Scope tracking just drops out randomly - Sitech/Mesu/SGP

[kirkster501]

Yet another problem I am having but this is much weirder and difficult to fathom.  Not having a good time of AP this last two clear nights we have had.  Feel I really have taken up arms against a sea of troubles, to borrow a phrase from Bill....

Last night I got two perfect ten min subs of M13.  All going great.  Guiding great.  Polar alignment is spot on.  Balance is good as I can tell with a MESU.  Pride comes before a fall don't they say?  Then the centering of the subject just drops away and drifts.  Mount is still running but subject just drifts off until it eventuality leaves the field of view..... Also, notice that the Sitech pop up window where it states "tracking" sometimes just stops but not always.  And I cannot press the start button again without slewing away from the subject.  Then it will allow me to press start again.  I am on latest 91t version of Sitech so that would not appear to  be the issue.  We are miles past the meridian flip so that is also not the cause.

You can see this in PHD.  Guide star just drifts away, implying the mount has changed speed or stopped.

All is well initially.....

 

I cannot understand what could cause the mount to stop or change speed after just doingh 2 x 10 min subs!   Here are my SGP settings:

Appreciate any ideas please!!!!!

Is there any way to start Sitech tracking immediately, without having to press "start"

Thanks, Steve

[gnomus]

This is all very odd Steve.  I usually plate solve to a target at the start of the sequence.  That first 'Offset Init' then starts the mount tracking and I can forget about it.  

A couple of things stick out rom your screenshots.  Firstly, you don't seem to have a PXP model loaded.  That is probably a red-herring since I don't think you need to have one, but if you have made one, why is it not there?

The second thing is that your Sitech window is showing 'Guide'.  I am fairly sure mine says 'Slew', but I won't be able to check until tonight.  

I would suggest doing screencaptures of all of the tabs in Sitech.  I could then compare what you have to what I have - if that would be helpful.

Steve

[PhotoGav]

I am stabbing in the dark (as per most clear nights in my Man Dome) as I don't know the Mesu system, but I did have a similar problem with my HEQ5 a while ago where the guide star would just start drifting off screen. I narrowed it down to a dodgy connection with the South guide pulse coming from my guide camera. An out-patient appointment for the guide cam with StarlightXpress and a new output connector fixed this and it now works (damn, I've just cursed my whole set-up, and it all worked so nicely last night...).

As I say, might be of no help whatsoever, but thought I would add my experiences to the conversation. I hope you suss it out quickly.

[PhotoGav]

Forgot to add - I clicked the four guide directions in the manual guide screen of PHD2 to discover that all worked except for South.

[ollypenrice]

 

The guide trace shows the guider manfully trying to pull the RA back into the right place, succeeding just once and then continuing to try without success.

Assuming something is going wrong with the RA drive, I wonder why the guider had that one success in the middle of the trace? An intermittent fault? Power supply?

I'm not quite sure from your description what would happen if you took the guider out of the equation. Would the mount remain reasonably well centred or would it stop, or would it drift off while not actually stopping?

I'd want to eliminate the possibility that the guider is not doing what it says it's doing but is actually driving the mount off target due to some bug in the system. (I crossed with Gav but something on these lines was lying behind my thinking.)

Olly

[gnomus]

57 minutes ago, kirkster501 said:

...... We are miles past the meridian flip so that is also not the cause......

 

I cannot see any times on your screenshot Steve, but according to my Sky Safari, M13 crossed the Meridian at ~12:07AM.  My nautical dark started around midinight.  I see that you don't have Meridian flip set in SGP.  Are you certain you were well past the meridian? 

[gnomus]

And come to think of it, even if you were, if you don't have PHD set correctly it sends the pulses in the wrong (opposite) direction post flip - I had this happen to me when I had it set wrongly.   It is very easy to make the mistake of doing two 'corrections' in software which, of ocurse, cancel each other out.

[ollypenrice]

1 minute ago, gnomus said:

I cannot see any times on your screenshot Steve, but according to my Sky Safari, M13 crossed the Meridian at ~12:07AM.  My nautical dark started around midinight.  I see that you don't have Meridian flip set in SGP.  Are you certain you were well past the meridian? 

And are you certain that the software knows correctly where the meridian is? I don't know the SiTech so I don't know how it tells that the mount has arrived there.

 

[gnomus]

3 minutes ago, ollypenrice said:

And are you certain that the software knows correctly where the meridian is? I don't know the SiTech so I don't know how it tells that the mount has arrived there.

 

Olly, Sitech comes with a reasonable (though crude) planetarium application.  It should know where it is if it has been 'Offset Init'ed'.  The planetarium is also quite handy in setting the limits for tracking past the meridian and flips.  If nothing is set up for this, then I think the Mesu gets to the meridian and then stops.  (Does Argo Navis do this too?) 

[PhotoGav]

6 minutes ago, gnomus said:

I cannot see any times on your screenshot Steve, but according to my Sky Safari, M13 crossed the Meridian at ~12:07AM.  My nautical dark started around midinight.  I see that you don't have Meridian flip set in SGP.  Are you certain you were well past the meridian? 

