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  #41  
Old 12-10-2011, 08:43 AM
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I was just joking folks. Why mess with something built by experts.

It seems to be that a good guiding principle is to go a low as practicable.

I have been following this thread with interest as I have yet to use a cooled CCD astro camera.

My frankenfridge for the Canon 5DH never had a problem with condensation as the camera and sensor were the hottest objects in the fridge.

Bert
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  #42  
Old 13-10-2011, 11:24 PM
ptc (Richard)
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Originally Posted by jase View Post
Thanks Richard. No apologies needed, in fact since you're in the region if you make it to Singapore over the next couple of days I'll buy you a beer or two, or more.

I would like to clarify that the CCD chamber seal discussion on cycled cooling was not only applicable to Apogee cameras as you indirectly imply, but ALL camera manufacturers. Your response was precisely what I wanted to hear regarding the CCD chamber seals. Thanks. No need for a warm up period either - great. I would be most interested in reading your supporting materials on random radiation damage be it permanent or temporary, along with the likelihood. Feel free to post the link here or private message me offline once you've got access to your library. Appreciate your input.
Hey I am happy to help if I can but I also have pretty strong positions I take, mainly because I've either been there and done that or I just happen to know the material from my many years as a semiconductor design engineer (35 years in the biz). But I will always give reasons why I say what I do rather than just say "because I say so" or "I heard that blah blah is true". My world is a world of truth and facts and not much grey (except patents, and that is an entirely different topic)...

On chamber seals: the reason I singled out Apogee is because Wayne Brown, the owner, has gone on the record stating that :
1) they take a half hour to cool down to prevent damaging the sensor, claiming that the 5-7 minute slew everyone else does constitutes a military "destructive test" which is just utter nonsense. Mil Standard 883C clearly states the temperature slews for thermal shock (destructive testing) take less than 10 seconds to go from -40C to +125C. Of course most people that read that poppycock from him would have no knowledge of Mil Standard 883C, but I do.
2) backed off on the damaged sensor claim when confronted with the facts that there is not a pile of damaged sensors accumulating from all vendors but Apogee and that certainly creates a mountain of evidence to refute his statement. So the position morphed into a chamber seal issue. Of course there's still no mountain of failed camera chamber seals piling up so that statement seems unsupportable by fact.

So the third possibility is the thermal runaway issue, which is where I'd lay my money were I a betting man. Seeing how the air cooled one has stagnating airflow in the heatsink and with four puny little fans, it looks to me like they can add heat to the sink faster than they can shed it.... that translates to thermal runaway in that situation.

The simple workaround is to limit the power going to the TEC to prevent that situation from arising. The U8300 I tested never showed the power level higher than 37% during the cool down when I tested it and if that percentage is honest, then that sure looks to me that they have intentionally limited the power being applied to the TEC.

The early STL11Ks had a propensity to have that thermal runaway problem under some conditions so it isn't like this is unprecendented. To SBIG's credit they fixed them including the ones that had been sold before they figured out that they had a problem.

In my opinion Apogee if my suspicion is true, is taking both a lazy and sleazy way out by making up a cock and bull story designed to deflect criticsm from the believers and at the same time cast a rock at their competitor by creating FUD that there's a long term reliability problem lurking in the bushes in all cameras that aren't made by Apogee.

Well it ain't so on the reliability problem as evidenced by tens of thousands of user-hours and no failed seals.... so where are they Wayne? Furthermore why is the same damn seal suddenly reliable when you pay $2000 extra for the D09 cooling option? I smell a rat, how about you?

It really chaps my tail end to see people on the supply side exploiting the trust and ignorance of their customers who largely not technical and simply believe what they are told. Unfortunately unless people speak up when they smell the wet, warm and brown being cast about, it will never stop. I do speak up and encourage others to as well. We all win when we are dealing with honest brokers rather than someone ready to pull a fast one on you. When people call them on the carpet when they are lying and it happens again and again, it will stop or they will lose their customers trust and eventually the customers too.

