Problem with ASCOM pulse dithering

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howardgrams
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Joined: Thu Aug 17, 2017 7:59 pm

Problem with ASCOM pulse dithering

Post by howardgrams »

Hi Robin,

I was eager to try out your new dither-by-nudging the ASCOM mount feature of Sharpcap 4.0beta 4.0.7596.0 last evening, but had problems.

I went to Settings -> Guiding and selected Dither only using ASCOM pulse guiding, leaving the default of 20 arc seconds if using ASCOM pulse guiding. Then while live stacking I enabled Automatically Dither with a dither interval of 60 seconds. My Live Stacking involved 2 second exposures. All seemed to be going well, with me seeing status messages like Guiding Status: Guiding and Dither Status: Waiting 44.2 seconds before next dither.

When the wait count reached zero, it changed to Guiding Status: Not connected to guiding, and the status message at the top of the camera display window showed Warning: Last nnn frames have not been stacked because Live Stacking is paused - Unguided dithering using ASCOM mount is currently dithering. I finally gave up waiting after 172 frames (nearly five minutes).

The mount is an alt-azimuth mount, the iOptron AZMP, which can slew from one side of the sky to the other in about 30 seconds so it should be able to slew 20 arc seconds in only a few seconds of time.

Apparently SC is instructing the mount to slew, but does not get the message when the slew is complete. The fact that the mount is alt-az is probably significant.

Howard
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Re: Problem with ASCOM pulse dithering

Post by admin »

Hi Howard,

if you can find the log, have a lock for an entry like

Code: Select all

Random dither of (X,Y) arcsec; rates are {some info}, pulse guide times are (number, number)s
If SharpCap isn't correctly interpreting the pulse guide rate from the mount then perhaps the times that get calculated are stupidly long.

As far as I can work out that's the only way that the dither could take an unusually long time.

cheers,

Robin
howardgrams
Posts: 24
Joined: Thu Aug 17, 2017 7:59 pm

Re: Problem with ASCOM pulse dithering

Post by howardgrams »

Hi Robin,

The log shows that the AZMP ASCOM driver doesn't implement what you are sending. I had assumed that you were going to calculate a new RA/Dec position and ask the mount to reposition to that target. Can't you do that if the mount doesn't implement the PulesGuide method?

Info 20:45:47.477951 #28 Live stacking paused : Unguided dithering using ASCOM mount is currently dithering. in void SharpCap.FrameTransforms.LiveStacking.StackingParameters.Pause(string reason)
Info 20:45:47.480953 #28 Guiding SettleState changed to Dithering in void SharpCap.Base.Guiding.GuidingBase.set_SettleState(SettleState value)
Info 20:45:47.486951 #35 Random dither of (9.36,18.72) arcsec; rates are {X=0.004166667, Y=0.004166667}, pulse guide times are (0.624,1.248)s in void SharpCap.Models.DitherOnlyGuiding.Dither(float ditherPixels, bool raOnly, float settledPixelOffset, float minSettle, float maxSettle)+() => { }
Error 20:45:47.510952 #35 Could not dither : Exception of type 'MethodNotImplementedException' : Method PulseGuide failed. is not implemented in this driver.
Stack Trace: at void ASCOM.DriverAccess.MemberFactory.MethodTargetInvocationExceptionHandler(string memberName, Exception e) in C:/ASCOM Build/Export/ASCOM.DriverAccess/MemberFactory.cs:line 676
at object ASCOM.DriverAccess.MemberFactory.CallMember(int memberCode, string memberName, Type[] parameterTypes, params object[] parms) in C:/ASCOM Build/Export/ASCOM.DriverAccess/MemberFactory.cs:line 422
at void ASCOM.DriverAccess.Telescope.PulseGuide(GuideDirections Direction, int Duration) in C:/ASCOM Build/Export/ASCOM.DriverAccess/Telescope.cs:line 757
at void SharpCap.MountProxy.ASCOM.MountInterceptionProxy.PulseGuide(GuideDirections direction, int duration) in C:/Documents/Source Code/SharpCap/src/SharpCap.MountProxy.ASCOM/MountInterceptionProxy.cs:line 170
at void SharpCap.MountProxy.ASCOM.MountWrapper.PulseGuide(GuideDirection direction, int durationMs) in C:/Documents/Source Code/SharpCap/src/SharpCap.MountProxy.ASCOM/MountWrapper.cs:line 692
at void SharpCap.MountProxy.ASCOM.RefreshMountProxy.PulseGuide(GuideDirection direction, int durationMs) in C:/Documents/Source Code/SharpCap/src/SharpCap.MountProxy.ASCOM/RefreshMountProxy.cs:line 254
at void SharpCap.Models.Mount.Nudge(float rate, float dx, float dy) in C:/Documents/Source Code/SharpCap/src/SharpCap/Models/Mount.cs:line 397
at void SharpCap.Models.DitherOnlyGuiding.Dither(float ditherPixels, bool raOnly, float settledPixelOffset, float minSettle, float maxSettle)+() => { } in C:/Documents/Source Code/SharpCap/src/SharpCap/Models/DitherOnlyGuiding.cs:line 138 in void SharpCap.Models.DitherOnlyGuiding.Dither(float ditherPixels, bool raOnly, float settledPixelOffset, float minSettle, float maxSettle)+() => { }
Error 20:45:47.511952 #35 Inner Exception : ASCOM.MethodNotImplementedException: Method PulseGuide failed. is not implemented in this driver.
at void ASCOM.iOptron2014.Telescope.PulseGuide(GuideDirections Direction, int Duration) in void SharpCap.Models.DitherOnlyGuiding.Dither(float ditherPixels, bool raOnly, float settledPixelOffset, float minSettle, float maxSettle)+() => { }
Info 20:45:47.511952 #35 Guiding Connection state changed to False
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Re: Problem with ASCOM pulse dithering

Post by admin »

Hi Howard,

there's nothing stopping an implementation in terms of small GOTO movements, I just chose to use the other option of pulse guiding when I sat down and wrote the code. It turns out that I got the test for whether the mount can pulse guide or not wrong, which is why you managed to get as far as you did - you should have been stopped right at the start with a message telling you that your mount cannot pulse guide :(

Right now I'm going to correct the pulse guide available logic and then put the goto version onto the todo list - it's moderately complicated.

cheers,

Robin
howardgrams
Posts: 24
Joined: Thu Aug 17, 2017 7:59 pm

Re: Problem with ASCOM pulse dithering

Post by howardgrams »

OK, thanks Robin.

Howard
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