EQ3-2 tracking issues (not synscan)

[Chimer4]

Hi guys, first time posting here so I hope that I am presenting a valid question. I've tried looking online before posting but I can't find anything that matches my problem exactly do apologies if it has been answered

I'm currently using the EQ3-2 mount with the single axis RA motor for tracking. I can get pretty accurate with polar alignment as I can get frames with perfectly sharp and pinpoint stars on at least 1 minute exposures, however some come out terribly. In some the stars look like little dumbbells (2 dots with a thin line connecting them) or tadpoles. I know that I didn't touch the mount to cause this and my camera is running remotely with an intervalometer. It ruined my session the other night giving me only 5 viable frames out of 30.

Does anyone know what might be causing this and if so how to fix or minimize it? My guess is that something is slipping or sticking in either the motor or the mount.

Thanks for any replies

Will

[Stargazer33]

Hi Will, welcome to SGL! 

What is your mount sitting on? Are you moving about around the mount whilst the sequence is running? Are your mounts clutches tightened? 

Failing that it could be poorly meshing gears or even damaged gear teeth - periodic error.

[Chimer4]

Hi! 

I've got staked down into the grass and I've been sitting down about 4m away from the mount whilst it's been running. I went up to it every now and then to check it was still running (Sony F batteries) but not enough to ruin as many frames as I had. All clutches and screws are tightened down as much as they can be.

I hope it isn't damaged gear teeth, I haven't even had the mount a month yet. I've heard things about the grease they use not being great, could that contribute to it?

[Chimer4]

Just a follow up to this, in case anyone comes across this.

After taking apart the housing block on the RA axis, it seemed as though the worm gear was tightened too much onto the ring gear causing stiction and slight binding. The grease wasn't too bad, but I spread it around a little better (there were 2 huge globs at the ends of the worm gear rod, not actually in the teeth) and spread a little of it into the bearing in the housing block for the rod. I might re-grease it at some point with some better stuff, but it seems ok for now.

When I reassembled I tightened the 2 long bolts down nice and tight and played around with the 2 shorter bolts and set screw until I got a nice smooth action an without any noticeable backlash (not that it matters a great deal for me, I'm not doing auto guiding)

I can now smoothly spin the fine control knob and it feels greatly improved. I also filed down the screw holding the motor sleeve onto the worm rod to make sure it got a nice positive grab to reduce any play there.

I'll update this post once we have a clear night and I'm able to see if this has made any real difference to the issues I was having, but by the feel of things compared to how they were, I have a good feeling that they will

Will