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Banding in dark frames

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#1 Gianluca67

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Posted 25 November 2012 - 09:36 AM

I wonder why I am getting banding in dark frames taken with my old SXVF H9. The banding is always present regardless of the temperature and the pettern are similar thuogh not identical from night to night. I attach 1 master dark taken at outdoor temp of 13C and the corresponding bias and another master dark taken at 18-21C.
Thank you for your help

Gianluca

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#2 Gianluca67

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Posted 25 November 2012 - 09:37 AM

bias

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#3 Gianluca67

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Posted 25 November 2012 - 09:37 AM

and the other master dark

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#4 microstar

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Posted 25 November 2012 - 12:51 PM

Does your SXVF not have cooling, because those seem like pretty high temperatures for darks? I know I see artifacts when I start taking pictures before my camera has cooled down.
...Keith

#5 Gianluca67

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Posted 25 November 2012 - 03:20 PM

THe SXVF has not cooling control. However the darks were taken with the CCD fully cooled (i.e. CCD powered and outdoor for 1 hour). The resulting chip temperature should be -30C from ambient. Any idea of the banding effect?

#6 Jeff J.

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Posted 25 November 2012 - 06:08 PM

Gianluca, I had an H9C for 6 years and I never saw this effect in any of my darks/master darks. I just checked my archives to be certain, and had 5min and 10min darks at 70F ambient with no bands. Since your banding changes from night to night, I wonder if it has something to do with the Peltier cooler (guess)? May want to contact Terry at SX for his take.

#7 David Rosenthal

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Posted 25 November 2012 - 06:40 PM

I saw something similar in a camera I once had and it turned out to be a bad USB cable. Try that first.

#8 microstar

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Posted 25 November 2012 - 11:52 PM

I saw something similar in a camera I once had and it turned out to be a bad USB cable. Try that first.


Good suggestion. Also, how clean is your power supply?
...Keith

#9 gezak22

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Posted 26 November 2012 - 01:16 AM

I saw something similar in a camera I once had and it turned out to be a bad USB cable. Try that first.


I once had diagonal banding. It must have been some kind of cross talk, as separating the power cord from the USB cord resolved the issue.

#10 Gianluca67

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Posted 30 November 2012 - 11:54 AM

Thank you for all the replies. I have tried to power the H9 with both AC and DC with the same result. I asked Terry Platt at Starlight and according to him it could be an effect of downloading. Perhaps it is the A-D converter ‘jumping’ between bit levels during download (it may not be perfectly monotonic), but that is a design or manufacturing issue with the hardware and not accessible to firmware fixes. Is there any test I can try before returning the CCD to Starlight? Shall I get another USB cable to see if the situation improves? The curious thing is that in the past I never got this effect. I have had to perform several firmware updates quite recently but I don't know if it is linked to those (Terry thinks no, however).
Thank you

Gianluca

#11 groz

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Posted 02 December 2012 - 10:47 AM

That looks to me like a problem with data transfer, likely coming from the usb side of the system. Is it going thru a usb hub ? Do you have another usb cable to try ?

If you are running thru a hub, the FIRST thing to do, is connect directly to a computer, and bypass the hub.

I've never seen that with either of our cameras, both the older SXV-H9. We use them in a rather 'extreme' usb environment so to speak. Between the computer and the hub, we have 2 active usb extension cables to run out to the back deck, then a 7 port powered usb hub at the telescope, with all the requisite gadgets plugged into that. I did replace a few of the usb cables over time, for cables with a better build quality. The ones that came with our SX gear (two cameras, one filter wheel) were good, but, some of the others were suspect.






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