V4 dithering not working

Questions, bug reports, requests for enhancements, etc.
iMustBcrazy
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Re: V4 dithering not working

Post by iMustBcrazy »

Peter Polakovic wrote: Wed Jul 07, 2021 8:43 am Well, result is really not bad.
maybe another problem as the guiding seemed to be disturbed by me disconnecting and reconnecting to the agent.
It shouldn't affect it. AG is just a configuration and monitoring tool for guider agent. But true is, that it makes server busy with uploading the images.
probably won't have a clear night until Saturday so I can only do more testing then. Thanks
iMustBcrazy
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Re: V4 dithering not working

Post by iMustBcrazy »

I almost forgot about this because of other problems but dithering is still only happening in one direction. I don't use ST-4 cable so it can't be a bad connection. Here is a stack with no star alignment - so just stacked raw frames out of the camera - showing dithering is only in one axis (RA I think).

It would be nice if someone can show this working in V4 using remote agents on RPi. Thanks
dither_stack_no_star_align.jpg
dither_stack_no_star_align.jpg (25.05 KiB) Viewed 192 times
JohanB
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Re: V4 dithering not working

Post by JohanB »

Hi,

I think it works fine with me; using remote agents on an RPi, guider agent uses Mount Synscan, with a AZ-EQ6. Set dither preference to 2px.

Made a blink video; https://www.dropbox.com/s/f47omw4i0zk52 ... 7.mp4?dl=0

Regards, Johan
iMustBcrazy
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Re: V4 dithering not working

Post by iMustBcrazy »

JohanB wrote: Thu Jul 29, 2021 4:29 pm Hi,

I think it works fine with me; using remote agents on an RPi, guider agent uses Mount Synscan, with a AZ-EQ6. Set dither preference to 2px.

Made a blink video; https://www.dropbox.com/s/f47omw4i0zk52 ... 7.mp4?dl=0

Regards, Johan
Cool video - Thanks Johan, its really good to get confirmation. The bad news is that maybe I have an equipment problem! ;-(
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Peter Polakovic
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Re: V4 dithering not working

Post by Peter Polakovic »

Pls. can you share a small subframe of single frame with some stars in a full resolution? I have s till a feeling, that the problem is not dithering, but either drift or field rotation.
iMustBcrazy
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Re: V4 dithering not working

Post by iMustBcrazy »

Peter Polakovic wrote: Thu Jul 29, 2021 8:22 pm Pls. can you share a small subframe of single frame with some stars in a full resolution? I have s till a feeling, that the problem is not dithering, but either drift or field rotation.
Sure. in the dropbox link is a section (at 400%) of one sub (240secs) in the middle of the capture session. The the guiding doesn't look that bad but the guiding error looks to be in the same axis as the dither - I was expecting it to error on the axis that is NOT dithering :-s

Also, you'll find a video similar to Johan's that shows the each sub in sequence and you can see the dithering is always along the same axis (RA - no DEC movement)

https://www.dropbox.com/s/f8yv9f0akamdq ... M.png?dl=0

https://www.dropbox.com/s/9yy8p4le6ked8 ... M.mov?dl=0
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Peter Polakovic
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Re: V4 dithering not working

Post by Peter Polakovic »

Well, yes, it really looks like the dithering works only in one direction, no idea why. Can you check "ST4 guide rate" property on SynScan device? Maybe it is asymmetric for some reason.

Nevertheless, the trails on the final images are apparently not related to dithering. Even on the single frame is clearly visible the star elongation. Maybe the mount doesn't guide in one direction at all.
iMustBcrazy
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Re: V4 dithering not working

Post by iMustBcrazy »

I'm checking back to over 1 year ago - don't know if this was v3 or v4 but likely v3 - and I see the same problem exists. But how can calibration pass and yet not be able to guide or dither? Successful calibration would prove that the guiding control loop is working on the mount.
iMustBcrazy
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Joined: Sun Jun 02, 2019 3:52 pm

Re: V4 dithering not working

Post by iMustBcrazy »

