Guiding problem with an L350

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PABr...@aol.com

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Apr 19, 2023, 3:40:55 AM4/19/23
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Guiding works for a few minutes, and then starts oscillating. The mount works OK unguided, but I need guiding.

Brian Valente

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Apr 19, 2023, 11:32:57 AM4/19/23
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Hi Peter

Your calibration is unusable, PHD reported this issue so you will need to sort this out
image.png

ALso the L350 is an encoder mount and needs a different approach to guiding
https://youtu.be/wCu8PKjDZ20 (this is an Astro-Physics video but the settings apply to any absolute encoder mount)

Finally, not sure why the planewave driver does not report guidespeeds? You might ask Planewave about that
RA Guide Speed = Unknown, Dec Guide Speed = Unknown, Cal Dec = 47.3, Last Cal Issue = Orthogonality, Timestamp = 4/17/2023 8:37:30 PM

Brian

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Peter Bresler

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Apr 19, 2023, 11:43:41 AM4/19/23
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Thanks for the advice!  I manually reduced the aggressiveness and hysteresis, which permitted guiding to continue, although stars still were out of round.
 
Peter

 

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Brian Valente

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Apr 19, 2023, 11:48:34 AM4/19/23
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Hi Peter

that may help, but again i recommend watching that video and adjusting your settings for an encoder mount

You will still not get very far until you achieve a good calibration

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Peter Bresler

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Apr 19, 2023, 1:03:52 PM4/19/23
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I may not have included the rotator in the setup


Peter



Brian Valente

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Apr 19, 2023, 1:23:37 PM4/19/23
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>>>I may not have included the rotator in the setup

that would certainly cause issues as you use the rotator, but I don't think that explains the poor calibration results

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Bruce Waddington

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Apr 19, 2023, 1:31:42 PM4/19/23
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I think you should resolve some operational errors before we can really see what’s going on with the mount.  These mounts use a guide speed of 0.5x sidereal, and the lack of reporting from the driver, while unfortunate, doesn’t cause a problem.  As Brian said, you have to get an alert-free calibration or you will just be wasting time.  To start, you should run the new-profile-wizard again to reflect your use of 2x binning.  If you want to switch between different binning levels, create a separate profile for each. Next, you need to spend some time getting a better focus on your guide camera.  The typical star sizes in your guide frames are over 8px which is too large for your guider image scale and results in too many lost-star events and too few usable stars for multi-star guiding.  To get a critical focus, you need to use a mechanism that will provide quantitative feedback on star size – the PHD2 Star Profile tool can do that or you can use another app like SharpCap.  Your last calibration was degraded because of lost-star events (because of poor focus) and the wrong calibration step-size.  Fix those things, then concentrate on getting a good calibration.  Do the calibration near Dec=0 and within about 15 degrees of the celestial meridian.  Once you have re-run the new-profile-wizard, don’t start fiddling around with the guider settings – your problems are not with PHD2, they are coming from operating errors and probably the mount.  The unguided session you ran at 20:51 suggests there’s something wrong with the native mount behavior but until we can get a better calibration, it’s hard to be sure.  As you know, balance on these systems is very important and they are sensitive to wind as well. If you can get a cleaner set of data with all these other things sorted out, we can probably help you more.  With lost-star events eliminated and a more accurate calibration, a long Guiding Assistant session will reveal a lot about what’s going on with the mount.

 

Good luck,

Bruce

Bruce Waddington

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Apr 19, 2023, 1:53:07 PM4/19/23
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Also, you should upgrade to the latest dev release, 2.6.11dev4.

Bruce

Peter Bresler

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Apr 19, 2023, 2:52:50 PM4/19/23
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Thanks. I did run the new profile wizard, but will try again tonight, conditions permitting. The mount is well balanced. I just ran another thorough autotune on it.
 
Peter

Peter Bresler

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Apr 19, 2023, 3:11:03 PM4/19/23
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Thanks for the advice. I will try again tonight conditions permitting.
 
Peter

Peter Bresler

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Apr 20, 2023, 4:06:53 AM4/20/23
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I ran another calibration using advice for Astro-physics encoder mounts. Calibration completed. Guiding looks good, although stars still sometimes are slightly out of round. How does it look to you?
 
 
Peter
 

In a message dated 4/19/2023 8:32:59 AM Pacific Standard Time, bval...@gmail.com writes:
 

 

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Brian Valente

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Apr 20, 2023, 11:12:35 AM4/20/23
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Hi Peter

These don't look like the values outlined in the video. This looks like you are running an earlier version of 2.6.11? You need at least 2.6.11 dev 1 to use the encoder features. Dev 4 is the latest, I highly recommend you update to that. You aren't getting all the features mentioned in the video

your calibration is better, but there is still something going on with your mount. I think you need to show your logs to Planewave. L series mounts can be finicky when it comes to tuning them. 

The axes should show a series of equally spaced points on the line, look at your last calibration:

image.png



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Peter Bresler

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Apr 20, 2023, 1:18:41 PM4/20/23
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It is 2.6.11. I agree with you about the mount; I attempted another autotune with no improvement, and sent a message to Planewave.
 
Peter
Phd2 version.jpg

Brian Valente

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Apr 20, 2023, 1:38:34 PM4/20/23
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Peter to use the encoder settings you need the latest dev release. The features shown in the video aren't available in 2.6.11 so no wonder why some of this didn't work


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Peter Bresler

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Apr 20, 2023, 1:44:02 PM4/20/23
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I went to the Phd2 website and downloaded the latest available version. I agree about not being able to find features in the video, but the parameters were entered in the correct categories. At this point the mount is not tracking at less than 2 RMS in RA, which it should do. PW has done tuning on it previously with their own utility. AP is a lot better, I would trade it for a Mach2!

