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.

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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.

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