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ZWO 1600 Mono Pro, Bright spot on darks

astrophotography
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#1 Erik G

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Posted 21 February 2019 - 02:39 AM

Hi,

I have done some dark testing on my new ZWO 1600 Pro Mono camera. The attached dark is 300sec. Gain 300 Offset 50. The camera is not attached to the telescope it is covered by cap, two different caps have been tested, it is located in a dark room, and aluminium foil at the front to be sure that no stray lights reached the sensor. At the lower left part of the dark there is a bright sport with a surrounding halo, the spot is located at the same place for different caps. . The bright spot increases in intensity with lower temperature, and of course exposure length. The same pattern is visible at "high" temperature short exposures but with lower intensity. 

 

I am 100% sure that no stray lights reached the sensor. For me it looks that there is either a large number of hot pixels or another defect on the sensor that create the light and that the halo is the reflection from that light being reflected by the sensor glass.

 

Any that can help me confirm or come with another explanation? 

 

I have not tested this in a full imaging sequence so because I assume that the "defect" be removed by calibration, it will possible add and "artifact". 

 

Her is the full frame autostretced in Pixinsight :

 

 K0bctDPDgkCU_1824x0_wmhqkGbg.jpg

 

 

The bright spot:

 

xexBoyaPWCs9_1824x0_wmhqkGbg.png

 

Erik G



#2 Dynan

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Posted 21 February 2019 - 02:48 AM

Certainly looks like a defective sensor. A hot pixel here and there (with all light well eliminated as you have) can be tolerated. But you have a globular cluster's worth in one spot. I'd have the seller exchange it. How long have you had the camera?



#3 Erik G

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Posted 21 February 2019 - 02:53 AM

Thank's Dynan

 

Just got it, it was the first test I did to verify the quality of the sensor. I have problem with convincing ZWO that it is a defective sensor. They what me to take lights++ but I have no interest in spending more time on the camera than I have so it is good that have some others opinion :)

 

Erik



#4 entilza

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Posted 21 February 2019 - 06:06 AM

Yeah that's odd. There is a circle pattern as well.

How does it look at a lower gain? Just curious.

I wonder if you physically look at the sensor if you see any markings on it.

Good luck with this.

#5 Erik G

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Posted 21 February 2019 - 07:23 AM

The difference related to gain is there but the difference related to cooling temperature is bigger.  

 

ZWO has accepted to replace the camera and they will since this is the second "defect" I have got take the return cost. I live in Norway, there are approx. 4-6 weeks left of the season so I hope I can test it before it is to late.



#6 DSO_Viewer

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Posted 21 February 2019 - 12:18 PM

The difference related to gain is there but the difference related to cooling temperature is bigger.  

 

ZWO has accepted to replace the camera and they will since this is the second "defect" I have got take the return cost. I live in Norway, there are approx. 4-6 weeks left of the season so I hope I can test it before it is to late.

Glad to see that they will replace it. Even if you get it after the 4-6 season you can always test it anytime using darks.

 

Steve



#7 twidget

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Posted 21 February 2019 - 06:17 PM

Separate issue from the bad spot......the amp glow in the top-right and bottom-right corners seems to be excessive, also.  I have that camera, and I just looked at some 300s, 300g, 0C and -20C darks I made with the camera capped and in a towel-covered cooler a few months back, and the amp glow is there, brighter in the 0C darks, of course, but MUCH less than that in your dark. With that level of amp-glow and the spot, I'd say you are absolutely right to get the camera replaced.

 

Good Luck with the replacement!  BTW, I think the 1600 is a good camera.

 

Mike 



#8 Erik G

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Posted 22 February 2019 - 12:21 AM

Thank's to Steve and Mike. 

 

I am sure that its a good camera so just waiting for one with the "right" quality.

 

Erik


Edited by Erik G, 22 February 2019 - 12:21 AM.


#9 Lead_Weight

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Posted 22 February 2019 - 01:00 PM

You might see if they would allow you to buy a new one, and then refund your money when they get the defective unit. This would keep you from having to await the round trip of sending back your unit, then waiting for a new one.


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#10 cfosterstars

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Posted 22 February 2019 - 02:52 PM

Separate issue from the bad spot......the amp glow in the top-right and bottom-right corners seems to be excessive, also.  I have that camera, and I just looked at some 300s, 300g, 0C and -20C darks I made with the camera capped and in a towel-covered cooler a few months back, and the amp glow is there, brighter in the 0C darks, of course, but MUCH less than that in your dark. With that level of amp-glow and the spot, I'd say you are absolutely right to get the camera replaced.

 

Good Luck with the replacement!  BTW, I think the 1600 is a good camera.

 

Mike 

That amount of amp glow is typically of the ASI1600MM cameras that I have. I have two of them and both show the same. This is no issue at all. If you use dark frames that are unscalled and at the exact exposure, gain, offset and temperature of the light frames, ALL the amp glow calibrates out of your light frames. That is a MUCH higher gain than I use. The highest gain I have ever used is 200 for narrow band filters at F/5.5. I will be trying a gain of 225 for narrowband on my SCT at F/8.5 but I am not sure that I will need it. However, that bright spot is nasty and the camera needs to be replaced. I really like my 6 ZWO cameras by the way. I have had no issues really.



#11 Erik G

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Posted 22 February 2019 - 03:28 PM

Good proposal Andrew, the only problem with that could be 25% tax, not much if a low value from ZWO smile.gif

 

According to amp glow both camera that I have tested have had approx the same. No problem with proper calibration. 

 

I have only tested HA with the first sample where I used 300/50 with for me ok result, will try other settings when the new "perfect" arrives. 

 

Link to the HA image https://www.astrobin...6475/F/?nc=user

 

Erik 


Edited by Erik G, 23 February 2019 - 01:28 AM.



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