PHD2 Reporting cable snag but nothing appeared wrong

[IDM]

Hi

 I have been using PHD2 happily for about a year but recently have had it causing issues and stop working reporting possible cable snag or unable to move mount.

The setup is a Zwo ASI120M connected to telescope PC via USB cable and SW EQ6R mount also connected to telescope PC. The mount uses Ascom to connect and works fine with Stellarium and can move and plate solve with Sharpcap pro but I get the issue with PHD2.

Initially I found the problem when photographing the Heart Nebula which was nearly vertically above the scope. However, after the failure I thought maybe it was my calibration so I slew the mount to a star nearer the horizon, deleted my calibration and tried to recalibrate. The process started and then failed with PHD2 reporting it was unable to move the mount.

I have attached the guide log. It was so annoying as last night was possibly one of the clearest nights I have had this autumn and in the end I could do nothing but take down the telescope and give up on the night.

Does anyone have any ideas?

Thanks,

Ian

PHD2_GuideLog_2022-11-20_205724.txt

[900SL]

Have you tried swapping cables? I had an issue with ASI Air Pro drift that turned out to be a intermittent cable fault. 

[Clarkey]

Looking through the guidelog, I would agree with @900SL that changing the cable would be a good starting point. Initially the guide commands were working OK, but for some reason just stopped. This suggests a mechanical or electrical issue rather than software or drivers. Did you try slewing from the PC to see if the mount was responding from any other software?

On a separate point, you might want to increase your guiding exposure slightly. At 1s you are likely to be 'chasing the seeing'. Probably 2 - 3 seconds would be better.

Edited November 22, 2022 by Clarkey

[ONIKKINEN]

I dont think a cable snag alone explains why your mount completely stopped responding to guide impulses. It looks like something mechanical has completely jammed/gotten loose with how all impulses are ignored. Could also be a software issue of course, i had a case when EQMOD had put my mount in some weird slow slew mode for some reason and PHD2 stopped issuing guide commands as it found the mount did not respond to them. Might be worth it to go over all the different software involved and recheck the settings.

Other than that check for mechanical things like the tripod sinking as you have about a degree of polar alignment error at the time when the issue begins. Also check your clutch, it can easily be too loose with the EQ6 causing motor slipping which would also appear as the mount not listening to commands. If you can easily move the scope while your clutches are locked, the motors will slip a little bit, and could slip completely.

[michael8554]

Hi Ian

The message "RA Calibration Failed: star did not move enough"

Is because you have your guide rates set very low:

RA Guide Speed = 1.5 a-s/s, Dec Guide Speed = 1.5 a-s/s

This is probably because you have the EQMOD "ASCOM PulseGuide setting" on the default value.

Guide speed needs to be at least 7.5 a-s/s.

MultiStar guiding is a way to compensate for "Chasing the Seeing".

So Exposure = 1000 ms is probably okay.

Michael

[IDM]

23 hours ago, Clarkey said:

Did you try slewing from the PC to see if the mount was responding from any other software?

Hi, Yes, the telescope mount would respond to Stellarium and accurately found each target I asked it to go to.

On 22/11/2022 at 07:23, 900SL said:

Have you tried swapping cables? I had an issue with ASI Air Pro drift that turned out to be a intermittent cable fault. 

I think changing the cables is a great idea and I did have some spares so they have now been replaced.

Weather wasn't great last night but I quickly put the scope out just to see if the guiding would work. Looking at the graphs it certainly appeared to be working so I hope it might have been primarily caused by the cables.

Thanks,

Ian

[IDM]

19 hours ago, michael8554 said:

The message "RA Calibration Failed: star did not move enough"

Is because you have your guide rates set very low:

RA Guide Speed = 1.5 a-s/s, Dec Guide Speed = 1.5 a-s/s

This is probably because you have the EQMOD "ASCOM PulseGuide setting" on the default value.

Guide speed needs to be at least 7.5 a-s/s.

MultiStar guiding is a way to compensate for "Chasing the Seeing".

So Exposure = 1000 ms is probably okay.

I tried to work out how to make the changes you suggested so opened the Ascom settings. I could see the section on pulse guiding but could not see a slider labelled to change the a-s/s. I will have to work out how to change this. Likewise with the multi-star guiding, I had a look through the PHD2 settings but couldn't see an obvious way to change the setting. I will have to look into this. Any guidance on how to make the changes is gratefully received.

Thanks,

Ian

[IDM]

I just checked my PHD2 guiding settings and it appears to have multi star guiding enabled, so hopefully all good with that

[malc-c]

13 minutes ago, IDM said:

I tried to work out how to make the changes you suggested so opened the Ascom settings. I could see the section on pulse guiding but could not see a slider labelled to change the a-s/s. I will have to work out how to change this. Likewise with the multi-star guiding, I had a look through the PHD2 settings but couldn't see an obvious way to change the setting. I will have to look into this. Any guidance on how to make the changes is gratefully received.

Thanks,

Ian

Ian, these are the two sliders in EQMod that need changing

 

Tick to enable and drag both to the right to give x0.9 rate.  You can leave the other to sliders as default.

Hope that helps

[IDM]

Excellent, thanks Malcolm. I was just ploughing through a YouTube tutorial and you have saved me some time 😀

[alacant]

On 21/11/2022 at 18:25, IDM said:

I found the problem when photographing the Heart Nebula which was nearly vertically above

Hi

You've probably hit the mount limit at the meridian. Set RA to a few minutes after.

Cheers