HEQ5 Tracking Issues

[etunar]

Last week I discovered a reasonably wobble on the RA axis on my HEQ5 which ended up causing lots of double stars on my subs (i am guessing because the mount kept wobbling between the two positions.) So I did the worm gear adjustment and the wobble seems to have disappeared. I did a full slew rotation check and couldn't tell any binding/grinding (I had binding at 1st attempt but was resolved after further adjustments).

Thanks to the clear skies last few nights, I had it running throughout the night 3 times now. My overall guiding is much better than before, averaging between 0.6 and 0.8 Total error. However, when the mount gets closer to the home position (usually after 2-3am), I seem to start having tracking issues. I have attached screenshots to show examples; sometimes it's trailing, sometimes it's double stars, and sometimes it makes a u-turn to track back to the original position.

PHD log files from another night are here: https://openphdguiding.org/logs/dl/PHD2_logs_tych.zip

Is this a balance issue that becomes apparent when the mount is more vertical? I'm relatively new to using this mount, so most of my previous sessions have been closer to the meridian. Or is my worm gear tightened just a bit too much and causing issues? I can't really hear anything wrong when slewing at high speed.

Only other thing i can think of is, I sometimes get error messages on PHD but pulse command being ineffective, but these happen at other times as well without causing any issues.

It's losing me 7-8 frames over the span of 2.5 hours, so it would be nice to get it resolved if anyone has any ideas?

Thanks

[michael8554]

Re The GuideLog for the 17th:

Guiding is generally okay, except for sudden unexplained lurches, up to 30arcsecs in places !

In RA - at 22:04, 02:22, 03:45, 03:53, 03:58

And in Dec at 21:44, 04:28, 04:53

In all cases PHD2 takes a long time to correct, minutes at times

These events are skewing your overall guiding figures.

These lurches could be due to cable snags, or tight spots in your worm-to-wormwheel setting and/or stiction.

But what was you Pulse Guiding Fail message ?

Michael

 

[etunar]

3 hours ago, michael8554 said:

Re The GuideLog for the 17th:

Guiding is generally okay, except for sudden unexplained lurches, up to 30arcsecs in places !

In RA - at 22:04, 02:22, 03:45, 03:53, 03:58

And in Dec at 21:44, 04:28, 04:53

In all cases PHD2 takes a long time to correct, minutes at times

These events are skewing your overall guiding figures.

These lurches could be due to cable snags, or tight spots in your worm-to-wormwheel setting and/or stiction.

But what was you Pulse Guiding Fail message ?

Michael

 

Thanks. Those times line up with the trails in the subs i think.

I checked for cable snags and I can't see anything obvious. How can I check for tight spots in the worm? as i said i couldn't hear anything obvious when slewing at high speed.

The phd message was "PulseGuide command to mount has failed – guiding is likely to be ineffective" - which seems like an occasional loss guide commands?

[michael8554]

6 hours ago, etunar said:

The phd message was "PulseGuide command to mount has failed – guiding is likely to be ineffective" - which seems like an occasional loss guide commands?

There's probably some insight in the DebugLog, which I've never been able to decipher.

But there was no loss of pulse guide during the lurches, all the way through them PHD2 was sending big pulses to try and drag the scope back on track.

Michael

[etunar]

6 hours ago, michael8554 said:

There's probably some insight in the DebugLog, which I've never been able to decipher.

But there was no loss of pulse guide during the lurches, all the way through them PHD2 was sending big pulses to try and drag the scope back on track.

Michael

I guess that's good. PHD was working fine at least. By the way, how do you tell the lurches in the debug log? When I look at it, it all looks random to me.

So do I just re-adjust the worm gear to loosen them up a bit without introducing backlash?

[michael8554]

3 hours ago, etunar said:

By the way, how do you tell the lurches in the debug log?

Like I said, never been able to decipher the DebugLogs.

But in the GuideLog, I deselect RA or Dec so only one is displayed at a time.

Zoom in on the vertical axis to about 3 to 4 arcsecs.

Zoom the horizontal axis to show well separated guidepulses.

Then the Lurches are "off the scale".

Michael

[etunar]

So does anyone have an idea for a solution? 

[michael8554]

On 22/09/2020 at 14:06, michael8554 said:

These lurches could be due to cable snags, or tight spots in your worm-to-wormwheel setting and/or stiction.

 

[etunar]

1 hour ago, michael8554 said:

 

i know you said that - but when i asked how do i check for tight spots, i didn't get a response?

[michael8554]

Probably because you didn't ask how to check for tight spots, you asked for solutions.......

I don't have an EQ mount, but I'd guess you would reduce the worm to wormwheel mesh a tiny amount and try guiding.

Or possibly more likely -  give them a good clean with a toothbrush, then re-grease, metal swarf from the manufacture can get in the teeth and cause those jumps.

I'm surprised no HEQ5 owner has offered any help.

Michael

[etunar]

21 minutes ago, michael8554 said:

Probably because you didn't ask how to check for tight spots, you asked for solutions.......

I don't have an EQ mount, but I'd guess you would reduce the worm to wormwheel mesh a tiny amount and try guiding.

