PHD2 ASCOM calibration failure and poor guiding

[Kevin Wisdom]

Hello,

Lately I'm having issues calibrating my AVX mount in PHD2, via ASCOM. 

The guide star never seems to move enough, regardless of whatever setting changes I care to make in PHD2.

Some weeks ago, I started noticing my tracking was terrible, even with short subs, good balance, polar alignment and cable management.

I have made no hardware changes and my rig has previously worked without issue for many months/years.

Over the course of the past three days, I have tried:

Changing cables.

Changing the Autoguide rate in the handset (and PHD2) from 50 to 90%.

Turning the Anti-Backlash setting on and off.

Updating ASCOM platform from 6.5 to 6.6.

A spare laptop running a previous 100% stable build of PHD2.

Running ASCOM wirelessly, via Celestron SkyPortal WiFi adapter, without the cable and handset (Celestron CPWI).

Using a Shoestring Astronomy GPUSB adapter.

All without success (the same issue every time).

But when I switch to calibration and guiding via ST4 cable, everything works perfectly. Ultimately, I need ASCOM over ST4 for my automated imaging plans.

The mount is physically good order and under normal circumstances, autoguides great.

TBH, I'm now at my wit's end and don't know what to look at next.

Here is my log

https://openphdguiding.org/logs/dl/PHD2_logs_wrZW.zip

Many Thanks,

Kevin

[Wayne Hawley]

Calibration not moving far enough. Not sure if this may help. 

I use an LX200 Classic with a ZWO120MM doing the guiding. The USB for the guide camera uses the Starlight Xpress Trius Pro694 built in hub. When I start the system I always have to disconnect then reconnect the USB from the guide camera otherwise it says calibrating but does not move the scope. Once it has been disconnected and reconnected it calibrated just fine. 

There is no problem with PHD2 but evidently something in the USB system needs a reset, once the calibration has completed everything works fine for the rest of the session, no need to reset anything again. PHD2 works fine and has made a huge difference to the quality of the images from the old LX200. 

Regards

Wayne

Sent from my iPhone 0790 1212761

On 20 Jul 2022, at 12:00, Kevin Wisdom <mrkw...@gmail.com> wrote:

Hello,

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[Brian Valente]

Hi Kevin

there's not much data here to go on - your runs are very short. 

Mainly i see dec backlash as being a constraint to your guiding

Can you please do a baseline guiding run and get back to us with the results, that will help with better data

https://www.dropbox.com/s/zrf0au7jaisvt85/How%20to%20create%20a%20baseline%20for%20guiding%20results%20using%20OpenPHD2.pdf?dl=0

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[Kevin Wisdom]

Thanks all,

I aborted guiding during the first log as I could see my stars were awful. No point continuing, as my imaging plan was already worthless. All subsequent logs were diagnostic.

I'm in the UK, so clear nights for imaging, let alone testing are hard to come by. Can the guiding run be performed using ASCOM sky simulator? I have previously used this for fault finding.

I'm not sure how I can get a guiding run if I can't calibrate. Will using an old calibration suffice?

Kevin 

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[Brian Valente]

>>> Can the guiding run be performed using ASCOM sky simulator? I have previously used this for fault finding.

I feel you on the limited sky conditions, but no you can't use a simulator for this type of test. 

I can't speak to using an old calibration, are you referring to the analysis or for guiding? for analysis, what we really need to see is a calibration run followed by both guided and unguided output, preferably around 20-30 minutes

for guiding, it's hard to say. You mentioned your guiding had gotten worse recently, so it's unknown if (and probably unlikely that) the calibration is still valid. 

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[Bruce Waddington]

The last two logs you sent are useless because you were using the PHD2 simulated camera!  Here's what the manual says about that:

Bruce

[Kevin Wisdom]

Hi,

Point taken - I guess I'll wait a while for clear skies.

Kevin

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[Kevin Wisdom]

Hi,

Over the course of two nights, I've recently found a window in the weather to perform a test and imaging run.

I've read the troubleshooting guide, deleted my old and created a new guiding profile using the wizard (CWPI ASCOM).

Carefully balanced my rig, polar aligned and calibrated as the guide stated. 

Started guiding, ran the guiding assistant for 2-3 mins and applied the recommendations. Guided for about 25 minutes.

Again, i could immediately see guiding was terrible in dec, so I increased Max Dec duration from 2500 to 4000. This may have helped a little. I then packed up for the night.

