QHY 174 GPS Calibration LED issue // USB Traffic weirdness

[admin]

Hi Jean-Francois,

thanks for the suggestion of running the script. I had to take out the initial calculated values as they just don't work in my setup, but once I had taken out that block of code to just leave the search for the best values, it worked nicely, finding accurate values near to my original values of start=103000, end=31000.

What I really don't know if is the massive differences are just USB2/3 or something more.

Robin

Code: Select all

Date: Sat Nov 14 19:55:52 2020
GPS Frame Control
GPS Calibration LED on/off  : On
GPS Freq Stabilization      : Off
GPS                         : On
Rectangle Selection         :  {X=184,Y=151,Width=745,Height=1046}


Time sequence  [ms] : [160, 320, 640]


Exposure Time:  160  ms
=================================

Digit position selection:   10000 1000 100 10
Cal_Start_Pos list:  [92500L, 101500L, 102400L, 102490L, 102500L, 102510L, 102600L, 103500L, 112500L]
92500      4.396
101500      4.310
102400      4.555
102490     40.208
102500     44.546
102510     49.227
Break
Min / Max  :  4.310   49.227
Half height: 26.768

102445    20.7610
102456    25.3241
102461    27.5368
102467    30.0821
102490    40.2080
102500    44.5456

Optimisation: n = 6, k = 106.821643, m =  24.539296, Cal Start Pos = 102470

Digit position selection:   1000 100 10
Cal_End_Pos list:  [29300L, 30200L, 30290L, 30300L, 30310L, 30400L, 31300L]
29300     71.927
30200     70.521
30290     45.873
30300     41.690
30310     37.173
30400      5.222
31300      4.464
Min / Max  :  4.464   71.927
Half height: 38.195

30290  45.873471
30300  41.690377
30305  39.714942
30310  37.172518

Optimisation: n = 4, k = 119.423221, m =  10.905738, Cal End Pos = 30301


Exposure Time:  320  ms
=================================

Digit position selection:   10000 1000 100 10
Cal_Start_Pos list:  [92470L, 101470L, 102370L, 102460L, 102470L, 102480L, 102570L, 103470L, 112470L]
92470      4.906
101470      4.957
102370      4.885
102460     27.591
102470     32.117
102480     36.634
102570     72.320
103470     72.402
112470     72.473
Min / Max  :  4.885   72.473
Half height: 38.679

102460    27.5907
102470    32.1170
102480    36.6339
102485    38.7138
102491    41.3466
102502    45.9748
102525    56.3229

Optimisation: n = 7, k = 142.779968, m =  27.292578, Cal Start Pos = 102487

Digit position selection:   1000 100 10
Cal_End_Pos list:  [29301L, 30201L, 30291L, 30301L, 30311L, 30401L, 31301L]
29301     72.459
30201     70.735
30291     46.410
30301     42.141
30311     37.650
30401      5.454
31301      4.923
Min / Max  :  4.923   72.459
Half height: 38.691

30291  46.410194
30301  42.141027
30306  39.761214
30311  37.650028

Optimisation: n = 4, k = 120.472270, m =  10.905600, Cal End Pos = 30302


Exposure Time:  640  ms
=================================

Digit position selection:   10000 1000 100 10
Cal_Start_Pos list:  [92487L, 101487L, 102387L, 102477L, 102487L, 102497L, 102587L, 103487L, 112487L]
92487      5.650
101487      5.787
102387      5.789
102477     36.343
102487     40.853
102497     45.142
Break
Min / Max  :  5.650   45.142
Half height: 25.396

102432    17.2781
102454    26.3519
102477    36.3431
102487    40.8532

Optimisation: n = 4, k = 113.758804, m =  30.234468, Cal Start Pos = 102462

Digit position selection:   1000 100 10
Cal_End_Pos list:  [29302L, 30202L, 30292L, 30302L, 30312L, 30402L, 31302L]
29302     73.865
30202     71.849
30292     47.167
30302     42.751
30312     38.297
30402      6.218
31302      5.653
Min / Max  :  5.653   73.865
Half height: 39.759

