Problems platesolving using The Sky X

I hope someone will be able to help with my problem.
Until a few weeks ago, I was successfully using SGP, The Sky X Pro,and Platesolve 2 to image. I had the Sync Behaviour set to Target Offset. My mount is a Paramount ME which I operate remotely.
Then, for no apparent reason, there was a deterioration in the platesolve and centering with the centering accuracy often being significantly above the 100px which I had been using successfully (sometimes going as high as 800 px). I had it set to try to solve and centre 10 times. The platesolve found a match quickly but the error would change little after the first iteration and the solve and centre would often fail. Also, the meridian flips failed on several occasions, presumably because of poor centering accuracy.
The mount was checked physically and seemed to be fine in its motions and gear engagement.
I then uninstalled and reinstalled the Sky X in the hope that would remove the problem.
Unfortunately, problems have continued. Using Platesolve 2 the errors in centering continues to be very high. I have managed to run a sequence using Astrometry.Net which is centering more accurately. However, it is not possible to do a meridian flip. The time to flip indicator in SGP on all objects is more the 66 hours!
Has anyone experienced the same or a similar problem? I would welcome any advice on how to overcome it.
A link to the sg logfile is given below.

Thanks for looking


You might want to check things like your coordinates, time of pc/mount vs actual time etc

Thank you for the suggestion. I had already checked those and all seem OK.


It may not be the only issue, but your SkyX driver is throwing so many errors that it’s hard to see what else is going on. Have you modified or updated TheSkyX recently? Sentences that start with things like Until a few weeks ago, I was successfully using SGP almost always point to a change in environment. If you have not updated, modified or changed settings recently, it seems like the first step is to completely uninstall and reinstall TheSkyX to force reinstallation of TheSkyX ASCOM driver.

Hi Ken,
As I said in my original post, I have uninstalled and reinstalled The SkyX in the last few days because I was starting to get repeated errors in centering. What I describe is after the reinstallation. Unfortunately, I cannot put my finger on anything I changed as a cause of the deterioration prior to the reinstall. One night it just started to be less accurate than the 100px error I had been using since the equipment was set up in Spain (I live in the UK.) and got worse from there.

Well, that’s unfortunate… Maybe somebody else is having the same issue and can chime in. As it stands right now, it seems SGPro cannot communicate properly with TheSkyX

Do you have a pointing model? Have you made any changes to your pointing model?

Thanks for your message
I do have a pointing model but it has not been changed. In fact I hope that a colleague will be running a new model tonight, to see if that improves things.

I have in the past couple of months done several new pointing models, along with a lot of changes to my PA since I am now running completely unguided, exposures up to 5 minutes. I get terrible results if I use the pointing model to try to improve the guiding so I don’t use it. May be my misunderstanding of some aspects of the MEII pointing model software. I will be trying again when I return from my trip through Spain, where I am now.

Possibly related to your problem, for a long time, at least a year and maybe for the two years I have had the MEII my PS2 platesolve/centering has had the following irritating behavior:

  1. initial slew gets to within X pixels of target, X is better the better my pointing model is. The last one with 50 points and before I did PA adjustments (which screws the model up) got me to about 500 pixels (.70 arcsec/pixel).
  2. The first correction slew either takes me to less than my 30 pixel request, or the 30-50 pixels area. If it is in the > 30 area, it almost never gets any closer with additional tries, therefore I have set the tries to 3 to not waste any time.
  3. After the 1 minute wait and the do again goes, it always zeroes right in to about 1 pixel.

Weird. I sure wish I could resolve this. Seems somewhat similar to your problem.


To be as specific as possible, your TheSkyX ASCOM driver is emitting an error when SGPro attempts to access its SiderealTime property.

[10/06/19 21:00:06.503][DEBUG] [CP Update Thread] ASCOM Telescope: Error in GetLst : CheckDotNetExceptions ASCOM.SoftwareBisque.Telescope SiderealTime Get System.ArgumentNullException: Value cannot be null.

I have also seen this behaviour and it happens due to a persistent bug in the centering procedure. I have created a new topic to show the details:

Kind regards,

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