APCC Meridian Tracking Limits and Sequence Generator Pro


psparkman@...
 

I have posted a couple of times about Meridian Flip issues with APCC v1.9.0.11 and Sequence Generator Pro.  This worked reliably for several months with the previous version, but I now think that was related to my settings at that time.  I took advantage of a cloudy night to learn more about how the Meridian tracking limits in APCC work and relate to SGP.  I now think that I understand how it works, but am not sure why it works the way it does in relation to the "Counterweight Up Slews within:" check boxes for East and West and how they interact with the "Send Limit with offset to SGPro" checkbox.

I now clearly understand why I was having Meridian flip failures with the settings set in a way to take advantage of the variable Meridian limits versus Dec position.  First, it must be understood that SGP issues a Meridian Flip by sending a slew command to same target coordinates that it is currently tracking.  Thus relying on the mount to do the flip and come back to the same coordinates.  This is the issue with my flip failures.  When I set the CW up slews within check box for West and set the  send limit to SGP box with a flip offset of my longest exposure plus five minutes to keep from tracking into the meridian limit before a flip; SGP sends a slew command to the same location it is currently tracking and the mount does a safety slew back to the meridian, then comes right back counterweight up because of the CW up slew within West limit check box.  This causes SGP to see that the scope is still on the west side of the pier and it aborts, parks, and shuts down.

So all of that makes sense, but the CW up slews within West check box clearly does not cooperate with SGP.  So why did I check that in the first place?

This is where I don't understand why a couple of things function the way they do with APCC.  I really never want to do CW up slews within West limits for imaging.  It might save a flip if you are going between close objects, but I would rather it go ahead and put the scope on the east and it will not work with the slew in place meridian flip design of SGP.  The problem is that if I check the "Send limit to with offset to SGPro" check box WITHOUT the CW Up slews within West limits box checked, APCC just sends a 0.0 offset to SGP and I don't get to take advantage of the tracking limits being set automatically to match the limits that I have set for my scope and mount.

pastedGraphic.png

The only way to get the Dec specific offset to pass to SGP is to check the West Limits box, but that will not work for SGP Meridian flips.
 
Why doesn't this just pass the current limit offset to SGP without having to check the West Limits check box?  So checking the Send Limit with offset to SGPro check box doesn't seem to do anything unless the West Limits box is checked.

Here is how it looks with the box checked showing the correct offset, but the West box needing to be checked.

pastedGraphic_1.png

So, next I thought that I would try checking the East limits box.  At least that makes some sense from an imaging perspective as it could allow the imaging to start with the CW up and the scope on the East side and avoid the flip all together.  But the problem is that if you check that box, it forces the West Limits box to be checked for some reason.  So that option will not work.  I noticed another little issue when I tried the CW Up slews East box checked with SGP.  When SGP slews then centers on a target, I don't get within the 20 pixel limit with the first plate solve.  Usually with a 60 point APPM model I get within 100-200 pixels, so SGP sends a new calibrated slew command to get it within 20 pixels.  This invokes the safety slew, so the mounts has to take the time to go back to the meridian, then move back.  Sometimes this can take 2 or more tries and the safety slew does take more time. 

What I expect should happen is that I can check either East or West Limits without the East forcing the West.  Also, I should be able check the Send Limits to SGPro box and have the offsets pass correctly without having either CW Up limit box checked.  That would then work fine with the SGP Meridian flip function, and allow the mount to track CW up to the limits APCC sets and take advantage of that capability.

With the way that it currently works, I am just unchecking the CW slew limits and Send Limits to SGPro boxes and setting a fixed 1 hour offset in SGP since that is my smallest time past Meridian limit.  But I would much rather these functions work as expected.


Ray Gralak
 

So all of that makes sense, but the CW up slews within West check box clearly does not cooperate with SGP.
So why did I check that in the first place?
"CW up slews" invokes APCC to change the meridian delay. With it off, the appropriate action will be taken when the limit is reached, but any slew to the West side from a counterweight-up position will cause a pier flip.

So, "CW up slews in West" MUST be selected or any slew that SGPro issues after the meridian will cause a pier flip.

