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Does this dark frame look normal to you?

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#1 jbalsam

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Posted 10 January 2013 - 10:06 PM

Hey folks. Check out this stretched crop of a 5min dark frame I just took with a camera I just bought used (atik 383l+ mono)
Posted Image
I've never seen streaked warm/hot pixels like this before in any type of camera. I've used a meade dsi pro 3, a starlight xpress m7 and m8C, a qhy5, and a canon dslr, and never seen anything that looked like this. I don't imagine it will be a problem, but I am curious if other people with this camera or with other 8300 sensor cameras see this.

#2 shams42

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Posted 10 January 2013 - 10:18 PM

I think something is wrong. Dark frames with my 8300 chip don't look anything like that.

#3 rigel123

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Posted 11 January 2013 - 12:16 AM

Definitely does not look normal

#4 zerro1

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Posted 11 January 2013 - 03:12 AM

My QHY9 8300 never displayed anything like that. First it looks hot, then it almost looks like the hot pixels are blooming...

#5 alpal

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Posted 11 January 2013 - 03:49 AM

It must be a faulty sensor.
Is it under warranty?

#6 orion69

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Posted 11 January 2013 - 04:15 AM

What power supply are you using?

#7 wasyoungonce

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Posted 11 January 2013 - 04:32 AM

What cap did you have on the camera? Lots of energy like IR can pass thru plastic caps and be detected by the sensor as light energy.

Also ..is it cooling?

#8 flolic

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Posted 11 January 2013 - 04:46 AM

I have seen exact behavior while building and adjusting my homemade KAI4021 camera. But I just can't remember what caused it :(
I think it was related with bias voltages applied to CCD, and possibly bias/offset/gain settings of AD converter. And I am quite sure it was temperature dependent, so check your cooling first ;)

#9 siovene

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Posted 11 January 2013 - 04:53 AM

Are your USB and power cable running together? Try to separate them.

#10 MikeCatfin

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Posted 11 January 2013 - 08:26 AM

I have an Atik 383L+ and my darks look nothing like that. Check the cooling and voltage.

#11 jbalsam

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Posted 11 January 2013 - 01:35 PM

A service rep from Atik suggested using a different power supply. I measured mine, and it was in fact putting out only 11.95V (slightly less than the required 12). I connected the camera to a regulated variable DC power supply, and set it to 12.5V and then 13.2V (the Atik guy said don't go above 13.8V) The problem never entirely vanishes, but it gets much better. See below. Posted Image

higher res image here, to see details: http://cdn.astrobin....4d9350c1170.jpg


Thanks for all the responses. Yes my cooling was on (set to -10C), and the shutter was closed, a plastic cap was on, and the camera was turned face down resting on a black lab bench.

#12 David Rosenthal

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Posted 11 January 2013 - 02:19 PM

Try placing a layer of aluminum foil under the plastic cap. It will stop cosmic rays from showing up. Perhaps there is some similar anomaly making its way onto your sensor. Cant hurt!!!

#13 jbalsam

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Posted 11 January 2013 - 02:33 PM

As far as I know, all aluminum foil stops is infrared. I think you need a few meters of lead or granite to stop cosmic rays.

Either way, I tried it, no difference.

#14 shams42

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Posted 12 January 2013 - 12:10 AM

Looks like you should crank it up to about 15 volts. :)

Unfortunately, though, I think there is a problem either with the sensor or with the electronics.

Have you had a chance to shoot any light frames with the camera yet?

#15 jbalsam

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Posted 12 January 2013 - 09:37 AM

Haha... yeah, sounds good. My next question will be "is this smoke pouring out of this camera a normal operational function?"

I haven't shot any light frames yet (it's been cloudy since I got the camera, as is expected). I pretty sure it's an electronics issue too. What I am concerned about is that stars will act the same way as hot pixels and streak to the side by a few pixels.

#16 niteman1946

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Posted 12 January 2013 - 01:51 PM

Hi J,

I've got the same camera and am using the Atik recommended power converter. No problems so far.

I see you posted on the Atik forum. Have you contacted their tech support directly? I've found them to be fairly responsive and knowledgeable.

Good luck,

Mark

#17 jbalsam

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Posted 13 January 2013 - 09:47 AM

Hey Mark -

Yeah I contacted them directly and they responded within about 12 hours, which was great. They suggested trying the higher voltage. I emailed them back with these results, showing the the problem is improved but not eliminated. Waiting for Monday for their next response. I figured I'd post in both places to get as much expertise from the community as I could!

What is the rated output on the power converter that you have, Mark?

#18 jbalsam

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Posted 23 January 2013 - 05:49 PM

Hey folks -

Thanks for everyone's input. Finally worked out a solution, and (shocking) it actually turned out to be the first thing anyone said to me: the power supply.

I said above that I tried higher voltages (up to 13.2V), and it didn't solve the problem entirely. Well, it turns out I forgot 100% of what I ever learned about circuits and voltage drops. I was measuring the voltage at the plug before I plugged it into the camera, not WHILE it was plugged into the camera. So, I measured the full 13.2V that the supply was putting out. I didn't of course realize that the alligator clips I was using to connect the power supply to the camera were causing a 1V drop in voltage when there was current flowing. So, I feel pretty silly. A lot of messing around measuring dark and bias frames and trying to calibrate out this noise issue and talking to tech support and contemplating sending the camera to Europe for repairs, and it would all have been solved if I'd remembered some high school level electronics knowledge.

All's well that ends well. I guess I can go re-image everything I've done in the past two weeks now =)






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