QHY 174 GPS Calibration LED issue // USB Traffic weirdness

TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Tue Jan 21, 2020 10:45 pm

Hi Niko,
Thanks for this useful information: You wrote earlier...

" Tim - what DCF 77 receiver do you use? 'Normal' DCF receivers cannot deliver a precise signal: The necessarily very narrow bandwidth of the receiver causes a sometimes considerable delay of the output pulse. (We have 77.5kHz...) This is also dependent on the field intensity of the DCF signal. (Just turn the antenna by 45° and repeat the measurement.)
I held a short talk at the ESOP in Berlin 1996 about 'Accuracy limits of DCF-77 receiver modules'. In Berlin I measured a delay of 50..60ms of the receiver's ouput to the direct 77.5kHz-Signal (at this time the most accurate time source available)"

I appear to have made in independent confirmation of this "DCF77.5 inaccuracy" by videoing the pulse with GPS time overlay. I therefore withdraw by comment on QHY being delayed by 20-30ms based on this unreliable method. It is a commercial DCF unit (15 Euro) similar in appearance to those made by Reichelt Electronik.

Tim

TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Wed Jan 22, 2020 12:40 pm

Dear All,
I find these controls rather non-intuitive. What figures should i be comparing in the screen shots? Please could someone provide a guide to the whole calibration process with annotated diagrams. I would like to understand what is being discussed, and to do the calibration myself. Hopefully i may then be able to contribute. Thanks very much in advance. At the moment I feel the knowledge gap between newbie and expert is widening - I'm still a newbie!

cheers - Tim

procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Thu Jan 23, 2020 1:49 am

Hi Tim and all,

because the LED calibration depends on many settings, I've made a test with a dedicated set as I usually apply for occultation work, see attachment testset_02 (QHY174M).ini.
This you can paste to: C:\Documents and Settings\Administrator\AppData\Roaming\SharpCap\CaptureProfiles\ ...

Then you should completely cover the camera and with usb3, GPS signal receiving antenna > "locked state", (powering 12V DC not required), and after loading this ini file, you should see a black frame with possibly (not required at this point) lighting from the LED at the frame's right side (not yet calibrated, a starting point only).

You now have a basic setup for testing the calibration according to the SC help. You may not capture frames, but you can (snapshots > fits - header include a lot of data and gotten camera settings tell you, what you done); also you can save found calibration settings for further work as capture profiles (for this, switch the LED off !).

In my test (SC pro 3.2.6212.0 32bit; w7-64bit home premium, Intel i7 2.2GHz, 16GB RAM, SSD) I checked the dependence of the 2 calibration values (each the sum of "coarse" and "fine") from the exposure time for usb-traffic = 5 and 0. You have to vary only the exposure times for the two usb-traffic values 5 and 0 and find out the respective calibration values start and end position, like described in the help.
As can be seen, the start position is constant while the end position grows linearly (and does not differ in terms of usb traffic).
It would be interesting if someone could confirm these measurements.

Some hints @ Robin:

> above 120 ms exp. time calibration of end pos. not possible (?); below 20 ms calibration difficult

> according to https://www.qhyccd.com/index.php?m=cont ... =30&id=190 , also the cal. end pos shall be constant (?), however, I think they refer to their own software EzTimeStamp (?).

> the frequency stabilisation works well

Christian
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TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Thu Jan 23, 2020 12:05 pm

Hi Procyon12/All, I can confirm that the LED end calibration increases as the USB traffic increases using the little scroll bars. The start point is unchanged (zero on my camera). Here are my readings: (16bit, 1x1, 640x480)

USBtraffic/Start/End: 0/0/4500, 3/0/5500, 5/0/6000, 10/0/7500 (SC 3.1.5143)

I also installed 3.2.6212, with similar trend, BUT the GPS time update is broken. The system time is shown, but the GPS time is static at some value and doesnt change. Can anyone else confirm this ? (W7, i3, 4Gb RAM, Hybrid drive). Its fine with the earlier version of SC.
( Ive not yet used 3.2.6185, so no comparison with this)

Tim

procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Thu Jan 23, 2020 1:18 pm

Hi Tim,
Maybe you have a mismatch. My posting with all data and especially the INI file only refers to SC 3.2.6212.0.
This version should also work for you if you have a fresh installation. Please deactivate SC's "Restore camera settings automatically" - Settings / General. If you start SC now, the default settings will be loaded and the camera must run. Then load my INI file and everything should work including GPS. My test shows the dependence of the start/end position on the exposure time with the parameter usb traffic (5 and 0).

Christian

TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Thu Jan 23, 2020 3:56 pm

Hi Christian,
Thanks for the tip - it worked. Is an INI file a Capture profile?

The problem was caused by the default Capture profile being loaded, one that i set up in the earlier SC version. When the default profile option (under Manage) is de-selected, then yes the settings are rolled back totally, and the GPS now works. I did deactivate SC's "Restore camera settings automatically" but this was not enough to fix the problem, at least that was the impression.

Does this mean I should delete and re-create the capture profiles for the new version? - Simple enough now that i'm up-to-speed.

