Astrotrac lost its tracking ability..?

[stan26]

Hi Guys, I'm tearing my hair out with this!

My astrotrac has always been very accurate with 5min + subs not a problem at 200mm, but over the last few sessions I haven't been able to get rid of star trailing.

It has a fully charged 12 car battery so I don't think its a power issue.

I have it bolted to my wedge which is very sturdy and very accurately adjustable and proved to be great the first few times I used it.

Now I seem to get trailing (very elongated stars) in the RA axis. I have spent hours trying to drift align the wedge but still can't get rid of the trailing.

For example I start my drift align on a southern star, it drifts up and right indicating a north drift. I adjust and az bolts and the the north drift reduces nicely but im still getting east - west drift. I get to the point where I slightly over adjust so I start getting south drift so I back it off so that I'm now not getting any north/south drift on a southern star BUT its still trailing east west. I try aligning the north south misalignment on a western horizon star with the exact same results, i always manage to dial out the north south drift but never the RA axis east west drift if that makes sense...?

Am I doing something wrong..? Could there be something really obvious I have over looked...?

Cheers

Stan     

[Peter Drew]

With respect, you have'nt accidentally activated one of the other drive setting options, have you?. 

[StuartJPP]

Just a couple of suggestions...(please don't take these as condescending!)

Are you flipping the arm down for the Northern hemisphere? I messed up recently when I flipped it down to the southern hemisphere whilst standing behind the mount and got it mixed up

Are you powering up with no buttons pressed? I.e. lunar or solar mode?

Is everything well balanced?

Have you got any other power source? Always good to eliminate potential problems rather than think it is okay. Or a multimeter to confirm if you have got one. Could the battery be getting cold, lead acids don't particularly like the cold. An insulated box can help.

Does the tracking sound laboured? I.e. straining to move? I have cleaned mine of grease and muck a couple of times and then re-greased it. You can get the arm to move fast forwards by holding down the "play" button whilst powering-up then press the "play" button again to get to the start position then "play" again to wind fully. Rewind to return back to home. I use some cloth to remove the crud and then re-grease with a lithium grease.

Run the mount fully (re-power if you have done the above) and time how long it takes to get to the end stop, mine takes basically 01:50:00 before the initial beeps come in, then another 10 minutes of beeping. If yours is wildly different something with the internal clocks could be at fault especially if it is running too fast. If it is running too slow it could be friction of some sort.

Try winding it on for an hour and try again, could identify something on the threaded bar.

Are you using any guiding (or is it the non-guided version in your sig?), do you ever guide? Remove anything from the RA guiding port if you are. Make sure there isn't any crud in there as shorting pins will cause RA to either speed up or slow down. Not the AG version...

I assume you bolt it to your wedge each time you use it? Could it be fastened a bit too tight and distorting/warping something? Are the 3 mounting bolts short enough so as not to foul against the rotating section? I noticed this was possible a while ago when using some different screws that were longer than the supplied ones, if you screw them in too far it can make contact with the other rotating part.

Can't think of anything else at the moment...hope you get it sorted.

[stan26]

Thanks for your replies folks, Stuart your last suggestion about the wedge bolts being too tight may be bang on, ever since I have been using the wedge I have had this issue, although it has got worse over the last few sessions. Think I'll look at this first....

Thanks

Stan.