PHD2 Cannot Make Sufficient Corrections in DEC

[Kurt Lanes]

I am trying to understand this error that crops up when I am not looking. Usually this is a problem with a cable snag but I am pretty sure that isn't the case here. Looking the next day I see a bunch of star streaks that are really a bunch of dots. These are aligned in DEC so it tells me that PHD2 is sending corrections and the mount is acting on them. To troubleshoot this I measured the performance of my L350 and it leaves a lot to be improved but tracking looks great in RA but has a 0.045"/second drift in DEC. I was running at 15 seconds integration in PHD2 so that gives me an error of about 0.67". My aggressiveness is set a at 0.7 so my first thought that the corrections are not big enough doesn't sound right to me but at the same time makes the most sense form the results I am  seeing. Any help is appreciated.

Kurt

[Bruce Waddington]

We can't help you with this without seeing the data:

https://openphdguiding.org/getting-help/

Bruce

[Kurt Lanes]

Sorry Here is the log 

[Bruce Waddington]

Please read and follow the instructions using the link I sent you.  We need to see both the guide and debug log files from the session.  Just use the built-in Upload Logs feature in PHD2.

https://openphdguiding.org/getting-help/

Bruce

[Kurt Lanes]

Here is the link. https://openphdguiding.org/logs/dl/PHD2_logs_y5Bu.zip

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[Bruce Waddington]

Before we get deeper into this, can you provide a little more background?  It's unusual to see someone using a long refractor on this mount.  Is this just one of two scopes on the mount?  Can we assume you are running on a wedge?  Is there a rotator associated with the refractor?

I looks to me like there are a bunch of problems here, both with the mount itself and many other operational things.  I just don't want to spend a lot of time on all of that without knowing for sure what your configuration actually looks like.

Regards,

Bruce

[Bruce Waddington]

One other thing I forgot to mention - the debug log file you uploaded looks like it's been truncated at the front, it doesn't represent the full log.  Please don't do that, we need to see *all* of the data and I'm missing quite a bit of that in your case.  That's one of many reasons we provide the log uploader facility, there is no need to worry about file size constraints.

[Kurt Lanes]

Bruce

I do have two scopes on the mount with the wedge. I have a TEC140FL at 862mm and a TAK Epsilon 160ED at 532mm. I bought the L350 with a CDK12.5 but I traded that because the seeing here is around 3” and the CDK was too long for that. I am interested in why this is unusual.

IDK what the issue is with the truncation I didn’t thought the logs just clicked the upload.

I think I am on to the problem. I checked the Polar alignment and it was off by 15’. This is a permanent installation so I don’t know how that happened but then again I haven’t checked it in months. I did a realignment and updated the PHD2 calibration but I had forgot that I zeroed the aggressiveness so I didn’t get a test of the tracking. I will do the final model update tonight but my theory is that PHD2 was just not able to keep up with that much polar error.

Thanks

Kurt

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[Bruce Waddington]

I'm not saying anything is wrong with using your two refractors on the mount, I'm only saying I haven't seen that configuration before.  Usually we're looking at heavy but compact telescopes such as the CDK design.  As you probably know, these mounts are quite sensitive to balance, need to be "tuned",  and are also sensitive to wind.  So I don't know how that will affect a setup like yours where there are two scopes with distributed weight loads.  In any case, I don't really follow your preoccupation with the Dec performance.  At least in the log for your 8/28 session, both axes performed equally poorly.  Here are two examples, both with RA in red and Dec in green:

This sort of thing is not at all what we expect from a high-end mount with absolute encoders.  It has nothing to do with polar alignment error, there is something mechanically wrong with the setup.  If you think the PA has suddenly changed, that may be because something on your rig has loosened up which could also affect your tracking performance.  The top graph shows a long period of very poor tracking which suddenly stabilizes on its own.  This is a common symptom when the underlying problem is cable routing or something else that is interfering with the smooth tracking of the guide camera.  In these graphs, the sudden "return to zero" is a consequence of losing the guide star, something that is happening much too frequently for you.  Of course, when you get huge guide star excursions like the 20-30 arc-sec we see here, the original primary guide star will probably be lost and you will be trying to guide on whatever happens to be inside the tracking region.  I noticed that you had disabled the alert messages for situations when PHD2 can't correct adequately for RA.  That may have led you to believe that Dec was your only problem - not the case.  Disabling alerts like this doesn't usually make much sense, the problems are real and the result with be poor until they are corrected.

With regard to the edited debug log file, my guess is that you originally edited the file in order to attach it to your forum message, at which point the original data are lost.  It doesn't matter, but please don't modify the log files in any way if you need to submit them to get help.

Hope you can track down these problems quickly,

Bruce