I have read your notes on USB traffic - nice work, and i will incorporate this into my capture profiles.

Cheers - Tim

procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Thu Jan 23, 2020 4:33 pm

Hi Tim,

Glad to hear this :-)
Yes, the SC-called "capture profiles" are INI (txt) files, located at C:\Documents and Settings\Administrator\AppData\Roaming\SharpCap\CaptureProfiles\ ... If you know what you do, you can edit them with an editor (make backup copies).
Since the special version 3.2.6212.0 has some new features (e.g. frequency stabilisation and new calibration sliders) there can be problems with old profiles. But as I wrote, you can adapt the old ones to the new.

You wrote: "i will incorporate this into my capture profiles"
These are preliminary results and need to be proved by others and also checked by Robin.

Christian

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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin » Sat Jan 25, 2020 7:57 pm

Hi Christian

Thanks for your detailed discussion of the different values needed for calibration with different settings. It looks like I may need to extend the calibration range to allow for longer exposure calibration in a future version. I was also wondering whether I need to make the adjustment easier perhaps by having three sliders find/medium/coarse rather than the current two.

Another piece of information that would be useful if you have it to hand is how sensitive the recorded exposure time is to the exact value of the calibration parameters. By this I mean that if we want the exposure time to be correct within 1 µs, how close does our calibration value need to be? +/-10 ? +/-50? +/- 500? If for instance I knew that we didn't need to be closer than +/-100 then it would help me work out the best way to set up the sliders to give good control and accuracy.

Cheers, Robin

procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Sun Jan 26, 2020 3:34 pm

Hi Robin,
thanks for your work.
In the meanwhile I have a more precise diagramm. I (there are no other results known for me) found - and only with my system and within the reported ranges:
The ExpStartPos depends only on the USB traffic (linear).
The ExpEndPos is depending on the exp. time (linear).
I tested only for 16bit, with 8bit there are other results. It seems that gain, offset, area, binning have no influence.
admin wrote:
Sat Jan 25, 2020 7:57 pm
It looks like I may need to extend the calibration range to allow for longer exposure calibration in a future version.
I agree. But there is a question for me, because QHY wrote that the Cal EndPos will not increase with the exp. time (?):
https://www.qhyccd.com/index.php?m=cont ... =30&id=190
admin wrote:
Sat Jan 25, 2020 7:57 pm
I need to make the adjustment easier perhaps by having three sliders find/medium/coarse rather than the current two.
Maybe. The calibration in the current state is bit tricky..., 6 sliders could be too much, however? Moving with the keyboard arrow keys might help.
admin wrote:
Sat Jan 25, 2020 7:57 pm
Another piece of information that would be useful if you have it to hand is how sensitive the recorded exposure time is to the exact value of the calibration parameters. By this I mean that if we want the exposure time to be correct within 1 µs, how close does our calibration value need to be? +/-10 ? +/-50? +/- 500? If for instance I knew that we didn't need to be closer than +/-100 then it would help me work out the best way to set up the sliders to give good control and accuracy.
For me, there are some open points.
How or where can I see the result of the succesful calibration (apart from the LED)?
I observed that in the case of an exact calibration the exp. time shown in the GPS status window is not exact in the range of about +/- 100 µs. To get it exact I must move the calibration slider(s) - but this is destroying the calibration found.

Example in calibrated state (ini):
Enable Live Broadcast=Off
USB Traffic=3
Offset=0
Amp Noise Reduction=Off
Frame Rate Limit=Maximum
Gain=480
Exposure=100
Calibration End Pos (Fine)=9361
Calibration End Pos (Coarse)=7500000
Calibration Start Pos (Fine)=14140
Calibration Start Pos (Coarse)=0
GPS Calibration LED=Off
GPS Freq Stabilization=On
GPS=On
Timestamp Frames=On
Contrast=0
Brightness=0
Gamma=1
Temperature=27.9
Target Temperature=0
Cooler Power=255(Auto)
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1


The chosen exp. time is 100 ms, in the above calibrated state the GPS status window shows an exp. time 99.936 ms. The counter was precise to about +/- 6 µs, with frequ. stab. on. If I decrease the the CalStartPos from 14140 to 9361 the exp. time in the GPS status window is now 99.999 ms but the calibration is lost (?).
In both cases the measured exp. time of a recorded SER was 100.12 ms / 9.987 fps, no dropped frames.
This could give you also a feeling about the accuracy.

Christian
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin » Sun Jan 26, 2020 5:44 pm

Hi,

Thanks for the update – I think I would be inclined to believe the GPS info regarding the precise exposure length after calibration rather than expecting the exposure length to precisely match the value that is set using the exposure slider. The camera sensor was never designed as a scientific sensor, so expecting exposure to be accurate to better than 0.1% may well be beyond the design criteria of the sensor.


I must test my camera to see if the calibration values are essentially the same as the ones you observe – if that's the case I may be able to automate adjusting the coarse value of the parameters based on the USB speed and exposures and then offer the user a fine adjustment control for any necessary tweaks.

Cheers, Robin

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