AZEQ6 tracking issue

[almcl]

I had a thread about drift in RA a little while back but have had no opportunities since to put the several  suggestions offered then to the test.  

Two nights ago the cloud rolled away for a while and although I haven’t completely solved the problem, I may be a bit closer to understanding a possible cause.  

I noticed that when slewing the AZEQ6, always finishing up with “up, right” as per manufacturer’s instructions, the tracking doesn’t always restart and the target star doesn’t stay centred on the cross hairs but sets off along the left/right axis.  Not yet certain but it seems as if the RA motor either doesn’t restart after the slew or stays at slew speed.  

I am not yet sure if this only happens when using, or after using, the gamepad or with both pad and the EQMOD control buttons, but I wonder if anyone else has experienced anything like this?

The other question is (assuming the theory above is correct) how to stop/prevent/correct it? I had some success the other night at arresting the unwanted star motion by briefly clicking the opposite direction button on the control, but feel there ought to be a better solution.

[jambouk]

Is the mount tracking at all? Is tracking to sidereal rate turned on? You can test this in day time by pointing the scope at a static feature on the horizon (or a neighbours chimney) and just review the view through the eye piece in 5 minutes and see if it's moved.

Is the kit well balanced?

Is there a lot of backlash?

Although we all say "up and right" you should do your last movements in the same direction that the mount does it last movements - depending on your scope this might be "left and down", just watch what it does when doing the fine centring next time.

James

 

[almcl]

21 minutes ago, jambouk said:

Is the mount tracking at all? Is tracking to sidereal rate turned on? 

Is the kit well balanced?

Is there a lot of backlash?

 

That's a 'yes' to all three, I am afraid, James.  

There's quite a bit of backlash, although PHD2 seems to have no trouble taking it out and, once  a 3 star align has been completed, the gotos are usually pretty good and if no operator interference is required for framing tracking is usually (but not invarably) OK.

I'll have a look at how the mount centres itself, thanks for the tip, but I think it's as mentioned on page 15 of the Synscan manual, although of course, when guiding, the Synscan handset is not connected (EQDIRECT cable from laptop to mount) and EQMOD may have different approach...

. 

[Mark_C]

After looking at your previous thread, I can say that I suffered this exact same issue, and experienced the exactly the same images as you have shown. I found that the problem was both a combination of flexure of the finder guider and play in the mount.

I have the same mount as you and found that when both axes were locked down, there would be a slight 'rocking' of the mount, this was enough for the mount to move ever so slightly during guiding and cause all kinds of issues. This could be contributing to the severe backlash you are experiencing.

Have you tweaked your DEC and RA set screws for your AZ-EQ6? This should position the gear against the worm more snugly so that backlash is considerably reduced. With regards to the finder, I found that locking the ring screws down as much as possible reduced flexure to a minimum, mine were not entirely tightened which contributed to flexure and therefore contributed to incorrect guiding relative to the imaging scope.

[almcl]

I've certainly noticed the rocking you mention, Mark, but haven't had the courage to tighten the worm drives so far.  

Experiments have been slightly curtailed by cloud but also by a new (2nd hand refurbished) Laptop which has required a vast amount of installation of software.  

That and solid cloud cover, of course.

[Mark_C]

13 hours ago, almcl said:

I've certainly noticed the rocking you mention, Mark, but haven't had the courage to tighten the worm drives so far.  

Experiments have been slightly curtailed by cloud but also by a new (2nd hand refurbished) Laptop which has required a vast amount of installation of software.  

That and solid cloud cover, of course.

Yes, I know what you mean. I was also reluctant to make any modifications, particularly as the mount was new at the time, however I found it did make quite a difference. It's not all that bad though, it doesn't require opening up the mount so is relatively low risk.

Having said that, it may also help sometime in the future to open the mount up and clean the worm and gears of the factory installed grease, as this has been known to contain bits of swarf that can cause PE. I don't think the grease Synta use is that good either, particularly in cold weather when it is likely to stiffen, which is certainly not going to help with tracking. 

I will admit that dismantling and reassembly of this mount is quite a daunting task and not for the faint hearted, so it may be best left in the hands of someone who does this on a regular basis!