SGP Pier flip failure (AP1100/APMM pro and SGP)

Recently I’ve had SGP fail to execute a pier flip and lost two evenings of precious clear skies. I thought I had everything set up correctly, as many nights have worked out great. But alas, maybe not.

I have an AP1100GTO mount operating under APCC Pro and SGP

I have setup APCC to use meridian limits so that I can have CWUP within the safe zones with Pier side east so that in those cases a pier flip is not necessary. However, when that is not possible (high DECs) the OTA must pier flip.

Here is the section of the log that shows the issue (I can send the entire file if needed, but I’m not on a cumputer where I can do that right now):

[11/10/20 00:04:49.099][DEBUG][Sequence Thread][SQ;] Sending commands…
[11/10/20 00:04:49.099][DEBUG][Sequence Thread][SQ;] SetFlatBox: Frame Type is Light
[11/10/20 00:04:49.099][DEBUG][Sequence Thread][SQ;] EventMarker(2) - t:NGC 1514 (0); e:3; f:1; o:
[11/10/20 00:04:49.099][DEBUG][Sequence Thread][SQ;] Checking if Meridian Flip is needed
[11/10/20 00:04:49.101][DEBUG][Sequence Thread][SQ;] Telescope is on the West side of the mount
[11/10/20 00:04:49.105][DEBUG][Sequence Thread][SQ;] Meridian Flip needed, Hour Angle >= Degrees Past To Flip: -13.4899333333333 >= -14.75
[11/10/20 00:04:49.105][DEBUG][Sequence Thread][SQ;] Running blocking meridian flip…
[11/10/20 00:04:49.105][DEBUG][Main Thread][SQ;] Adding sequence level notification: Running automatic pier flip…
[11/10/20 00:04:49.119][DEBUG][Sequence Thread][SQ;] Sending Notification: Status - Running automatic pier flip…
[11/10/20 00:04:49.128][DEBUG][Main Thread][SQ;] Adding sequence level notification: Cannot Run Meridian Flip:
-Telescope must be pointed across the meridian to pier flip.

[11/10/20 00:04:49.186][DEBUG][Main Thread][SQ;] Sending Notification: Error - Cannot Run Meridian Flip:
-Telescope must be pointed across the meridian to pier flip.

[11/10/20 00:04:49.191][DEBUG][Main Thread][SQ;] Adding sequence level notification: Failed to complete automatic meridian flip, aborting sequence!
[11/10/20 00:04:49.261][DEBUG][Sequence Thread][SQ;] Sending Notification: Error - Failed to complete automatic meridian flip, aborting sequence!
[11/10/20 00:04:54.352][DEBUG][Image History Worker][SQ;] Star detection using min star size of 2px…
[11/10/20 00:04:54.353][DEBUG][Image History Worker][SQ;] Star detection using max star size of 40px…
[11/10/20 00:04:54.471][DEBUG][Image History Worker][SQ;] Find stars took: 6032 ms…
[11/10/20 00:04:54.471][DEBUG][Image History Worker][SQ;] Star list contains 31 stars…
[11/10/20 00:04:54.471][DEBUG][Image History Worker][SQ;] Calculating HFR with sample size: 2
[11/10/20 00:04:54.821][DEBUG][Image History Worker][SQ;] Image analysis (async) END
[11/10/20 00:05:30.303][DEBUG][Main Thread][SQ;] PopulateDataModel: Transferring view to the data model…
[11/10/20 00:05:30.318][DEBUG][MF Update Thread][SQ;] Performing serialize…
[11/10/20 00:05:51.104][DEBUG][Sequence Thread][SQ;] Blocking Pier Flip: Failed to meridian flip, aborting sequence (True)
[11/10/20 00:05:51.104][DEBUG][Sequence Thread][SQ;] Aborting sequence: Failed to meridian flip
[11/10/20 00:05:51.104][DEBUG][Sequence Thread][SQ;] Set sequence abort

Your mount thinks it has not crossed the meridian and is refusing. Could be caused by an invalid lat / lon, but I can’t be sure. Worst case, you could also turn on logging for your mount and see where it thinks it is at the point of request.