Brian Valente

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Apr 20, 2023, 1:51:39 PM4/20/23
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Peter you are on the latest *release* version, not the latest Dev version

Please see the link prior

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Bruce Waddington

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Apr 20, 2023, 1:57:44 PM4/20/23
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In addition to upgrading to the latest dev release and following all the other instructions for getting a reasonable calibration, I suggested before that you do an extended run with the Guiding Assistant.  That will collect quantitative data that shows how the mount performs on its own and it will make it much easier for PW to understand what’s going on.  It sounds like you aren’t running the dev release.  Disable the checkbox for ‘Only major releases’ on the Global tab of Advanced Settings.  Or download the latest dev release from here:  https://openphdguiding.org/development-snapshots/

 

Bruce

image001.png
image002.png

Peter Bresler

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Apr 20, 2023, 2:00:15 PM4/20/23
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I just downloaded and installed the dev release, but autotune did not produce a satisfactory result for unguided tracking.
 
Peter
L350 tracking.jpg

Brian Valente

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Apr 20, 2023, 2:06:07 PM4/20/23
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Hi Peter

I really encourage you to go back and watch that video. It discusses why you may want guiding for encoder mounts in general. Even with absolute encoders and a sky model on my AP1600 I still use guiding. 

I think you have two separate issues:

As Bruce is mentioning, the basic performance of the mount seems like an issue. Capturing a guiding assistant run (i.e., unguided results) and sharing those with planewave will help them the most

Separately, for guiding you should follow the recommendations in the video. You could not have set those properly without a dev release, so now that you have a release that supports the features for encoder mounts, you should be good here. As previously mentioned, I don't think this is your main issue right now  

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Peter Bresler

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Apr 20, 2023, 2:15:26 PM4/20/23
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I also have a 1600 and have had no problems with it except for an episode when a deposit formed on the DEC encoder strip. I may be moving my CDK 12.5 over to it.
 
Peter

oliv...@gmail.com

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Apr 20, 2023, 4:26:05 PM4/20/23
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Hi

We are using an L500 with a CDK17 in Chile (remote) since 1 year and half.

We guide it using a QHY178mm (bin 1 or 2) and an OAG and PHD2. 
Basically we use a 5s exposure time and increased Histeresis value. RA  Agr. about 0.7 and DEC agr. about 0,3 to 0,5.

We used all PHD2 dev versions since December 2021 without any problem.

Concerning the L500 : direct drive mount are very sensitive to balance and wind, though the PW mounts are less sensitive than other.
At the beginning the DEC drive was not stiff enough with default values and we had to request an remote investigation from PW which they did from California. (None of us were in Chile nor close to the mount. I am in Europe). So after in situ tests with state of the art Software, PW increased the DEC motor torque a bit (there is still plenty of margin if needed).
Once the mount has been fine tuned we got:
- sub 0,1 rms at the encoders without wind.
- with light wind i.e. 1 hour after sunset and 1h before sunrise, both axis oscillate more or less : about 1 ´‘ peak for RA and 1,5’´ for DEC.

(Which is different from PHD2)

The mount needs :
- a proper polar alignment (use both PW software and PHD2 drift alignment utility)
- a (about) 75 points pointing model (we tried up to 200 with no significant improvement)
- auto tune (use advanced tuning, much longer but may help a l
bit)

Once these basics are validated, you can start using PHD2.

- Calibrate only once close to the meridian (between +1 and +5deg after for instance) and on the equator. (Use the PHD2 pointing feature of the drift alignment function to point to this area and cancel the alignment).
- force the « DEC orthogonal to RA » option
- calibrate without wind and after a sufficient cool down time. At least 1h with the CDK12,5 having its fans running.
- you should (must) get a good calibration with about 10 points (8-12) on both axis with marginal orthogonality error.
-3s exposure is fine while calibrating. (And 5s while guiding)
A proper calibration is mandatory. Without a very good calibration there is no hope in getting good guiding.

Now in PHD2 you should get sub 0,35’´ without wind for RA and a little bit less for DEC. (best case RA sub 0,2’´ and DEC sub 0,1’´)

This is greatly linked to the seeing: 
a poor seeing without wind will give you a poor guiding at PDH2 though a perfect guiding at the encoders.

Clear skies

Olivier 

Le 20 avr. 2023 à 20:15, 'Peter Bresler' via Open PHD Guiding <open-phd...@googlegroups.com> a écrit :



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On Thu, Apr 20, 2023 at 1:06 AM 'Peter Bresler' via Open PHD Guiding <open-phd...@googlegroups.com> wrote:

I ran another calibration using advice for Astro-physics encoder mounts. Calibration completed. Guiding looks good, although stars still sometimes are slightly out of round. How does it look to you?

 

 

Peter

 


In a message dated 4/19/2023 8:32:59 AM Pacific Standard Time, bval...@gmail.com writes:

 

Hi Peter

 

Your calibration is unusable, PHD reported this issue so you will need to sort this out

<image002.png>

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/735462776.6693042.1682014519323%40mail.yahoo.com.
<image001.png>
<image002.png>

Peter Bresler

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Apr 20, 2023, 4:36:07 PM4/20/23
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Thanks! That is useful information. I think wind is a problem here also for the mount.

Peter Bresler

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Apr 20, 2023, 10:15:52 PM4/20/23
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I ran another thorough autotune on the mount, and the unguided tracking looks as it should. I will run another pointing model tonight.
 
Peter
L350 trackinking-OK.jpg
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