Plate solve 2 does not center

Since the past few days, I am having trouble getting Platesolve2 to center a target. It seems that it gets close but not within the specified 50 pixels.

A log file is available at the link below. Please help.


Use ASTAP its much better

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Hi Shailesh

Have not looked at your logfiles but wonder if you have the same issue as this thread i.e. confusion over JNOW versus J2000 coordinates.

I assume from your post that you have managed successful centering in the past so maybe something has been accidently changed.

I also agree with Nocturnalguy that ASTAP is very good and quick solver but solving may not be your problem.

Where should I check Jnow vs J2000 ?

Hi Shailesh,

I’ve taken the time to have a look at your logfile. I think that the previous suggestions are off the mark and that your problem is most likely due to a cable jam or other problem that was preventing your mount/scope from moving freely to correct the measured centering error between your requested target position and the scope’s actual position as identified by Platesolve.

As evidence I see the following entries in your log-file:

[02/06/21 20:39:45.344][INFO][Center Scope Thread][SQ;] Retrying auto center. Total Error > Allowable error: 1888.1 > 50.0
[02/06/21 20:39:45.344][INFO][Center Scope Thread][SQ;] RA Error: 1701.0
[02/06/21 20:39:45.344][INFO][Center Scope Thread][SQ;] DEC Error: 819.5

[02/06/21 20:40:30.664][INFO][Center Scope Thread][SQ;] Retrying auto center. Total Error > Allowable error: 1888.7 > 50.0
[02/06/21 20:40:30.664][INFO][Center Scope Thread][SQ;] RA Error: 1701.6
[02/06/21 20:40:30.664][INFO][Center Scope Thread][SQ;] DEC Error: 819.6

[02/06/21 20:40:53.286][INFO][Center Scope Thread][SQ;] Retrying auto center. Total Error > Allowable error: 1889.0 > 50.0
[02/06/21 20:40:53.286][INFO][Center Scope Thread][SQ;] RA Error: 1701.9
[02/06/21 20:40:53.286][INFO][Center Scope Thread][SQ;] DEC Error: 819.8

I believe that the values 1881.1, 1888.7 and 1889.0 are the error displacements in arc-secs between your requested and current position (which obviously you can check if you know the resolution of your scope/camera in arc-secs per pixel) but in all three cases these are presumably greater that your target error limit of 50 pixels.

However the minute differences between these three error displacements are so minute that I think the only feasible explanation is a mechanical issue (such as cable jam) that has prevented your mount from achieving the requested correction, I therefore recommend you carefully check your mount’s ability to move freely at around the position it would have been in at the time of your centering attempts.

Later in the log I also see a further error message about a failure of the mount to sync. I’ve no idea what has caused this or if it is just a simple consequence of the failed centering issue.

[02/06/21 20:41:15.731][DEBUG][Telescope Thread][SQ;CE;] Telescope: Sync behavior set to “Sync”…
[02/06/21 20:41:15.731][DEBUG][Telescope Thread][SQ;CE;] Telescope: Sync Passed in J2000 but mount requires JNOW, converting…
[02/06/21 20:41:15.731][DEBUG][Telescope Thread][SQ;CE;] Telescope: Syncing to JNOW RA: 5.6578175401372 Dec: -5.76130549198877
[02/06/21 20:41:15.802][DEBUG][Telescope Thread][SQ;CE;] ASCOM Telescope: Error in Sync : CheckDotNetExceptions
[02/06/21 20:41:15.802][DEBUG][Telescope Thread][SQ;CE;] Auto center failed! Failed to sync the telescope!

Platesolve in this situation is just reporting your current pointing position. It has no influence on your mount’s ability to respond to the corrective changes requested by SGP. Irrespective of whether or not ASTAP is better than Platesolve is not going to help here. Also I think my comment about J2000/JNOW coordinates is off the mark.

Hope this analysis helps.


Thank you, MIke.

I will double-check the mount. Interestingly The Sky X closed loop slew works, so I am unsure what is going on.


Hi Shailesh,

I do not use The Sky X so am not familiar with how it works but if you cannot find any mechanical issue preventing free movement of the mont then I can only think that there is a sync issue between where the mount thinks it is pointing and where it is actually pointing as determined by platesolving a downloaded image.

If the mount believes it is already correctly pointing to the requested RA/DEC position then would that reasonably explain why it barely moves when re-requested to move to the exact same position? Is there a process/option for resyncing the pointing model with the current position? What results if you change the Telescope/Sync Behaviour to a different option? Are you using the recommended option? Is it necessary to recompile your pointing model?

Good lucl sorting this issue


I assume you have had your imaging rig has been working correctly in the past so has anything recently been changed?

Hi Shailesh,

What mount are you using?
Are you using The SkyX as an ASCOM-Driver?
Do you have a pointing model?

Kind regards,

Hi Mike,

Thanks for your ongoing mind share. Last night I redid the Tpoint model. No difference.

There is an option in the Ascom driver to not allow sync to preserve the Tpoint model but I get a warning from SGP which said target may not center so I changed it back to sync checked.

I am not sure what changed, so I am left scratching my head.

As before the Closed Loop Slew in TSX centers the object (Orion Nebula).

Not only does PS2 fail, it fails after 5 tries, whereas in the past I was able to plate solve in the first try.

I am left scratching my head. I have also posted in the Software Bisque forum, but they are not familiar with SGP, as this forum is.


Reporting back. I changed the Sync Behavior in the telescope CP from Sync to Target Offsets and now I am able to plate solve.

This is strange because I had not changed it and would work previously.

@Horia I use the Paramount MX mount, and yes use the Ascom driver for TSX, and yes I have a Tpoint pointing model.


Hi Shailesh,

Perfect, you solved the problem.

When working with a Paramount, The SkyX - in the newer versions - will simply drop a Sync command. This is because in this configuration Software Bisque does not want a Sync to corrupt the pointing model. So the solution is to use Target Offset instead of Sync for the centering function in SGP.

You could also try to get such a good pointing model that you will always hit the target without other corrections. Depending on your setup, this may not be feasible.

Kind regards,

Hi Horia,

Thanks for your reply.


Do you know this for a fact from someone in the Software Bisque team?