Regarding S'pore: I seldom get down there but there's a technical conference that is held there annually for which I may submit a paper next year. I missed the Call for Papers this year so I am not on the agenda.

However when I head that way I will certainly rattle your cage ahead of time as I would really enjoy meeting you and all the rest of the participants on this forum face to face sometime... I've met Gordon Haynes (UK) and Antonio Rosalino (PT) in my travels and nearly got to meet Kitajima-san (JP) this past spring but the Fukushima Daiichi disaster stopped me from going to Nara to present an accepted paper at the International Conference on Electronic Packaging held in April of this year. I just had to abort the trip out of big concerns for food/water safety.

Just to show you folks that I'm not feeding you a line about what I do I call your attention to this recent news release (this is why I am in Korea)

http://finance.yahoo.com/news/Invens....html?x=0&.v=1
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  #43  
Old 14-10-2011, 06:46 PM
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Originally Posted by ptc View Post
I'll second that.. chilled water must be used with great caution: otherwise the condensation resulting from it will indeed put the electronics at risk!
At risk perhaps,but I have often liquid cooled my st10xme with iced water till it was dripping weT in hi humidity without a problem at all.
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  #44  
Old 14-10-2011, 08:36 PM
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why you don't want to let your camera get wet

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At risk perhaps,but I have often liquid cooled my st10xme with iced water till it was dripping weT in hi humidity without a problem at all.
That is asking for trouble and here's why. When the PCB gets wet the solder on all those surface mount chips can get wet and if it does, it can and will cause dendrite growth. Those are little "whiskers" that grow like spikes from the solder. Eventually they end up shorting solder balls or traces together.....

http://www.narrowbandimaging.com/inc...-corrosion.jpg


The failure can happen rapidly in the presence of ionic contaminants or it can take some time but eventually that's the failure mode. so your camera may work OK now but eventually it will fail. I have seen three ST10XMEs that first had the -X guider output fail due to this dendrite growth. One was mine and it happened because I too had been using chilled water and my camera got soaking wet twice. Mine failed about 6 months later. Another happened to a fellow that lives on the Florida Gulf Coast and is in a very humid environment and dew condensed on the camera (he lives near salt water in a humid environment but he was not using water). He was advised by SBIG to open it up occasionally and use a toothbrush to scrub the PCB

Another failed for a fellow in Tennessee that was in a very humid scenario using chilled water

One thing that can be done is for the manufacturers to use conformal coatings on the PCBs once they are assembled. That is how marine electronics such as VHF radios and Radar systems are made robust.

I've been complaining that none of the makers do that. For the money we spend on this stuff, they could afford a few bucks to conformally coat the PCBs but no one does....

the Proline cameras have the electronics protected from the elements. That's a good thing. The Microline does not have environmentally protected electronics.

Obviously the ST10 does not either. Not sure about other brands

The use of fine pitch surface mount components and ball grid arrays only aggravates the problem. Unfortunately my industry has switched nearly exclusively to such packaging technology. People want tiny Iphones and notebook PCs so miniaturized components is the way it is done.

The area array BGAs (ball grid arrays) are particularly bad because all of the solder connections are below the chip's package and cannot be visually inspected.... you can use underfill to prevent moisture from getting in but that makes rework difficult

here's a nice reference that speaks to many other failure modes including what I just described

http://www.narrowbandimaging.com/inc...d-Only__01.pdf

look at page 7 for the moisture induced dendrites. Simply getting the PCB wet can cause growth but do so with power applied and you have it accelerated

At the end of the day you are better off buying a camera that is designed to cool well. SBIGs and QSIs do not have that property.
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  #45  
Old 14-10-2011, 09:42 PM
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Yes, I understand and agree with what you say. I am asking for trouble in the long term. Seems daft to me sbig don't conformal coat, it's not hard or expensive. I might even do it myself (after a scrubbing)
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  #46  
Old 20-10-2012, 09:14 PM
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Quote:
Originally Posted by mill View Post
I have a QHY9m and have it set to -20 all year round.
Even in summer it goes to -20 and runs at 60% power.
I am running it at 13.8Volt so i set it to not go higher than 75% power.
What was the result of this thread?