Or possibly more likely -  give them a good clean with a toothbrush, then re-grease, metal swarf from the manufacture can get in the teeth and cause those jumps.

I'm surprised no HEQ5 owner has offered any help.

Michael

you have been more than helpful for someone who doesn't have an EQ mount. I am suprised too - i thought there were lots of people with heq5s..

[kens]

In addition to some pulse guide fails there are also a couple of capture fails on the camera. I can see you had to restart guiding but what else did you do? e.g. did you check the camera connection at those times?

Getting intermittent pulse guide fails and capture fails is suggestive of a USB connection problem. Combined with the intermittent large jumps points to cable snags as a common cause but of course they could be independent issues.

If not cable snags causing the jumps then another possibility is flexure in the guide scope.

[JamesF]

I think it's easier to get past tight spots if you're slewing at high speed, so it might be worth reducing the speed and checking it's still good.

James

[JamesF]

1 minute ago, kens said:

In addition to some pulse guide fails there are also a couple of capture fails on the camera. I can see you had to restart guiding but what else did you do? e.g. did you check the camera connection at those times?

Getting intermittent pulse guide fails and capture fails is suggestive of a USB connection problem. Combined with the intermittent large jumps points to cable snags as a common cause but of course they could be independent issues.

If not cable snags causing the jumps then another possibility is flexure in the guide scope.

Or possibly cables just wobbling as the mount changes position and then settling down again?

James

[etunar]

12 hours ago, kens said:

In addition to some pulse guide fails there are also a couple of capture fails on the camera. I can see you had to restart guiding but what else did you do? e.g. did you check the camera connection at those times?

Getting intermittent pulse guide fails and capture fails is suggestive of a USB connection problem. Combined with the intermittent large jumps points to cable snags as a common cause but of course they could be independent issues.

If not cable snags causing the jumps then another possibility is flexure in the guide scope.

If I remember correct, the restart was due to meridian flip. On my last go, I intentionally woke up around the time on previous nights when i started to have problems (2-3am), and checked for cable snags. I couldn't see anything obvious. USB connection to the mount is via a powered usb 3 hub. Seems ok as I have not had problems with the main camera (using a 1600mm now instead of 6D).

[7170]

How are you guiding the mount - via a camera and ST4 port or direct (EQDIR etc)? If using ST4 try EQDIR or vice versa.

I have seen that effect in the past on my HEQ5 when dithering between images, every now and then one would be ruined, I had to increase the settle time slightly, but I don't believe this is your issue (unless you are dithering?). 

[etunar]

42 minutes ago, 7170 said:

How are you guiding the mount - via a camera and ST4 port or direct (EQDIR etc)? If using ST4 try EQDIR or vice versa.

I have seen that effect in the past on my HEQ5 when dithering between images, every now and then one would be ruined, I had to increase the settle time slightly, but I don't believe this is your issue (unless you are dithering?). 

direct EQDIR at the moment. I am dithering - but not every image - every 5 image if I remember correct.

[7170]

5 minutes ago, etunar said:

direct EQDIR at the moment. I am dithering - but not every image - every 5 image if I remember correct.

I would give it a go without dither in case that is the issue, or add a longer delay after dither. At worst you could eliminate that as a possible issue.

[etunar]

23 hours ago, 7170 said:

I would give it a go without dither in case that is the issue, or add a longer delay after dither. At worst you could eliminate that as a possible issue.

Yea worth a try. I have readjusted the worm gear as well to see if it helps

[7170]

14 minutes ago, etunar said:

Yea worth a try. I have readjusted the worm gear as well to see if it helps

Maybe check if the other gears inside are too loose too. These two videos are worth a watch: Tuning the Backlash on a Skywatcher HEQ5 Pro Mount and HEQ5 Gear Align - Eliminating that grinding noise when you slew. If you do everything in these and then wish to still go further the next options are probably full stripdown and rebuild or Rowan belt mod, so more work.

The suggested star-cross test in PHD2 (per the 1st video) is a good starting point to see how tuned your mount currently is.

[etunar]

On 26/09/2020 at 13:45, 7170 said:

Maybe check if the other gears inside are too loose too. These two videos are worth a watch: Tuning the Backlash on a Skywatcher HEQ5 Pro Mount and HEQ5 Gear Align - Eliminating that grinding noise when you slew. If you do everything in these and then wish to still go further the next options are probably full stripdown and rebuild or Rowan belt mod, so more work.

The suggested star-cross test in PHD2 (per the 1st video) is a good starting point to see how tuned your mount currently is.

Thanks for the links - i did the worm adjustment by following the first video. Not sure how applicable the 2nd video is if you have the belt mod?

I have not done the star test before - probably worth a try. After i did the worm adjustment and used the guide assistant on PHD2, it did report negligible backlash though which was a nice suprise.

[TomBee]

On 24/09/2020 at 23:51, JamesF said:

I think it's easier to get past tight spots if you're slewing at high speed, so it might be worth reducing the speed and checking it's still good.

James

This was true for one of the mounts I've used.

Everything looked ok when checking (with "high" speed) but with the problems always became obvious when using normal tracking speed.

Tommy