Troubleshooting tracking issues on an EQ6

[Chancellor]

Good morning
A few nights ago I started having some issues with tracking / guiding on my mount. On occasion the scope would jump around slightly and PHD would drop the guide star temporarily. From what I noticed this would occur every few minutes making long exposures impossible.

The setup is an EQ6 Pro with an ED100. Guiding is done via a Orion Starshoot autoguider and PHD through a ST80. So there is nothing special here.

The mount was setup to a 5 minute drift alignment, so I am pretty sure that drift would not be the problem.

I also checked that everything was balanced but still had the same problem after adjusting slightly.

I have included a sample frame and a sample screenshot of the PHD graph while the frame was being exposed. (Please ignore the focus and colour)


The following link also shows a sample of the debug log from PHD if it's of any use. I have done some quick graphs of the data in excel and there definitely looks to be a pattern. Beyond that I don't know exactly what I'm looking at.
http://completelyserious.com/pics/mountts/PHD_log_30Dec10.txt

Basically, I'd like to know what could cause this?
I am tending towards a problem with one of the gears though before opening up the mount I'd like to hear what others can suggest.

Thank you for any info you can provide.

[wasyoungonce]

I am thinking that the mount tripod has been bumped or walking near it has induced vibrations causing it to loose track..or maybe breeze? I say this because RA & DEC all of a sudden both have hernias!

What base is the tripod on? You said your drift align was fine...if the issue had been present then you would have seen this during the drift align.

Also maybe lower RA aggressiveness a little and check your ST4 correction rate is lets say .5 sidereal. Check all nuts bolts and plates are tight..as well as focuser tubes.

I had similar issues last night...I had a cord wrapped around the tripod getting stuck...it's the little things that cause grief!

[Astroman]

Early EQ6's sometimes had grit or small shavings caught up in the gearing, which would cause erratic movement or jumping. You may have something either in the spur gears or on the worm it'self. If the mount is out of guarantee, open it up and check the gears. If it's still covered get the place where you bought it from to do a check.

[Chancellor]

Thank you for your replies.

I was wondering about both the RA and DEC moving so quickly, which is also why I came here :)
I'm sure that the mount was not being bumped or touched in any way, and while there MIGHT have been a slight breeze, I was in a relatively sheltered area so I doubt that would have been a problem.

I did check the nuts and bolts, and the mount is on some large pavers so not going to sink into the ground any time soon.

I am thinking tonight I'll just do a few tracked subs with no guiding and see how that goes. At least it rules out something to do with the guiding system going crazy.

The mount is still under guarantee, however I'm still a little tempted to open it up anyway to do some cleaning. (It always sounded a little grindy compared to some others)

I have a few new ideas though, so thanks again for your replies.