Check that your East and West limits in APCC are not inverted (click Show East limit checkbox and make sure that the limits toggling on and off are on the East side of the sky, same for West). It’s not too difficult to invert them when you create the limits (ask me how I know …) and it triggers a pier flip when the mount is still West pointing East, which causes a failure in SGP. Also, if you haven’t updated APCC to the latest version you may want to do so. Ray Gralak made some bux fixes a couple of minor revs ago that took care of pier flip problems I encountered with the AP1100 and SGP.


They are correct. In fact I have both mirrored so they are both on east side.

I’m currently (at this moment) doing an experiment on this issue. When I get the results I’ll repost what I find.

Basically it has to do with SGP reporting incorrect time to flip when you are East of the meridian but outside the safe zone. This is just like a normal GEM with CW down. It is reporting 0:47 to flip when in fact the object is 1:50 from the meridian. If I click the Set button in SGP to get to the Meridian Flip settings I get the message about this mount not allowing pier flips prior to crossing the meridian and sets the Degrees Past Meridian to 0. Now SGP correctly reports the time to flip as 1:47.

My guess is that if I don’t press the Set button and leave SGP with the incorrect time to flip the flip will fail and I will get the error message. If I press the Set button and let SGP set the Degrees Past Meridian to 0 the flip will succeed.

I might be wrong, but I think this may be the source of SGP’s confusion. If APCC has West limits set in the Eastern sky, SGP will not flip. West limits should be past the meridian in the Western sky. You may want to check with @rgralak on this.

For reference, I am posting my APCC and SGP window currently running. You can see that the time to flip in SGP and APCC matches. I am running APCC and SGP 4 beta 636.

Thanks Lucam. I"m pretty sure I mirrored the limits based on AP’s video on YouTube. Anyway, here’s the result of last night’s (and early morning) tests.

Selected an object east of the meridian and outside the meridian safe limit. Mount slewed to the object, CW down. Normal. SGP reports meridian flip in 00h47m. The object, however, is ~ 1h50m east of the meridian. APCC and the V2Driver show a meridian delay of 1.1 hrs. I predicted that the flip would fail, and it did. In 47min I immediately got the error message that the flip was aborted and the log shows the error message “Telescope must be pointed across the meridian to pier flip”.

Another attempt is made selecting an object (NGC1444) also east of the meridian and also outside the meridian safe limit. Slew and guiding, CW down, normal. SGP reports a meridian flip that is again too early based on the object’s current location. However, this time I click the ‘Set’ button on the telescope dialog to bring up the meridian flip settings in SGP. SGP immediately responds with a warning message: “Your mount does not allow pier flips prior to crossing the meridian and your ‘Degrees
Past Meridian to Flip’ value has automatically been set to 0’” Clicking OK to dismiss the dialog I see that SGP is now reporting the correct time to flip. Allowing the mount to continue it indeed completes the flip and continues with no problem.

It seems to me that (maybe) SGP should be setting the ‘Degrees
Past Meridian to Flip’ to 0 automatically. I’m pretty sure even if I set the value to 0, then slew to an eastern object as above, the value gets reset to a non-zero value. Unless I go and click the ‘Set’ button before starting a sequence, flips will fail.

It’s possible I am not understanding or missing context, but this is a user setting and Im unsure why SGPro would assume to set it back to 0 if the user has specified an early flip. The only gotcha here is that your mount may not support early flipping. In this case, SGPro is supposed to throw up a warning stating as much when the sequence starts. I have just now tested this setting to make sure it is persisting and it seems OK. When I set it to a value and save the sequence, the next time I open the sequence it is still set to that value. I am unsure how yours could be resetting to a negative value every time. Even if you have a negative value in the equipment profile SGPro will never default to it without your knowledge.

I’m going to post this to the AP forums as well. There is a setting in APCC:
Send Limit to SGPro: If Sequence Generator Pro (SGPro) is running and declination changes, the current meridian delay value is sent to SGPro. SGPro can use that delay to determine how far before or after the meridian that a pier flip will occur. SGPro will only attempt to do the pier flip once the meridian delay value is reached. that may be the reason this is happening.

Ah ya, AP mounts do have some special handling.