Celestron CGE and SPG Meridian Flip Woes

Continuing the discussion from Meridian Flip Fail:

Hi Guys,

SGP works flawlessly for me especially the plate solving, it’s amazing. I have a Celestron CGE mount but I can’t get the mount to flip. Sometimes SGP thinks the mount has flipped (But Hasen’t) and SGP starts to plate solve thinking it’s on the other side and then stops when it realizes that the mount has not flipped.

The Celestron CGE does have a hard stop right at the meridian I just can see what I’m doing wrong. Is there anybody doing the flip with a CGE mount that could walk me through this?


I had the same issue, when you try to flip at exact meridian, sometimes it succeeded and sometimes it failed …
I needed to set the flip at 1 degree past + the wait option, since then I had no failed flips. My guess is that the mount needs to be over meridian before it actually flips when SGP sends the slew command, otherwise it stays at current position.

What HC version are you using? And what version of the ASCOM driver?

The way Pier side is implemented depends on this. Earlier versions don’t have pier side control and will only flip once the mount is past the meridian.

AIUI the CGE can go a few degrees past the meridian - 6 degrees I think - and the simplest way to flip will be to do so when the OTA is a degree or so past the meridian.

If you try to flip exactly on the meridian then small differences in the alignment may mean that the mount thinks it’s not past the meridian and won’t flip.


Hi Chris,
Thank you for your very informative reply, it was very appreciative. I have now upgraded everything that I can with the gear that I’m using. I am hoping that I can get out tonight (Weather permitting) to give this a try.

Is there a way to test a meridian flip during daylight hours?


Yes and no. You can’t test it completely unless you can fake out the plate solver, which you can’t do. However if you’re more worried about your mount reaching and flipping then yes you can test that.

  • Disable the “Auto Center” option in the meridian flip dialog
  • Set the auto guider to none, or run PHD in sim mode.

Hook up your scope and walk through whatever you want to simulate. You can also get near the meridian and click the “Run” button next to the :“Use Auto Meridian Flip” text in the Telescope control panel to attempt to invoke a meridian flip manually.

Also the information displayed on the telescope control panel can be very helpful when attempting to figure out why flips aren’t working:

In particular the “Time to Meridian” is very helpful. If will display a negative number when your scope is past the meridian. Also if this shows “NA” then it means that it thinks you don’t need a meridian flip as your scope is on the West side of the mount (looking east)

Hope that helps,

Thanks Jared but I don’t seem to see the “RUN” button beside the “Use Auto Meridian Flip” All I see is the “Set” button
Although I am not very computer literate, I have managed to get the plate solving working to a very high degree of accuracy every time. Being able to do a Meridian Flip would make life so much easier


I’m not sure how you could miss it…it’s literally right next to that button:

Do you happen to have font scaling turned on? Maybe it’s pushing things around.


OK Thanks Jared. I guess I had been looking at the same Meridian Flip Dialog box in the Equipment Profile area that does not show the “RUN” feature. I found the other telescope dialog box under the control panel and found the “RUN” button but it seems to be grayed out and not active.

Ah. The profiles are used only to save data for reuse. If you want to modify settings that will be used immediately then the Control Panel is the place to do it. Think of the Equipment Profiles as templates and Sequences as using those templates.

If it’s grayed out then you may need to uncheck the “Auto Center” option that I mentioned above which can be found in the meridian flip settings on the control panel.


Hi Jared,

Thanks for your response. Everything seemed to respond as per your instructions. The mount flipped after pushing the “RUN” button when the mount came close to the meridian. Does this mean that the mount is capable of flipping through SGP durring a sequence with the correct settings? or could there be another “Gottcha” somewhere in there?

Cheers and have a great weekend!!

Did it work?! :slight_smile:

Sadly it did not work. I did manage to manually flip the mount by hitting the run button but when it came to field operation the mount failed to flip. I have been trying to get this to work for weeks albeit some nights the clouds would roll in after just an hour or so of testing.

The other night I was working on the flip I managed to get a very strange message saying that the CGE was unable to perform a flip! My first though was why did it take 4 weeks to finally tell me that!! I don’t think that’s the case but I as starting to ask everywhere I can.

My set up is to connect SGP to the latest Celestron driver and my planetarium program is The SKY6. I connect The SKY6 to the mount using the API driver. Not being very computer savvy, I just wonder if the driver that controls the mount from The SKY6 is causing any of the problems.

The Celestrom CGE mount can cross the meridian by only about 1.5 degrees and then does a hard stop. From the telescope control dialog box in SGP when the time to flip occurs, the “Plate Solve” dialog box comes up and syncs the mount OK and then there is a few second pause and I get that dreaded red “X” that tells me that the mount failed to flip.

One strange thing that happens is that after the mount fails, as above, I will go right back to the SKY6 and pick another target close to the meridian. Sometimes, even though the star I chose is on the east side of the meridian the mount starts to slew to the west side of the pier and try to get to my target from the opposite side of the pier. After that the mount has no idea where it is and I have to restart the mount.

So that’s where I am now, still working on it!!


I still need an answer to what HC type and version you are using. There are 4 possible HC types, each with their own version. “The Latest” tells me nothing.

What is the API driver? You can’t connect TheSky using it’s own driver and connect SGP at the same time.

I would take TheSky out of the picture, it could be interfering.

It’s easy to test the mount pointing state behaviour using various simulators for imaging and disabling plate solving. Do a quick align to set the mount.

There’s nothing more I can suggest without the information I’ve asked for.


Hi Chris,

I don’t use the Celestron HC but I use NexRemote version 1.7.22. The mount firmware is 4.21 and the ASCOM driver for the Celestron is 5.0.30. The version of SGP is

I am able to try things again tonight and I will take The Sky6 out of the loop.

Thanks, that tells me that NexRemote is emulating a 4.21 HC.

I’ve had a look with NR and it looks as if the Ra Limits and Meridian Mode options are not available in the HC for the CGE, even though they are for the other GEM mounts with that HC version.

I’ve just run Conform with this mount and the driver is aware of this. It can’t set the side of pier. It will be inferring the pier side and destination pier side from the hour angle.

The only way to change to the other pier side will be to do so in the narrow band where the mount has moved past the meridian but before it has reached the hard stop.


One thing, I never used Nexremote when I had a CGEM.  I'd do a quick alignment using my hand controller and run inside.  From there, ASCOM could take care of everything else such as parking to the 'home' position.  Perhaps skipping Nexremote is the way.

I doubt that using the real HC will make any difference. NR emulates the HC and runs exactly the same code as runs in the HC. I guess that the problem is that there is a narrow window between the mount crossing the meridian and it running into the hard stop. The location you are slewing to must be past the meridian to do the flip and set up errors mean that you probably need to be a bit past to be confident that a slew will change the pier side. If the mount will only track for 1.5 degrees past the meridian that’s 6 minutes and if you wait until it’s 0.75 degrees past before flipping then there’s only 3 minutes tracking left.

Maybe the way to operate is to plan to image until the object is close to the meridian, then move to a different object that’s not near the meridian and image that while the first object gets past the meridian, then move back to the first object once it’s past the meridian.