I have a QHY9 camera & I have run it quite a few times at -31 & once at -34 degrees.
I have been told that there is a risk of eventually cracking the KAF 8300 sensor.
Apparently the lowest you should go is -20 degrees & you should
go to that temperature slowly & also allow the chip
to warm up at the end of the imaging session - slowly.

Has anyone ever cracked their sensor chip by running it all the time at the coldest temperatures?
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  #47  
Old 20-10-2012, 11:18 PM
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QSI583, during winter it holds -20C easily. Spring the same. Summer most nights -15C, rarely -20C. Darks done every 3-4 months. The images start to show black squares and this tells me it is time for new darks.

Clive if you can do -20 or -25C all year around then do that.
Exactly my experience with the same camera. 90 percent of the time I run at -20C and in summer -15C usually with 5 or 10 min subs.
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  #48  
Old 21-10-2012, 09:44 AM
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Originally Posted by allan gould View Post
Exactly my experience with the same camera. 90 percent of the time I run at -20C and in summer -15C usually with 5 or 10 min subs.
Hi Allan,
Does this mean that you're scared to take it colder?
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  #49  
Old 21-10-2012, 11:59 AM
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My qhy9 ccd chip cracked the 4-5th time I used it. Catch you later $400. It was being cooled to -25C. I had maxim using the warm up feature but that still didn't help. I was told later that the kaf8300 chip should not be cooled below -10 as it dramatically increases the chance of cracking.

I don't understand how people get to -62 and don't have their chips explode.
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Old 21-10-2012, 12:38 PM
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Originally Posted by nobbygon View Post
My qhy9 ccd chip cracked the 4-5th time I used it. Catch you later $400. It was being cooled to -25C. I had maxim using the warm up feature but that still didn't help. I was told later that the kaf8300 chip should not be cooled below -10 as it dramatically increases the chance of cracking.

I don't understand how people get to -62 and don't have their chips explode.

Thanks for the heads up.
I won't cool mine to the maximum anymore.
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  #51  
Old 21-10-2012, 01:38 PM
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Did you just put your hand up to present one at next year's AAIC?

Bolts? Omaroo? Reading this?

Quote:
Originally Posted by ptc View Post
well obviously if you haven't heard of it there are things that are commonly done that you need to learn how to do.. or at least understand what they do and decide if it is appropriate for your usage.

The Cassini and Galileo probes both had light flood to manage RBI. it is implemented in FLI ML and PL cameras too.

Except for FLI and to a lesser extent Apogee, no one else that I am aware of implements light flood. These camera companies are in denial as to the issues associated with RBI and it is a very real phenomenon observed in ALL KAF series sensors: with some significantly worse than others.

Dark shot noise is completely unrelated to bias frames. It is the noise you get by virtue of a non-zero signal level (average) in dark frames. It is numerically equal to the square root of the number of electrons in the frame.

So 100 electrons per pixel of average dark signal level means you have 10 electrons of dark shot noise. This is random noise like read noise. so you manage it by averaging many frames together. For dark signal you can do one better and that is by cooling... so you can make it smaller in a per frame basis by cooling or you can average many frames together to 'beat it down' (like read noise).

When you take 4x the frames then you get to reduce the noise by a factor of two....

sounds like some of you guys could benefit from my basic lecture series of the basics of electronic imaging... noise sources, management thereof and how to get high SNR images and how to tell when good enough is good enough!


Keep in mind that if you are imaging something faint where read noise is a consideration, then dark shot noise will also be a consideration and if you cannot run as cold as you would like to keep the dark shot noise less than the read noise, you may be better off to reduce your exposure time and take more exposures....

this stuff isn't terribly complicated but there are a few basics that I cover in my lecture series that I think anyone that is serious about imaging ought to know... sort of like the basics of how an internal combustion engine works and the importance of lubrication, gearing and tires by way of analogy....
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