-Ray


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of psparkman via groups.io
Sent: Sunday, October 31, 2021 8:23 PM
To: main@ap-gto.groups.io
Subject: [ap-gto] APCC Meridian Tracking Limits and Sequence Generator Pro

I have posted a couple of times about Meridian Flip issues with APCC v1.9.0.11 and Sequence Generator Pro.
This worked reliably for several months with the previous version, but I now think that was related to my
settings at that time. I took advantage of a cloudy night to learn more about how the Meridian tracking limits
in APCC work and relate to SGP. I now think that I understand how it works, but am not sure why it works the
way it does in relation to the "Counterweight Up Slews within:" check boxes for East and West and how they
interact with the "Send Limit with offset to SGPro" checkbox.

I now clearly understand why I was having Meridian flip failures with the settings set in a way to take
advantage of the variable Meridian limits versus Dec position. First, it must be understood that SGP issues a
Meridian Flip by sending a slew command to same target coordinates that it is currently tracking. Thus relying
on the mount to do the flip and come back to the same coordinates. This is the issue with my flip failures.
When I set the CW up slews within check box for West and set the send limit to SGP box with a flip offset of
my longest exposure plus five minutes to keep from tracking into the meridian limit before a flip; SGP sends
a slew command to the same location it is currently tracking and the mount does a safety slew back to the
meridian, then comes right back counterweight up because of the CW up slew within West limit check box.
This causes SGP to see that the scope is still on the west side of the pier and it aborts, parks, and shuts
down.

So all of that makes sense, but the CW up slews within West check box clearly does not cooperate with SGP.
So why did I check that in the first place?

This is where I don't understand why a couple of things function the way they do with APCC. I really never
want to do CW up slews within West limits for imaging. It might save a flip if you are going between close
objects, but I would rather it go ahead and put the scope on the east and it will not work with the slew in place
meridian flip design of SGP. The problem is that if I check the "Send limit to with offset to SGPro" check box
WITHOUT the CW Up slews within West limits box checked, APCC just sends a 0.0 offset to SGP and I don't
get to take advantage of the tracking limits being set automatically to match the limits that I have set for my
scope and mount.

pastedGraphic.png<blob:https://ap-gto.groups.io/8b047c01-5345-4a4a-9826-0dfc32cfc854>

The only way to get the Dec specific offset to pass to SGP is to check the West Limits box, but that will not
work for SGP Meridian flips.

Why doesn't this just pass the current limit offset to SGP without having to check the West Limits check box?
So checking the Send Limit with offset to SGPro check box doesn't seem to do anything unless the West
Limits box is checked.

Here is how it looks with the box checked showing the correct offset, but the West box needing to be
checked.

pastedGraphic_1.png<blob:https://ap-gto.groups.io/3613deea-33e3-4609-82d2-190b37dc6e83>

So, next I thought that I would try checking the East limits box. At least that makes some sense from an
imaging perspective as it could allow the imaging to start with the CW up and the scope on the East side and
avoid the flip all together. But the problem is that if you check that box, it forces the West Limits box to be
checked for some reason. So that option will not work. I noticed another little issue when I tried the CW Up
slews East box checked with SGP. When SGP slews then centers on a target, I don't get within the 20 pixel
limit with the first plate solve. Usually with a 60 point APPM model I get within 100-200 pixels, so SGP sends
a new calibrated slew command to get it within 20 pixels. This invokes the safety slew, so the mounts has to
take the time to go back to the meridian, then move back. Sometimes this can take 2 or more tries and the
safety slew does take more time.

What I expect should happen is that I can check either East or West Limits without the East forcing the West.
Also, I should be able check the Send Limits to SGPro box and have the offsets pass correctly without
having either CW Up limit box checked. That would then work fine with the SGP Meridian flip function, and
allow the mount to track CW up to the limits APCC sets and take advantage of that capability.

With the way that it currently works, I am just unchecking the CW slew limits and Send Limits to SGPro boxes
and setting a fixed 1 hour offset in SGP since that is my smallest time past Meridian limit. But I would much
rather these functions work as expected.




psparkman@...
 

Ray, I am not sure why I can't communicate the issue to you properly, but I will continue to try.  I don't want to check the CW up slew west box.  I do want any slew command issued by SGP past the meridian to cause a meridian flip as that is how SGP initiates a flip.  However, I do want the mount to track past the meridian to the APCC limit minus the offset and pass that value to SGP so that it will invoke the flip at the delayed point and take advantage of the ability to track past the meridian.

