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SBIG St8300 unusually high blooming spikes

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#1 Guillermo

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Posted 09 April 2020 - 10:24 AM

Greetings,

 

My 2008 ST8300M camera has been stored for quite a while now and I remember it was working perfectly fine back then. Now, I have been using it again for these quarantine weeks and came up with a few issues. Among those, my images have been showing these vertical spikes (please have a look at attached sample subframe). It seems to appear on every bright star as a vertical line towards the bottom of the image (no spikes on the upper projection of the star) and on every single frame.

I was wondering if the sensor is simply coming to the end of its life (in which case it would be quite frustrating, given it has been barely used and stored for years) or there may be something else, such as some setting in the latest drivers that is causing this problem (e.g., gain correction or ABG that need activation). Any help is appreciated. 

 

Cheers

 

Guy

Attached Thumbnails

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Edited by Guillermo, 09 April 2020 - 10:36 AM.


#2 StephenW

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Posted 09 April 2020 - 11:17 AM

That is weird - almost looks like ABG is turned off and/or failing.

 

Have you used the SBIG Driver util app to make sure both your drivers and the camera firmware are at the latest versions?  (you need to go to the second tab in the app to check your camera firmware version)



#3 WadeH237

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Posted 09 April 2020 - 11:49 AM

To me, those don't look like blooms.  They look like readout trails.

 

The difference is that blooms form during the time that the camera is exposing when pixels become saturated.  Readout trails happen after the exposure, when the camera is reading the data from the sensor.  I would start troubleshooting by looking at any driver settings that have to do with download speed, and make sure that you select the lowest speed.  I don't know for sure that changing the download speed will affect the CCD readout, or if it only affects how the USB is used, but it's worth a look.

 

My ST-10 had a number of hot pixels that would result in similar readout trails, but I never saw stars produce them.


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#4 Dan Crowson

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Posted 09 April 2020 - 02:11 PM

I think the KAF-8300 tends to bloom to the right or left, too.
 
Dan



#5 Moreflying

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Posted 09 April 2020 - 03:52 PM

The only time I've seen the Kaf 8300 bloom is when binned 2x2 and it doesn't look anything like that.



#6 Complexmystery

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Posted 09 April 2020 - 04:14 PM

I had this exact issue with my QHY9 and have seen it in the lab with an Andor ICCD. Both issues seemed to be related to the shutter. For the qhy, my shutter was getting stuck so I had the bright idea to make it stay up. I would get this "blooming" as the shutter was not there. While I really am unsure why the readout is not able to work properly without the shutter, I would make sure that the shutter is working as it should, and perhaps call SBIG and mention your issue to them. 

 

-Josh 


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#7 Guillermo

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Posted 09 April 2020 - 05:53 PM

That is weird - almost looks like ABG is turned off and/or failing.

 

Have you used the SBIG Driver util app to make sure both your drivers and the camera firmware are at the latest versions?  (you need to go to the second tab in the app to check your camera firmware version)

Yes, kind of weird. I did, driver and firmware are up to date



#8 Guillermo

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Posted 09 April 2020 - 06:09 PM

I had this exact issue with my QHY9 and have seen it in the lab with an Andor ICCD. Both issues seemed to be related to the shutter. For the qhy, my shutter was getting stuck so I had the bright idea to make it stay up. I would get this "blooming" as the shutter was not there. While I really am unsure why the readout is not able to work properly without the shutter, I would make sure that the shutter is working as it should, and perhaps call SBIG and mention your issue to them. 

 

-Josh 

Thanks Josh. Indeed, the mechanical shutter gets stuck apparently due to malfunctioning of the motor and it coincides with the appearance of this blooming just as you mentioned. I think you have pinpointed the cause. It is still puzzling to understand why the sensor has this behavior. If these are not blooms but readout trails, as someone mentioned earlier, it may somehow have to do with downloading and readout.


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#9 vakulenko_sergiy

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Posted 09 April 2020 - 06:35 PM

During CCD reading row are shifted, due to shutter malfunction bright stars are exposed to the shifting image and this lead to the trails. To reduce this effect you can increase readout speed, but this might bring another issue - higher readout noise.


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#10 Guillermo

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Posted 11 April 2020 - 04:17 PM

Hey everyone, I would like to provide a little update on this seemingly abnormal blooming on the KAF8300 sensor. First, I would like to thank you all for your comments because you have helped me narrow down the issue and very likely to the solution to it.
Yes, the mechanical shutter was getting stuck, so I decided to remove it and while doing so, I realized that there was a little metallic pin on my SBIG ST8300 that serves as a rail for the shutter. This pin was putting some friction on the shutter, so I decided to check what was going on the opposite side of the electronic board where the motor serving the shutter was located. When pulling off the shutter, that nice little Japanese motor was working as expected, so the friction was probably causing it not to freely move around or perhaps the motor was not getting enough amps to actually do its job. Then I checked the two allen bolts arrowed on the picture below, and confirmed they were loose, so the former problem was the most likely issue. So, I gently moved the fan towards the top of the image while giving the required torque to the bolts, which in turn allowed the pin (located on the opposite side of the electronic board) to   reduce the friction on the shutter. VoilĂ ! The shutter was now free to move around and the motor was activating and closing the shutter as expected. So, before the moon and the clouds arrived late during the night, I decided to repeat the session on IC2944  (I am located in the southern hemisphere in Chile, so this object is near the zenith at the beginning of the austral autumn night). Needless to say, the blooming effect was gone and you can see what the image now looks like after some minor postprocessing.
In conclusion, the KAF8300 does require the shutter to avoid readout trails from bright objects while reading on a row to row process. Secondly, sometimes there are easy to solve mechanical problems. In this case, you would want to make sure the shutter is free to move before going for an expensive motor replacement, so a bolt torque check on the cooling fan should be required from time to time. Hopefully, things should go back to normal now. I mean for the camera, not for us out there in quarantine.

Cheers,
Guy

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  • ic2944_100420_LRGB_mini.jpg

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#11 WadeH237

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Posted 11 April 2020 - 06:21 PM

Great followup!

 

I'm glad that you found the problem and it was an easy fix.



#12 Complexmystery

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Posted 17 April 2020 - 09:39 AM

Glad you managed to fix it and not have to send it in! 




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