30292  47.166769
30302  42.751245
30307  40.609615
30312  38.296837

Optimisation: n = 4, k = 122.659417, m =  10.905908, Cal End Pos = 30303

[Jean-Francois]

Hello Robin and Christian,

I do first a sequence of test with my laptop and the cable connected to the USB3 connector.
It was all working good with my new script. (Note, I install the last version of SC 3.2)

After that I stop SC and unplug the cable. And I restart with the cable connected to the USB2 connector.
... and nothing was working well.

It was ~ 15 minutes necessary to find only 1 setting manually.

Parameters: MONO8, 1920x1200, Traffic = 0, 20 ms.
With USB 3: Start ~ 6270, End ~ 1504360
With USB 2: Start ~ 7675550, End ~ 9147650

Note: important not to trap in the case of the "third transition".
For the Start value ... a lower value shall switch-off the LED and a larger value shall switch-on the LED
And the final GPS timing has to be near the wanted time of exposure.

Also not really comparable.
I guess that the variation with the USB 2 will be much larger as the USB 3.
On my laptop I have no problem to have 120 images/s with USB traffic = 0.

Robin, I guess that you will have a lot of problems, if you stay in "USB 2" mode.

In my script (precedent message), you can find the mathematical calculation coming from my analysis.
You can compare my results with your calculation.

Here some results in Excel table:

LED_calibration_with_script_new.xlsx

(319.87 KiB) Downloaded 92 times

Regards,
Jean-Francois

[Jean-Francois]

Hello Robin,

From your last message ... "it worked nicely, finding accurate values near to my original values of start=103000, end=31000."

????

The end position shall be larger than the start position ... it is the difference * 75000 or not ?
Also with your start 103000 and end 31000, it is something not OK.

Do you use USB 2 (or 3) ?

Note, with my laptop and USB 2, I do the search only manually, not with my script.


Regards,
Jean-Francois

[procyon12]

Hi, Robin,

Glad to see you again Jean-Francois.

Because of limited time, in the moment I could make only a few tests regarding Robin's initial post. So far I didn't involve your posts, Jean-Francois.

W7-64 i7 16GB, SC 3.2.6441 pro, USB2 Port, FW upgraded cam:

Mono 8; 1920x1200; USB trfc 0; bin 1x1; 640ms; immediately locked with default StP 6301, EndP 48004297
Mono 8; 1920x1200; USB trfc 0; bin 1x1; 320ms; immediately locked with default StP 6301, EndP 24004297
Mono 8; 1920x1200; USB trfc 0; bin 1x1; 160ms; immediately locked with default StP 6301, EndP 12004297
Mono 8; 1920x1200; USB trfc 0; bin 1x1; 80ms; immediately locked with default StP 6301, EndP 6004297 USB2 limit, only ~8fps

Does this help?

Cheers, Christian

[Jean-Francois]

Hello Christian and Robin,

I repeat some test with the USB 2 port on my laptop this afternoon.

Christian ... I think that to look only on the GPS "locked" is not sufficient.
If you want to use the LED calibration, then it should be stable and the StartPos shall find the real start and the EndPos the real end.
With your values ... try the simplest thing ... change the StartPos value by +/- 100 ... the LED should switch-off with -100 and should be on with +100.

With my laptop (W10 with last update, SC 3.2.6448 pro and camera firmware upgraded):
All tests with MONO8, 1920x1200, USB 2.0 port, USB traffic = 0 and bin 1x1

Third Transition:
640 ms : StartPos = 30370
320 ms : StartPos = 30370
160 ms : StartPos = 30370
80 ms : StartPos = 30370
40 ms : StartPos = 30370
20 ms : StartPos = 30370

Real Settings:
640 ms : StartPos = 102540, EndPos = 48067390
320 ms : StartPos = 102540, EndPos = 24066640
160 ms : StartPos = 102540, EndPos = 12069930
80 ms : StartPos = 3171300, EndPos = 9147650
40 ms : StartPos = 6174140, EndPos = 9147650
20 ms : StartPos = 7675560, EndPos = 9147650

Then I think the following ... the USB traffic slow down the transfer ... or add some waiting time before doing something ...

