Excessive Slew Warnings in APPM


Brent Boshart
 
Edited

I have been trying to troubleshoot excessive slew warnings (over 50%) when building models in APPM. From observing the Dec coordinate values in APPC I believe it is the Dec axis.  Here is what I have done:
 
I have meticulously balanced the Dec axis. During a live view, I rapped my pier and the mount with my hand and the view settles within 2 seconds or less.
 
I ran a test with the "Settle Time" as high as 60 seconds and had the same frequency of slew errors compared to an 8 second settle time.
 
I earlier had worked with A-P to increase encoder dampening trying variations from my original to the maximum suggested. Btw, this is not with a very heavy payload - a Stowaway with ASI2600MM/filter wheel/OAG.
 
I have examined the model building images and the stars appear round.
 
When I watch the Dec coordinate readout in APPC during the settle time, I can pretty much tell when I will get a slew warning by the amount of fluctuation of the reading. I guessing 0.5 arcseconds is the cut-off point to issue a warning? Sometimes my reading can fluctuate as much as 0.8 arcseconds but usually around 0.5-0.6 when I get the warning. The RA axis readings seem much more stable (even when multiplied by 15 to get the same units).
 
So my question is does this matter or am I chasing something inconsequential - do I uncheck "Require high accuracy slews" and be on my way? Or what would I try next? Is there perhaps a mechanical tweak I need to try with the Dec axis?   

(Edit - forgot to mention this is the Mach2GTO)


 

Hi Brent

I have experienced that as well. My decision was to leave the high accuracy slews enabled and live with those warnings.

Prior to having the high accuracy option available, my main concern was streaking stars for model building . I have run a number of 300 point models and kept all the frames to review. I would often see a handful or more of plates with streaking stars

Sometimes these streaking stars would cause plate solve to fail, but other times the solve would work even if the stars weren't pinpoint. I was worried this could create inaccuracies in the model. Since I enabled high accuracy, I only get pinpoint stars in the model building and no failed solves. I have set my settle time around 10 seconds (it's a big 20" CDK). 

hth

Brian




On Mon, May 9, 2022 at 6:44 AM Brent Boshart <bboshart@...> wrote:
I have been trying to troubleshoot excessive slew warnings (over 50%) when building models in APPM. From observing the Dec coordinate values in APPC I believe it is the Dec axis.  Here is what I have done:
 
I have meticulously balanced the Dec axis. During a live view, I rapped my pier and the mount with my hand and the view settles within 2 seconds or less.
 
I ran a test with the "Settle Time" as high as 60 seconds and had the same frequency of slew errors compared to an 8 second settle time.
 
I earlier had worked with A-P to increase encoder dampening trying variations from my original to the maximum suggested. Btw, this is not with a very heavy payload - a Stowaway with ASI2600MM/filter wheel/OAG.
 
I have examined the model building images and the stars appear round.
 
When I watch the Dec coordinate readout in APPC during the settle time, I can pretty much tell when I will get a slew warning by the amount of fluctuation of the reading. I guessing 0.5 arcseconds is the cut-off point to issue a warning? Sometimes my reading can fluctuate as much as 0.8 arcseconds but usually around 0.5-0.6 when I get the warning. The RA axis readings seem much more stable (even when multiplied by 15 to get the same units).
 
So my question is does this matter or am I chasing something inconsequential - do I uncheck "Require high accuracy slews" and be on my way? Or what would I try next? Is there perhaps a mechanical tweak I need to try with the Dec axis?   




Dean Jacobsen
 
Edited

Where does the "slew settle time" parameter come into play here?  [APPM Measurement Points tab --> Slew Settle Time]  I don't have the "require high accuracy slews" feature enabled and I have the slew settle time set to 2 seconds.  I haven't seen any streaking stars in the plate solve photos... but i haven't been looking for it either.  I am going to start watching the plate solve images.

Edit:  OK, for some reason I didn't see Brian's mention that he uses 10 second settle time with the large scope.
  --
Dean Jacobsen
Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/


 

>>> Edit:  OK, for some reason I didn't see Brian's mention that he uses 10 second settle time with the large scope.

that's correct - it's a big truss. While we were trying to diagnose some issues, I experimented with the settle time here and found this was the best for my situation

Brian

On Mon, May 9, 2022 at 8:55 AM Dean Jacobsen <deanjacobsen@...> wrote:

[Edited Message Follows]

Where does the "slew settle time" parameter come into play here?  [APPM Measurement Points tab --> Slew Settle Time]  I don't have the "require high accuracy slews" feature enabled and I have the slew settle time set to 2 seconds.  I haven't seen any streaking stars in the plate solve photos... but i haven't been looking for it either.  I am going to start watching the plate solve images.

Edit:  OK, for some reason I didn't see Brian's mention that he uses 10 second settle time with the large scope.
  --
Dean Jacobsen
Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/




Roland Christen
 

What mount is this?

Roland

-----Original Message-----
From: Brent Boshart <bboshart@...>
To: main@ap-gto.groups.io
Sent: Mon, May 9, 2022 8:44 am
Subject: [ap-gto] Excessive Slew Warnings in APPM

I have been trying to troubleshoot excessive slew warnings (over 50%) when building models in APPM. From observing the Dec coordinate values in APPC I believe it is the Dec axis.  Here is what I have done:
 
I have meticulously balanced the Dec axis. During a live view, I rapped my pier and the mount with my hand and the view settles within 2 seconds or less.
 
I ran a test with the "Settle Time" as high as 60 seconds and had the same frequency of slew errors compared to an 8 second settle time.
 