I started a full imaging run the following night with the same settings, and could see DEC guiding misbehaving after dithers, so selected RA-only dithers in settings and resumed the imaging plan.

PHD also repeatedly reported "star lost" errors, even though the sky was perfectly clear, with an unobstructed view, but continued to guide seconds later. After monitoring guiding for a while, I left it running for the rest of the imaging plan.

Fast forward to checking my data today, and surprise surprise, I have another ruined imaging plan. Oblong stars and my target drifting from view, frame by frame. Viewing the log, I also have no idea why PHD log viewer reports such a huge polar alignment error, as Sharpcap told me i was with 4' or so of Pole.

Here are my logs from the past two nights.

https://openphdguiding.org/logs/dl/PHD2_logs_WKzW.zip

Regards,

Kevin

[Kevin Wisdom]

One thing which did strike me is PHD2 for one reason or another, reports my guide rate at 0.85x, when my mount seems to be set to 0.5x (as reported by both the handset and CWPI software).

No idea why this is, and I can't seem too change it within PHD2.

Regards,

Kevin

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[Brian Valente]

Hi Kevin

I think the foundation of your issues was you started with a bad calibration, which included numerous lost star events. This was your last calibration before you started guiding, you can see the unevenness of the points in both RA and especially DEC, and the big difference in the # of points.

I'm surprised uf PHD did not warn you about calibration problems. 

so this point all your fiddling with parameters didn't make any difference, and it won't in the future. I would venture a guess that your Dec has mechanical issues, possibly stiction. look at your guiding from this run, you can see PHD is sending Dec corrections which are ineffective until it snaps back in place:

You have a few variables here, so there are some things to try. First, you might want to use just the celestron ASCOM driver, or look at updating the CPWI software if available. There have been many reports over time of CPWI not performing correctly.

Second, you should focus on getting a good calibration,with evenly spaced points along both axis. This may require mechanical intervention on your mount, 

This should result in better guiding for you, but let's see how it goes

Brian

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[Brian Valente]

>>>No idea why this is, and I can't seem too change it within PHD2.

you don't change the guidespeed in PHD, it's ready only. It takes that information from the mount connection. So it may be set somewhere else incorrectly

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[Kevin Wisdom]

Hi,

Thanks for the response.

Yes calibration is all over the place, time and time again.

I have only recently switched over from the Celestron ASCOM driver, cable and handset to the latest CWPI build because of these issues. They started before CWPI, and haven't changed since.

I'd serviced the mount myself not too long ago, amongst other things adjusting the Dec worm and gearbox for backlash. I've done it many times before, but I guess I'll take a look over it for any possible issues.

Is it possible to adjust guide pulse rate independent of mount in the ASCOM driver settings itself? Maybe that is the issue (as I have two different values), before I start tearing the mount down again?

Many thanks,

Kevin

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[Brian Valente]

Hi Kevin

>>Is it possible to adjust guide pulse rate independent of mount in the ASCOM driver settings itself? Maybe that is the issue (as I have two different values), before I start tearing the mount down again?

your issue is not the guide pulses. if it were that simple you could just recheck your settings and rerun. the issue is they are extremely uneven, which suggests mechanical issues. 

did you have these problems with the ascom only driver? Definitely make sure you have the latest CPWI, as I mentioned before

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[Bruce Waddington]

Hi Kevin.  Your mount basically isn't pulse-guiding after a short period of time.  I think you left out the important bit of information that you had disabled the alert messages that say: " PulseGuide command to mount has failed - guiding is likely to be ineffective."  That's like ignoring the check engine light in your car and then being surprised when the engine seizes up. <g>

Starting at 23:03, your mount driver spent most of its time not being able to pulse-guide,  so you were pretty much running unguided.  In the attempt at  23:03:11.278, PHD2 issued a 'south' guide command of 71ms.  By 23:03:13.35, that command had still not completed.  So PHD2 timed out, issued the alert message, and tried to move ahead.  But since you suppressed those messages, you probably weren't aware of the problem.  This problem recurred throughout the night.

You should talk to Celestron support about this - I think it's between their ASCOM driver and the mount.

Regards,

Bruce

[Kevin Wisdom]

Hi, Bruce

To be honest, I've completely lost track of all the things I've tried, so it wouldn't surprise me at all if I've surpressed any PhD warnings.

As I've pretty much thrown the kitchen sink at this, I'm giving up troubleshooting this mount for now, and will likely take it in at a local reputable astro retailer for diagnosis.

Thanks for your help,

Kevin 

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