So, could be possible that with my USB 3.0 port and USB traffic, SC will find the correct starting values ?
The answer is yes ... at least for my computer and the USB 2.0 port.

I found that with USB 3.0 and traffic = 86, I can "simulate" the USB 2.0 and traffic = 0.

640 ms : StartPos = 102600, EndPos = 48071650
320 ms : StartPos = 102600, EndPos = 24072460
160 ms : StartPos = 102600, EndPos = 12069200
80 ms : StartPos = 3180360, EndPos = 9152650
40 ms : StartPos = 6177510, EndPos = 9152650
20 ms : StartPos = 7679750, EndPos = 9152650

I note that the EndPos is more "stable", but the StartPos depends strongly from the USB traffic value.
Means, for my computer I can simulate the USB 2.0 (traffic = 0) with the USB 3.0 ... by setting the traffic = 86.
It could be that for different computer, the traffic value will be different.

I can not test on a different computer. My desktop has only USB 3.0 (+ 3.1) and a second laptop has only USB 2.0.

Robin ... is it possible that SC detects the used USB port (2 or 3) ? and then changes the starting values depending on the connection.
For the USB 3 ... SC calculates correctly the starting values on different computer.
It could be possible, that the behavior of the USB 2 is stable between different computer.

Regards,
Jean-Francois

[admin]

Hi folks,

I agree with Jean-François - to be sure of a good calibration you have to make sure that a small change to the start/end point values gives you a difference between LED visible and LED not visible. Additionally, I will always check to make sure that the exposure time shown in the GPS window is roughly correct compared to the set exposure – for instance if I've set 160ms, then I expect to see an exposure time of roughly 160,000 microseconds. Just being 'locked' unfortunately doesn't tell you anything about the calibration, just that a good GPS signal is being received.

I don't quite understand what you by 'third transition' in your measurements – it seems to match with the sort of value I've been seeing for USB2 settings though. Could you explain what that means?

I have a USB board for the camera on its way to me – hopefully that will cure my USB3 problem and let me do some more testing.

Cheers, Robin

[Jean-Francois]

Hello Robin,

Look at this message from Kai getrost: viewtopic.php?t=2241&start=60#p15623
or go directly to the link: http://www.occultations.org/meetings/NA ... trost.pptx

You can read the page 50 to 57 ... Kai explains very detailed the LED ON at StartPos = 0.
(Note: do not use the presentation mode ... but enlarge the "note" lower section in PowerPoint for reading the detailed information from Kai)

Regards,
Jean-Francois

[procyon12]

Hello,

At least from the view of occultation observers this will be/is sufficient viewtopic.php?f=28&t=3135#p16338 :

For occultation work the users normally have working previously created profiles. Working means in this sense (I think you should also work with GPS on): From the GPS status window you have a GPS lock, the exposure time is near the chosen one, the sys clock does not differ very much wrt the GPS time. Then you may have a look at the framerate at the bottom of the SC GUI and to be absolutely safe you record a short video and look for dropped frames (maybe with PyMovie/PyOTE and or Tangra).
Mostly you change near the predicted occultation time the exposure time only. And normally then the "autocalibration" works well. In some cases you are said "BadCalibrationData - Reduce EndPos". Then usually a very little correction of the EndPos will be sufficient.

Only in the above sense the calibration is interesting for the observation of occultations. Bear in mind that the Swiss DVTI-camera (same sensor) doesn't need any calibration. There can be other reasons for QHY implementing the calibration.

