Meridian flip Failure..Help!


Hi and thank you for reading this.

I have a Celestron C14 Edge HD on a CGE Pro mount with a Starsense HC and for some reason SGP will not Pier Flip. I’ve attached a couple of screen grabs depicting the failure message. Everything else works fine including slewing and centering on a target. Also When I manually flip the scope (SGP just won’t do it)SGP will not inform PHD2 that it flipped and it will start sending guiding commands in the opposite direction until I force a recalibration.Any ideas on settings or what I’m doing wrong?

Thank you!

Pablo Lewin


If you can attach the SGP logs when a flip is performed that would be helpful. You can find them under the Help menu in SGP.




Thank you!

Will do



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sg_logfile_20160815201003.txt (775.8 KB)


Jared, the above is one of the log files when the pier failed to flip. Thank you!

Pablo Lewin


Hi Jared, did you get a chance to look at the log file yet?


You are not able to flip because you asked the mount to flip a full 10 minutes prior to the meridian. The mount decided it was mechanically unable to reach this position from the opposite pier side so it threw an exception. Try flipping closer to or after the meridian instead of before it.

[8/15/2016 11:18:20 PM] [DEBUG] [Telescope Thread] Pier Flip failed when using side of pier: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. —> System.Runtime.InteropServices.COMException: Setting the side of pier to East cannot be done because the current position cannot be reached with the mount on that side of the pier


Thank you, I obviously gave you the last log of when I tried 10 degrees before because when I tried right at the meridian and then plus or minus 1,2,3,4,5 etc… It still wouldn’t work…any other thoughts?




Not off the top of my head. I would need to see a log where it failed with those parameters set because the error would be different.


Ken I will post them here when I get home on Monday , I’m beginning to suspect the Celestron ASCOM driver…will check on Monday and report back. Thank you for your time and help.


As well as SGP logs logs from the Celestron ASCOM driver are absolutely essential.

What I think is happening is that, because you are using a StarSense HC, pier flips before the meridian are not allowed. The StarSense HC doesn’t have the full functionality of the NexStar HC and setting the side of pier is one of the things that can’t be fully implemented.

Set SideOfPier() should work but only after the mount has crossed the meridian. If it hasn’t then the error message that’s shown in the SGP log is shown.

A driver log will show exactly what is happening, it is absolutely essential that you collect and send one that covers one of these failed flips.

Chris R


Hi Chris thank you for the reply. How do I access the Ascom log? Pretend I’m a newbie when you respond because I am! LOL!



You can find this out, and much more, by reading the driver help file. This is available by pressing the button marked Help that’s located on the driver setup form.

It was also available when you installed the driver, something that you as a newbie, can only have recently done. You must have chosen not to do so.



ASCOM.Celestron.2355.360780.txt (842.1 KB)


Chris I uploaded the ASCOM file of the same date as the sgp file…thanks!


I have another file prior to this one but this forum won’t allow me to upload on account of being too big, but I can email to you if you want.



The log file that you sent covers the period from 23:55 to 01:46, this doesn’t cover when the set pier side error that you reported happened. It look as if the previous log file may be the one that is needed

However I would expect that there will be an error. The StarSense HC will not do a pier flip before the meridian.

You must set the meridian flip to after the mount has crossed the meridian.

One thing that would help is if SGP were to keep trying when a meridian flip fails. What I’m thinking of is the mount tries to do a meridian flip, if it fails it takes the next image anyway, then, when it is finished, tries again.
It keeps trying to flip until the mount indicates that it has succeeded. This would handle the situation where the mount isn’t quite ready to flip when it’s commanded.

The StarSense has been intensely frustrating for me. It’s got such promise - no need to do an alignment by hand - but Celestron’s implementation of it seems to me to be half hearted. There are all sorts of things that the normal HC will do but the SS HC won’t do, this problem with Side of Pier is one, their failure to implement their sync command correctly is another. I have absolutely no confidence that they will ever do anything about these.

Chris R


Thanks Chris, I tried uploading the ohter file but I keep getting this here “Sorry, the file you are trying to upload is too big (maximum size is 1024KB).” The file is 1149kb. May I email it to you? and it seems to me that I may have to do away with starsense after all (I’m gonna miss it). I will try tonight to set the meridian flip to after the mount has crossed the meridian to see if it will work.
Pablo Lewin


Chris I broke the prior logfile in two so that I’d be able to upload them here. A and BASCOM.Celestron.2128.096560_A.txt (474.1 KB)


ASCOM.Celestron.2128.096560_B.txt (674.7 KB)