The problem that I have is that without having the CW up slews within West limits box checked, APCC does not pass the additional meridian delay as shown in my first screenshot above.  I feel that this is a bug.  Also, why does checking the CW Up slew limits for the East automatically check the one for the West? 


Ray Gralak
 

That's not going to work because you can't guarantee that SGPro won't issue a slew after the meridian.

Without APCC actually setting the meridian delay SGPro would not expect the mount to flip if it had to recenter the image, or slew to another target that normally would not require a pier flip because it is within the West limit.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of psparkman via groups.io
Sent: Sunday, October 31, 2021 8:50 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APCC Meridian Tracking Limits and Sequence Generator Pro

Ray, I am not sure why I can't communicate the issue to you properly, but I will continue to try. I don't want to
check the CW up slew west box. I do want any slew command issued by SGP past the meridian to cause a
meridian flip as that is how SGP initiates a flip. However, I do want the mount to track past the meridian to the
APCC limit minus the offset and pass that value to SGP so that it will invoke the flip at the delayed point and
take advantage of the ability to track past the meridian.

The problem that I have is that without having the CW up slews within West limits box checked, APCC does
not pass the additional meridian delay as shown in my first screenshot above. I feel that this is a bug. Also,
why does checking the CW Up slew limits for the East automatically check the one for the West?


psparkman@...
 

It might be more efficient if we could talk.  Would you be willing to send your phone number and time to talk to my email address listed?


Ray Gralak
 

Honestly, I'm pretty busy working on software now. But I don't think there is anything to discuss. APCC sends the mount's flip point to SGPro, which is exactly what SGPro expects. Changing the meaning of that would invalidate the purpose of that SGPro API, so I do not think it is the right thing to do.

BTW, A-P will soon start a new website where people can suggest features and others can vote on them. When it's available, you can describe your feature request there and have others vote for it.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of psparkman via groups.io
Sent: Sunday, October 31, 2021 9:21 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APCC Meridian Tracking Limits and Sequence Generator Pro

It might be more efficient if we could talk. Would you be willing to send your phone number and time to talk
to my email address listed?


psparkman@...
 

Ok, thanks Ray.


steve.winston@...
 

Hi Ray,

>That's not going to work because you can't guarantee that SGPro won't issue a slew after the meridian.

That's fine as this is exactly the expected and documented behavior for SGP:  If the mount is at or past SGP's configured meridian limit, then issuing a slew command should result in a meridian flip.  

In the current implementation of APCC it appears that APCC is basically intercepting the slew command when "CW up slews within West limits" box is checked, preventing the meridian flip from completing, and causing SGP to abort.

Is there a way to configure APCC to ensure that when SGP reaches it's configured meridian limit and issues the slew command, the meridian flip can complete?

thanks!

Steve



Ray Gralak
 

Hi Steve,

In the current implementation of APCC it appears that APCC is basically intercepting the slew command when
"CW up slews within West limits" box is checked, preventing the meridian flip from completing, and causing
SGP to abort.
It doesn't work that way. The mount's flip point is controlled by the meridian delay set in the mount. The cause of the flip failure is probably a time discrepancy between the mount's meridian delay value and when SGPro thinks it is okay to flip. If there is even a split-second difference between the two times, that could prevent the pier flip from occurring if SGPro sends the slew command at the exact moment a flip should work. If SGPro delayed a few seconds, it might solve the problem. The new flip padding control in the 1.9.1.3 beta tries to address this timing issue.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of steve.winston@gmail.com
Sent: Monday, November 1, 2021 9:15 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APCC Meridian Tracking Limits and Sequence Generator Pro

Hi Ray,

That's not going to work because you can't guarantee that SGPro won't issue a slew after the meridian.
That's fine as this is exactly the expected and documented behavior for SGP: If the mount is at or past
SGP's configured meridian limit, then issuing a slew command should result in a meridian flip.

In the current implementation of APCC it appears that APCC is basically intercepting the slew command when
"CW up slews within West limits" box is checked, preventing the meridian flip from completing, and causing
SGP to abort.

Is there a way to configure APCC to ensure that when SGP reaches it's configured meridian limit and issues
the slew command, the meridian flip can complete?

thanks!

Steve