Hi Peter,

I recorded guiding during a capture session but for some reason there is only a few seconds in the CSV file. But here is the indigo log of my whole session last night that shows auto focus attempts and guiding attempts. I hope you can make something out of it. Here is the link:

https://www.dropbox.com/s/bgpflpnnb5oxd ... g.zip?dl=0

Thanks
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Peter Polakovic
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Re: V4 dithering not working

Post by Peter Polakovic »

I'm checking back to over 1 year ago - don't know if this was v3 or v4 but likely v3 - and I see the same problem exists. But how can calibration pass and yet not be able to guide or dither? Successful calibration would prove that the guiding control loop is working on the mount.
Well, it may happen. If the guider scope axis is far enough from main scope axis you may have field rotation and trails even with a perfect guiding as en effect of bad polar alignment. Also calibration can succeed but the guiding can be poor e.g. if the setup is not properly balanced.
I recorded guiding during a capture session but for some reason there is only a few seconds in the CSV file. But here is the indigo log of my whole session last night that shows auto focus attempts and guiding attempts. I hope you can make something out of it.
I see the problem (at time 02:54:10.371923), but I don't understand the reason. Maybe the guiding star was lost, but in one moment was the guiding settling down after dithering and in couple of seconds later it was out of control:

02:54:06.618314 indigo_server: 'Guider Agent'.'AGENT_GUIDER_STATS' NUMBER ro Ok 2.0 0 (null) {
02:54:06.618342 indigo_server: 'PHASE' = 0
02:54:06.618370 indigo_server: 'FRAME' = 522
02:54:06.618395 indigo_server: 'REFERENCE_X' = 0
02:54:06.618420 indigo_server: 'REFERENCE_Y' = 0
02:54:06.618445 indigo_server: 'DRIFT_X' = 0.348
02:54:06.618471 indigo_server: 'DRIFT_Y' = 0.17
02:54:06.618496 indigo_server: 'DRIFT_RA' = 0.357
02:54:06.618521 indigo_server: 'DRIFT_DEC' = -0.151
02:54:06.618546 indigo_server: 'CORR_RA' = -0.222
02:54:06.618571 indigo_server: 'CORR_DEC' = 0.091
02:54:06.618596 indigo_server: 'RMSE_RA' = 0.348
02:54:06.618621 indigo_server: 'RMSE_DEC' = 0.185
02:54:06.618647 indigo_server: 'SNR' = 20.4364
02:54:06.618672 indigo_server: 'DELAY' = 0
02:54:06.618697 indigo_server: 'DITHERING' = 0.348
02:54:06.618721 indigo_server: }
...
02:54:10.371923 indigo_server: 'Guider Agent'.'AGENT_GUIDER_STATS' NUMBER ro Ok 2.0 0 (null) {
02:54:10.371950 indigo_server: 'PHASE' = 0
02:54:10.371976 indigo_server: 'FRAME' = 523
02:54:10.372001 indigo_server: 'REFERENCE_X' = 0
02:54:10.372026 indigo_server: 'REFERENCE_Y' = 0
02:54:10.372052 indigo_server: 'DRIFT_X' = -128.28
02:54:10.372078 indigo_server: 'DRIFT_Y' = -0.201
02:54:10.372104 indigo_server: 'DRIFT_RA' = -128.115
02:54:10.372129 indigo_server: 'DRIFT_DEC' = -6.513
02:54:10.372153 indigo_server: 'CORR_RA' = 1
02:54:10.372178 indigo_server: 'CORR_DEC' = 1
02:54:10.372204 indigo_server: 'RMSE_RA' = 57.296
02:54:10.372229 indigo_server: 'RMSE_DEC' = 2.918
02:54:10.372255 indigo_server: 'SNR' = 15.7275
02:54:10.372279 indigo_server: 'DELAY' = 0
02:54:10.372305 indigo_server: 'DITHERING' = 57.296
02:54:10.372328 indigo_server: }

But I can't imagine the drift X can be really -128 with window size 8, so it looks like some nasty bug :(
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