My above short USB2 tests fulfilled all of these points ...

Knowing that SC is the only appropriate software to control the cam, it will be always good if we could improve things. And yes, there are not only occultation observers ...

Cheers, Christian

[Filipe Dias]

Hello,
I am new to all this, but I have been testing recently-bought QHY174 GPS and my understanding of it is still less than 48h however, I think I am getting it...
"GPS_ALT" is provided, so the new firmware is in there, I presume (yey!). SharpCap is v3.2.6442 (Pro)
This particular camera has not yet been connected to any GPS antenna since I took it out of the box, and also not for all this procedure.

I have been testing the numbers manually, by clicking the small buttons above and below the numbers in SharpCap.
I came to the conclusion that for finding a value, the behavior is the same if I use the "Start Pos adjustment" or the "End Pos adjustment", so to make it simple, I use only one for finding the values, instead of playing with the two controls. I noticed the following:

Any value below 46280 will show the LED on, regardless of exposure times (among the values I tested 50~250 ms).
The length of the LED blink is around "38 units"

I define (like in eclipses) 1st, 2nd, 3rd, 4th contacts as the moments where the condition "LED is lit" touches the condition "exposure underway".
(so 1st contact is the number immediately below when the "live stack" and histogram stretched image shows a tiny bit of the LED light;
2nd contact is the number for the first time that the LED illumination looks exactly the same (no live stack this time);
and so on..)

Values between:
0 to 46280 : LED on
around 46280 : LED dimming
46280 to 1st contact : LED off (out of exposure, before)
1st to 2nd : LED brightening
2nd to 3rd : LED on (during exposure time)
3rd to 4th : LED dimming
4th onward : LED off (out of exposure, after)

Code: Select all

Expos(ms)	1st		2nd		3rd		4th
 50   	10403595	10403645	14108655	14108705
 60   	 9646768	 9646804	14108664	14108700
 70   	 8901230	 8901270	14108660	14108700
 75   	 8528460	 8528500	14108660	14108705
 80   	 8144399	 8144437	14108663	14108700
 79.9 	 8155694	 8155732	14108663	14108700
 79.95	 8155693	 8155732	14108663	14108701
 95  	 7026093	 7026130	14108663	14108701
100  	 6653325	 6653365	14108663	14108701
150  	 2903054	 2903093	14108663	14108701
175   					14108663
180   					14108663
185   					14108663
186  	  203310	  203348	14108663	14108701
186.2	  180718
186.4	  169422
186.5	  158126	  158164	14108663	14108701
186.9	  158126	  158164	14119960	14119997
186.91	  158126	  158164	14119960	14119997
186.92	  158126	  158164	14131256	14131294
186.93	  158126	  158164	14131256	14131294
186.94	  158126	  158164	14131256	14131294
186.95	  158126	  158164	14131256	14131294
186.99					14131260
187					14131260
188					14210330
190					14357180
200					15102710
250  	  158126	  158164	18852984	18853022

Exposures shorter than roughly 186.5 ms seem to end at a fixed number..
Exposures longer than roughly 186.5 ms seem to start at a fixed number..
1 unit of time is between 1s/74.3E+6 and 1s/74.7E+6
If someone finds the exposure length is accurate to better than ~0.25 ms, this could mean they could be adjusting the clock frequency between 74.3 and 74.7 MHz to fine tune exposure duration! Does this make sense?
SharpCap rounds the exposure time we write, but before rounding it, it sends the unrounded number to the camera! If you write 79.9 or 79.95 you get the same calibration numbers, meaning the camera received these numbers, but SharpCap rounds the 79.95 to display 80.0; if you had written 80.0 as the exposure time you would get a correspondingly different calibration result!

Cheers,
Fil

[admin]

Hi,

thanks everyone for their contribution here – I'm going to have to spend some time digesting these and comparing them with the experience that I am observing at the moment.

Cheers, Robin