Re: Continuation of the discussion using APCC CW up within the East Limit slews with SGPro #APCC


Hi Eric

I use APCC and APPM extensively for unguided exposures on my AP1600

I use SGP exclusively for imaging (I keep saying i'll switch but it's been over a year)

I use just the defaults and enable meridian flip in SGP. it has worked without fail every night

Maybe you have requirements that are unique? I've been following this discussion but i'm at a bit of a loss regarding why it seems to be such a deep and detailed topic when for me it just works. of all the stuff i worry about on a regular basis (accumulation of dust on the telescope for some reason, where is the moon etc.) Meridian flip is the least of my concerns i'd be happy to share my screens and setup with you if you like, just drop me a line


On Sat, May 1, 2021 at 2:25 AM Eric Weiner <weinere@...> wrote:

This is a continuation of a pair of other ap-gto-groups chats regarding using APCC CW up within the East Limits slews with SGPro.

Please, ANYONE with experience with APCC and SGP chime in here.  I didn't intend this to be just between Ray and I.  The question is, which meridian limits settings do you use in SGP when the "CW up in East Limits" is turned on in APCC.  And, which SGP Park Scope and/or Stop Tracking options do you have on/off when APCC horizon and meridian limits are set, turned on, and have "action to take at meridian" set to anything other than "just warn."  The goal is to take advantage of CW up slews in the eastern limits such that no meridian flip is needed for such targets; a hallmark of A-P mounts.

Like I've said in previous posts, I plan to perform a thorough set of supervised experiments with APCC and SGPro using my Mach2 as soon as I can.  I travel for work quite often, so don't have the luxury of being able to get my hands on said pieces of hardware and software as often as I'd like.  I'll post my finding.  Surely other folks have the same questions and concerns.

Instrumentation and automation of scientific and engineering equipment is a daily event for me at work.  I haven't delved into mount control commands, nor have I delved into the inner working of SGP.  Those two aspects of the hobby don't interest me.  A plug and play experience is more enjoyable.  But, I heard about the CW up in the East Limits option in APCC and went down that rabbit hole.  I have seen a number of folks ask similar questions here, over at the SGP forum, and on CN.  I've also read conflicting opinions of its safety when used with SGP or any other automation software.  So it sounds like I'll need to familiarize myself with how the APCC flip point influences SGP in more detail.

I'm numbering these points for ease of reference.  Some folks may have insight on some points and not on others.  In my layman's view, here is why I asked my original question several weeks ago in a different thread:

1a.  We all agree that if you have APCC meridian limits set correctly you are able to start with CW up with scope pointing East, and end CW up with scope pointing West without a risk of a pier collision.  Slews outside the limits will behave in a typical manner w.r.t. CW position and mount side.

2a.  In Ray's video instructions he states the "action when meridian limit reached" must be set to "just warn" for CW up slews in the East limits to work correctly.  So there is no option to have APCC perform a flip in instances where the slew did not land in the limits?  Is this why it must be setup in SGP, so SGP can handle the flip instead of APCC?

3a.   APCC Horizon limits have their own "action when limit reached," so I have set this to "stop tracking" for safety.  If I have the "stop tracking" AND "park" commands turned off (unchecked) in SGP, will APCC simply use the horizon "action when limit reached" command to stop tracking or park when the horizon is reached?  This is just a hypothetical.  I see no reason NOT to use SGP to park the scope once a sequence completes.

4a.  We all agree that in standalone mode (no external software besides APCC) that a slew command within the East Limits (with both limits set IAW Ray's instructions) that the mount will slew with CW up on the west side and scope pointing East.  Then, without any outside influence it will simply track in RA until it reaches the West Horizon Limit, then perform whichever action is set for the horizon limit.

If I'm wrong on any of these points please say so.

Assuming the above is correct, now let's add SGPro into the mix:

1b.  The equipment settings in SGP have the following options with respect to the meridian actions and scope parking / tracking (red arrows):

2b.  The first two red arrows above have to do with actions taken when the SGP sequence completes.  It seems safe to keep this checked and adds an additional safety command in addition to the APCC horizon limit action (assuming it is set to anything other than "just warn").

3b.  The next arrow is the crux of the matter here.  Here are the setting involved with that check box (red arrow):

4b.  So, simply turning these off in SGP and letting APCC handle the limits does not seem like a good option since not all targets in the night's sky will end up with slews within the east limits (and therefore a flip will be necessary).  In other words, slews that DON'T fall within the limits may require a meridian flip to be handled by SGP if imaging starts East of the meridian (other cases exist too).  I'm I off base with this statement?

5b. SGP can handle flip delays past the meridian (red arrow above), but so can APCC (see below).  Which one takes precedence? APCC or SGP?  Do they need to match? Does the "Send limits with offsets to SGPro" make the SGP "Minutes past the meridian to flip" command OBE?  This assumes the box is checked in APCC, I realize it is not in my screenshot below.

6b.  Ray said in a related thread, "All APCC does is send the meridian flip point to SGPro. This value is always displayed in APCC, and I am sure it is working correctly in the latest public APCC builds. I believe the meridian flip point value can be viewed somewhere in SGPro as well, so there should be a way to confirm the value matches what APCC has set."

I understand this, and can definitely see the flip point (or meridian limit) in APCC. I don't know if SGP provides this info. If it does, it's hidden in a log file. Does anyone know if and where to look to see if it matches APCC? What isn't so obvious in my head is how SGP interprets a CW slew when the target falls within the East limits. Any clarification on this would be most appreciated. Else, when I have a chance to play with it myself it will probably become obvious.

7b. Roland said in a previous related thread, "
I would never recommend setting up an automatic remote system with scope starting or ending up in the counterweight up position. Unattended remote operation should always be done with cwt up and flipping sides at the meridian."

No offense intended here, sincerely, but this seems like mixed messages between Ray who (correct me if I'm wrong ) says it's safe to use (conditionally), and Roland who has trepidations.  I'm hoping to hear what Roland's trepidations are.  Sure, glitches can occur with any software, and the standard cwt up and flipping sides at the meridian is a much more vetted operation with little chance of a collision if something fails.  Is that simply the concern?  

Thanks all,


Brian Valente

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