaway although there is still a bit of DEC backlash, mostly which PHD seems to be taking care of quite well.

I don’t know how much tighter I can make my DEC before it binds to clear that backlash, it is so tight/close/backlash free checking it by hand I do not want to adjust it any more. The mount sounds so sweet when driving at full speed and guiding is pretty good except for the backlash pulses

Summary, at this stage I am going to blame the encoders.