Meridian flip - SGP vs Me

I suspected my G11 would meridian flip around midnight last night and since I was still up, I decided to pause the sequence between frames and use the controller to force a flip. That worked well and I resumed SGP after a re-centered and it continued just fine. However, I woke up this morning to find the mount parked and an error message that the meridian flip had failed - around 2am - long after I went to bed. It took a single frame with a new filter that was way off target before it failed. It looks like it might have decided to flip after a set of frames regardless of the fact the mount was already on the correct side of the pier.

Doesn’t SGP check pier side before performing a flip? Or is it bad practice to force a flip mid-sequence?

I know from previous posts that mounts treat flipping in a variety of ways. Some only need a slew command (to where they already are) when past the meridian to cause a flip. Others have implemented the ASCOM sideofpier. If you consider the mechanics, there is scope for ambiguity - do you use the RA or DEC to work it out for instance? I am guessing you have added further confusion by flipping the mount external to SGP. This has the potential for SGP to think it knows the state but it is wrong-footed. I may be entirely wrong but the evidence is this is exactly what I see when I fiddle with PHD2 outside of SGP when a sequence is running.

If you let SGP just do its thing. Does it cause the Gemini to flip correctly?

The issue isn’t a normal flip through SGP, that usually works fine at whatever time I set past meridian. In this case, I just wanted to move up the flip to occur while I was standing by the mount. I assumed SGP would query the mount before executing its flip and recognize the mount was already on the correct side of the pier. It appears that’s not the case and SGP went ahead and flipped at the time it calculated the mount would have been past meridian by the time I normally have set. I wasn’t out there when it happened so I don’t know where it tried to flip the mount to.

If I do this in the future, I guess I have to go into the control panel and turn off automatic flip. But that’s a risky thing to do if it stores that setting and I forget to turn it back on the next time I image. It would make a lot more sense (to me), for SGP to ask what side of the pier the mount is on at the time it is supposed to flip and only execute the flip if it’s needed. I do understand that not all mount report side-of-pier, and, frankly, I don’t know if my G11 is one of those.

Yes, SGP does exactly this and if a flip isn’t needed it shouldn’t have attempted to execute one. The G11 Gemini 1/2 both implement SideOfPier as well.

Where were you imaging? Were you under the pole by chance? Do you have logs?

Thank you,

Jared, I was imaging M13.

Here is, I think, the log file for that night. It shows a meridian flip failure around 2am.

Looking through the log file, I see that SGP does continually check for side-of-pier and whether a flip is required - that’s great. However, in this case, I had manually performed a flip through the controller during a pause in the sequence. The log shows the telescope being on the West side of the pier until arpound the time I manually flipped it, as expected, then it shows it being on the East side of pier, as expected. Then around 2am it decides that the telescope, being on the East side, should be flipped, but that makes no sense since it would put the telescope back on the West side.

There are a lot of errors coming from PHD2 just prior to this. So I’m guessing something happened with your mount or it got into a confused state:

 [07/04/20 02:01:21.428][DEBUG][PHD2 Listener Thread][SQ;] Unknown object from PHD2: {"Event":"Alert","Timestamp":1593853281.424,"Host":"LENOVO-PC","Inst":1,"Msg":"PulseGuide command to mount has failed - guiding is likely to be ineffective.","Type":"warning"}

We directly ask the mount of the side of pier in the case of the Gemini. So I’m guessing whatever caused the issue with the guiding likely also caused the issue with the flip:

[07/04/20 02:01:24.645][DEBUG][Sequence Thread][SQ;] Checking if Meridian Flip is needed
[07/04/20 02:01:24.829][DEBUG][Sequence Thread][SQ;] Telescope is on the West side of the mount
[07/04/20 02:01:24.830][DEBUG][Sequence Thread][SQ;] Meridian Flip needed, Hour Angle >= Degrees Past To Flip: 86.7083333333333 >= 11.25