I earlier had worked with A-P to increase encoder dampening trying variations from my original to the maximum suggested. Btw, this is not with a very heavy payload - a Stowaway with ASI2600MM/filter wheel/OAG.
 
I have examined the model building images and the stars appear round.
 
When I watch the Dec coordinate readout in APPC during the settle time, I can pretty much tell when I will get a slew warning by the amount of fluctuation of the reading. I guessing 0.5 arcseconds is the cut-off point to issue a warning? Sometimes my reading can fluctuate as much as 0.8 arcseconds but usually around 0.5-0.6 when I get the warning. The RA axis readings seem much more stable (even when multiplied by 15 to get the same units).
 
So my question is does this matter or am I chasing something inconsequential - do I uncheck "Require high accuracy slews" and be on my way? Or what would I try next? Is there perhaps a mechanical tweak I need to try with the Dec axis?   

--
Roland Christen
Astro-Physics


Brent Boshart
 

Mach2GTO


Roland Christen
 

We'll get on it and let you know shortly.

Roland



-----Original Message-----
From: Brent Boshart <bboshart@...>
To: main@ap-gto.groups.io
Sent: Mon, May 9, 2022 11:52 am
Subject: Re: [ap-gto] Excessive Slew Warnings in APPM

Mach2GTO

--
Roland Christen
Astro-Physics


Mike Hanson
 

Hi Brent,

Please uncheck the "Require High Accuracy slews".  The threshold is too small for the small aperture of the DEC axis encoder.

Regards,
Mike Hanson


Howard Hedlund
 

Hi Brent,

I should point out that this does NOT hurt anything or imply anything bad.  In fact, as I understand things, it indicates that the encoders are working as they should.

Clear, Mag. 7 Skies

Howard


Howard Hedlund
 

I should have added that I am in complete agreement with Mike Hanson's recommendation.

HKH


Brent Boshart
 
Edited

Thanks for all the replies - great support. I did not think anything was drastically wrong as I have good pointing and excellent guiding with my mount. It would seem logical to have "Require High Accuracy Slews" checked especially when modelling for "Dec Arc Tracking" and frequent "Slew Warning" messages seems like something is not optimum. Perhaps a future version of APPM could adjust the threshold according to the mount/encoders being modelled.  "Slew warning" messages would be helpful if something is not optimum.


Roland Christen
 

We are working on a solution, but like all software changes it will require some extensive testing to get it right. The mount is not the issue, it's the way that the APPM slew warning software works that will need some changes. The mount itself gets there bang on, regardless whether low or high res warning is set. The mount always gets to the same exact point regardless of where the warning is set, or if no warning is set.

Roland

-----Original Message-----
From: Brent Boshart <bboshart@...>
To: main@ap-gto.groups.io
Sent: Tue, May 10, 2022 11:17 am
Subject: Re: [ap-gto] Excessive Slew Warnings in APPM

Thanks for all the replies - great support. I did not think anything was drastically wrong as I have good pointing and excellent guiding with my mount. It would seem logical to have "Require High Accuracy Slews" checked especially when modelling for "Dec Arc Tracking" and frequent "Slew Warning" messages seems like something is not optimum. Perhaps a future version of APCC could adjust the threshold according to the mount/encoders being modelled.  "Slew warning" messages would be helpful if something is not optimum.  

--
Roland Christen
Astro-Physics


Roland Christen
 

Another way to understand what is happening is this: the mount pointing position remains exactly the same regardless of the setting of the low accuracy or high accuracy setting. "Require High Accuracy Slews" is really a misnomer, in that this setting has no bearing at all on where the mount itself points, or the position that it ends up in. It is not part of the control loop. The actual position control loop is inside the mount's servo system and is not accessible to outside software. This internal control loop is always set to the highest inherent accuracy of the encoders, and is not controllable by external means.

Rolando

-----Original Message-----
From: Roland Christen via groups.io <chris1011@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Tue, May 10, 2022 11:32 am
Subject: Re: [ap-gto] Excessive Slew Warnings in APPM

We are working on a solution, but like all software changes it will require some extensive testing to get it right. The mount is not the issue, it's the way that the APPM slew warning software works that will need some changes. The mount itself gets there bang on, regardless whether low or high res warning is set. The mount always gets to the same exact point regardless of where the warning is set, or if no warning is set.

Roland

-----Original Message-----
From: Brent Boshart <bboshart@...>
To: main@ap-gto.groups.io
Sent: Tue, May 10, 2022 11:17 am
Subject: Re: [ap-gto] Excessive Slew Warnings in APPM

Thanks for all the replies - great support. I did not think anything was drastically wrong as I have good pointing and excellent guiding with my mount. It would seem logical to have "Require High Accuracy Slews" checked especially when modelling for "Dec Arc Tracking" and frequent "Slew Warning" messages seems like something is not optimum. Perhaps a future version of APCC could adjust the threshold according to the mount/encoders being modelled.  "Slew warning" messages would be helpful if something is not optimum.  

--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Brent Boshart
 

Since this original post, I have kept "Require high accuracy slews" unchecked using my MACH2GTO.  I noticed the firmware update "VCPx-P02-13" mentions "Improve stability of reported coordinates in an encoder mount".  Is this to address the slew warnings in APPM?  I installed VCPx-P02-13 today and tried APPM tonight with "Require high accuracy slews" checked - I still experienced a lot of slew warnings.  So I will still keep it unchecked but was just curious if the firmware update was to address that? 


Mike Hanson
 

Hi Brent,

The firmware change you refer to addresses a couple of items, including reducing two of the contributors to the slew warning.  However, the primarily beneficiary is the DEC axis.  If you provide APCC logs files, we'll be able to determine which axis is producing the warning, and by how much.


Regards,
Mike Hanson