Are you on to something here Steve? SGP also reports 18 minutes 42 seconds to the meridian in the "All is well initially" screen grab. So two 10 minute subs would time neatly with hitting the mount limits and tracking stopping......

[ollypenrice]

Just now, gnomus said:

Olly, Sitech comes with a reasonable (though crude) planetarium application.  It should know where it is if it has been 'Offset Init'ed'.  The planetarium is also quite handy in setting the limits for tracking past the meridian and flips.  If nothing is set up for this, then I think the Mesu gets to teh meridian and then stops.  (Does Argo Navis do this too?) 

No, Argo Navis lets the mount track past the Meridian until colllision, when the Mesu senses the overload and shuts down.

Like you, I can't help wondering if Steve's problems are not related to the Meridian settings, perhaps aided and abetted by the guider running the wrong way round as a result.

I'd love to know exactly what happens without the guider.

Olly

[gnomus]

Just now, ollypenrice said:

No, Argo Navis lets the mount track past the Meridian until colllision, when the Mesu senses the overload and shuts down....

Oh you are missing out then.  You get an entirely robotic female voice (I know that's the way you like 'em) telling you that your 'limit' has been reached.  It's quite an emotional experience.  

[kirkster501]

Thanks guys.

This also happened with other targets too so the Meridian has nothing to do with it I dont think.

Indeed Steve - the mount DID stop- when it hit the Meridian when imaging M13 last night.  It was all working perfectly before that.  But afterwards I could never get the rig to keep tracking ANY other object.  I slewed off to M51 - three hours past the Meridian and same issue  Same with Ring Nebula.   Plate solve all worked, centred up nice.  Then drifted off.

A thought entered my mind.  When I plate solved, did I tick correctly, Scope is pointing East or West?  Hmmmm,. got me thinking..

[kirkster501]

The time is all derived from the time on the PC right guys?  Is the time explicitly set anywhere else?  If so I have not done that......

[gnomus]

From the PC Steve.

[gnomus]

3 minutes ago, kirkster501 said:

....

A thought entered my mind.  When I plate solved, did I tick correctly, Scope is pointing East or West?  Hmmmm,. got me thinking..

In my experience, Sitech normally gets this right.

[kirkster501]

20 minutes ago, ollypenrice said:

 

The guide trace shows the guider manfully trying to pull the RA back into the right place, succeeding just once and then continuing to try without success.

Assuming something is going wrong with the RA drive, I wonder why the guider had that one success in the middle of the trace? An intermittent fault? Power supply?

I'm not quite sure from your description what would happen if you took the guider out of the equation. Would the mount remain reasonably well centred or would it stop, or would it drift off while not actually stopping?

I'd want to eliminate the possibility that the guider is not doing what it says it's doing but is actually driving the mount off target due to some bug in the system. (I crossed with Gav but something on these lines was lying behind my thinking.)

Olly

That guide trace is a wild one Olly whilst i was having problems.  When M13 10 min subs came in before the tracking problem started the subs were PERFECT.  The trace was bang on.  however, PHD did throw a warning up during those "good " subs about RA and pulse guiding and guiding may be ineffective or something along those lines.......

EDIT:  and I dismissed that warning because the graph seems great and all traces within 1 arc pixel

[PhotoGav]

Mmm, shame, hitting the meridian would have been a simple fix!

Have a play with the manual guide screen in PHD2 and check that the guide messages are getting through to the mount. Good thing is you can do that during the day. 

[kirkster501]

These are my advanced PHD tabs

[gnomus]

As I said earlier, I think the Sitech Tabs might be more helpful.

[kirkster501]

2 minutes ago, PhotoGav said:

Mmm, shame, hitting the meridian would have been a simple fix!

Have a play with the manual guide screen in PHD2 and check that the guide messages are getting through to the mount. Good thing is you can do that during the day. 

How to do that Gav please?

I gotta entertain a little one shortly so can have a look later.

This sounds like a possible IT problem like I discussed in another thread.

[gnomus]

15 minutes ago, kirkster501 said:

Thanks guys.

This also happened with other targets too so the Meridian has nothing to do with it I dont think.

Indeed Steve - the mount DID stop- when it hit the Meridian when imaging M13 last night.  It was all working perfectly before that.  But afterwards I could never get the rig to keep tracking ANY other object.  I slewed off to M51 - three hours past the Meridian and same issue  Same with Ring Nebula.   Plate solve all worked, centred up nice.  Then drifted off.

A thought entered my mind.  When I plate solved, did I tick correctly, Scope is pointing East or West?  Hmmmm,. got me thinking..

And were you trying to use PHD to guide on these targets?

[kirkster501]

My sitech screens

 

[gnomus]

M51 would have been past the meridian, M57 crossed quite late on was it also on the West?

[kirkster501]

3 minutes ago, gnomus said:

And were you trying to use PHD to guide on these targets?

Yes I did Steve, no difference at all to what i was doing.  After I hit the Meridean, after that it all went pear shaped.....