Slew to target error

Hi, I am setting up for a night of imaging m82 and pulled up my previous sgf profile for this object from last night. I had previously plate solved and used that for my target location in the “Target Settings” dialog. With everything connected and running as expected (mount, camera, etc…) when I press the “Slew Now” button to slew to the saved target coordinates nothing happens. I looked in the error log and see the below lines. Nothing else is there since I just started up SGP and connect everything.

I am running the RC3 release of 2.4:

[3/9/2015 8:53:58 PM] [DEBUG] [Main Thread] Slewing to target…
[3/9/2015 8:53:58 PM] [DEBUG] [Telescope Thread] Slew telescope message received…
[3/9/2015 8:53:58 PM] [DEBUG] [Slew Monitor] Waiting for slew to complete…
[3/9/2015 8:53:58 PM] [DEBUG] [Telescope Thread] ASCOM Telescope: Error in Slew : Object reference not set to an instance of an object.
at ah.Slew(TelescopeInformation tp)
[3/9/2015 8:53:58 PM] [DEBUG] [Telescope Thread] Slew complete…
[3/9/2015 8:53:58 PM] [DEBUG] [CP Update Thread] Error in control panel UI updater: Object reference not set to an instance of an object.

If you need any more info or the the rather short error log, let me know. I can slew via the hand control and the “Center Now” function seems to work.


A quick test in the simulator shows no problem with that sequence of steps. The mount slews just fine. Are you using a dome? Can you share the SGF file?

Can you reproduce this consistently?

Also , the full log is always best to attach. We often need to look for things not reported in the vicinity of the error.

I am not using a dome. I am in a middle of a sequence now, so I cannot test. Looking at my notes, I also see this happened last night too. But I did also have an issue with doing a “center now”, it failed on the scope move part. I disconnected from my mount via the button and reconnected. Then the center now worked.

Here is tonights full log, the errors happened at the beginning of the log.

Last nights log:

Here is the SGF file:

I do know I have never had this issue in the past year of using SGP.

Thanks. What version of SGPro had you been using prior to RC3?

Also… when you have time and can figure out of this is reproducible, we can deliver a special build to trace the problem more effectively (assuming you get the same behavior every time).

My last imaging runs when I know this feature was working was on 2/10(2.4.0 build 2696) and 2/23(2.4.0 build 2740). I always upgrade when a new version is available. I have not upgraded any other software/drivers/ASCOM between now and then.

I run out of a roll off observatory so I will be able to test tonight regardless of skies. I will try to reproduce this using my normal workflow and will let you know.

I have just experienced the exact same issue tonight with RC3 (v2.4.0.2768). My logs show the same error as above (I’ll post the complete log file soon). I too was using a previous sequence. When I tried to slew to the target coordinates nothing happened. The log indicated:

[Telescope Thread] ASCOM Telescope: Error in Slew : Object reference not set to an instance of an object.

I also created a new sequence and again the slew failed.

I downgraded to and the slew worked fine. I am not using a dome.

Logs to follow shortly after I’ve packed all my kit away :wink:


Here’s the complete log file showing the slew error:


So is it fair to say you can reproduce this at will?

I found how to reproduce this… it only occurred when the telescope was selected by a profile.

Thanks, Ken. I’ll test the fix out later with my sequence.

Note that the error also occurred when doing a ‘Center Now’. The plate solving part worked fine but failed when trying to slew to correct the offset. Hopefully your ‘slew’ fix addresses this too.


RC4 working perfectly! Thanks Ken for the quick turnaround!


I installed RC4 and tried again after getting my initial sync done and it did not work. Scope still sat there. I went over to the telescope tab in the control panel and saw the that it was reporting the mount was parked (it said “unpark” on the button.). The mount was tracking, so not parked. So I pressed the unparked button and then the “slew now” button worked. Just to be clear, this is in the sequence panel in the target list in the target settings that I am doing this. It seems that SGP picked up the wrong state of the mount.