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  #21  
Old 10-10-2011, 09:43 AM
jase (Jason)
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Also Richard....

What is your opinion of cooling and longevity of the CCD chamber seal? I'm aware many (telescope rental companies and education institutes) don't warm up the cameras during the day light hours as by doing so it apparently prolongs the longevity of the CCD chamber seal.

Fact or Fiction?
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  #22  
Old 10-10-2011, 11:24 AM
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It is an interesting thread. I run my ML8300 either at -35C or -40C. There are a few hot nights in summer where it may struggle to achieve -40C but it always will reach -35C in less than 5 minutes.

The Proline I also run at -35C and it achieves that again almost all year round except for the odd really hot summer night which is not that common for me. I have run the Proline at -40C in winter but as mentioned there is no discernible difference and -40C isn't
achieveable all year round.

I noticed originally when I had an STL11 how much cleaner the image was when on those rare cold winter nights I could get it to go to -35C.
It certainly was the sweet spot for that particular camera.

Dark noise is never an issue with my images from these FLI cameras.
They are close to noise free but there is still some slight improvement from darks.

Jase I would be going for lower temps with your D09. It has powerful cooling.
The only thing that may get in your road is the firmware. It is designed to work out its
own setpoint. So you could tell it to go to -40C and it should but the firmware may kick in
if the % power is beyond its programmed setting (80%?? - ask Apogee what they set it to).

My U16M would do that occassionally which can upset an imaging run if you are not expecting it.
I suppose though it will happen in the first 35 minutes. That's when I asked it to achieve too high
a cooling number but my one was the standard cooling package not the D09. I never saw a voltage
warning either. But then the D09 no doubt draws a lot more power. Perhaps it is a firmware issue
rather than an actual voltage issue.

I had a vertical line which is common with 16803 chips develop about 2 months ago where there were none.
I have a particularly clean chip which was hand picked. Fresh darks got rid of it. Also these lines as Richard
pointed out fade with heavier cooling and are less of an issue. They used to drive me crazy with my STL11
as they sometimes would not dark subtract out with that camera for some odd reason. Perhaps I did something
wrong with the dark subtract.

Greg.
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  #23  
Old 10-10-2011, 04:43 PM
Alchemy (Clive)
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Quote:
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.
It would appear my camera doesn't have some of the features discussed.... Meh .... Can't have everything

Quote:
Clive if you can do -20 or -25C all year around then do that
.

That would seem to be the general consensus from those who've replied, I did a stretch on my darks and couldn't see anything out of the ordinary, so summer will be 20 and I might drop it when it cools, and do the dark library like jase every 3 months or so.

Whilst the uber tuning of things is possible, I'm not running a formula 1 machine so I won't get too upset by minor imperfections.
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  #24  
Old 10-10-2011, 07:36 PM
ptc (Richard)
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Quote:
Originally Posted by gregbradley View Post
Also these lines as Richard
pointed out fade with heavier cooling and are less of an issue. They used to drive me crazy with my STL11
as they sometimes would not dark subtract out with that camera for some odd reason. Perhaps I did something
wrong with the dark subtract.

Greg.

The dark lines are usually caused by a partially blocked column that results in a 'skim' or more properly, a deferred charge.

You did nothing wrong: unfortunately they will neither dark-subtract or flat field out. They usually are small so the best bet is combining deep cooling with a dithering of aiming between shots and a combining algorithm such as median or some other method that rejects "flyers"

the cooling will minimize the badness associated with these traps and the dithering and combine method will eliminate them from the final processed image.
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  #25  
Old 10-10-2011, 07:51 PM
ptc (Richard)
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Quote:
Originally Posted by jase View Post
Also Richard....

What is your opinion of cooling and longevity of the CCD chamber seal? I'm aware many (telescope rental companies and education institutes) don't warm up the cameras during the day light hours as by doing so it apparently prolongs the longevity of the CCD chamber seal.

Fact or Fiction?
I don't think there's a single answer that is true for all designs.

It really depends on how the camera and seal are made

I can say that leaving the sensor biased up 24/7 will increase the liklihood of random radiation damage.

The sensors are bombarded constantly by radiation. ]Under the right circumstances some of it can cause hole-electron pair generation in the gate oxide. This is very undesirable, but the damage can be self-repairing (annealing) under the right conditions.

when an energetic particle passes through the gate oxide and collides with atoms in it, it loses energy and that can create hole-electron pairs within the gate oxide. If these oppositely charged "particles" remain physically close to each other, there's a statistical probability that they will recombine, and if they do there's no lasting damage.

However the hole has very low mobility compared to the electron and what often happens is that the electron is swept away by an electric field (like if the sensor is under bias) and that leaves a hole trapped in the gate oxide. That causes a shift in the flatband voltage if enough of them are so trapped and that can cause the sensor's dark current to increase significantly in pixels so damaged.

Leaving the sensor under bias simply increases the probability that the recombination does not happen. So if you have two identical sensors sitting next to each other, one powered up and one not, the one that is powered up will age faster than the other one....

It is certainly possible to design a camera that can be cooled separately from powering up the electronics, so in theory it should be possible to leave one cooled down but not under bias, so as to minimize the risk, but none of the amateur Astrocams I have seen work that way.

the FLI ML and PL cameras have very good seals. Thermally cycling them seems to have no effect on the integrity of the seals.

I've heard that the reason Apogee takes a half hour to cool down is out of concern of the integrity of their seals. I haven't personally compared the design of the seals of the two brands to see how they differ. I suspect that the Apogee seal design is reasonably robust and using a half hour to cool down is being unnecessarily conservative from the perspective of chamber seal integrity.

Perhaps there's another reason for the long cool down like thermal runaway?
That's poked its ugly head up occasionally in certain camera designs in the past. One thing is certain; the fans aren't arranged in such a way to efficiently shed heat from the heatsink in the Uxxx designs: the fans' airflow stagnates at the bottom of the heatsink in the one I examined.

From a marketing perspective, it seems easier to swallow telling someone to accept slow thermal slews to keep the chamber seal good than to prevent thermal runaway....

claiming the former will tend to cast doubt on the operational integrity of your competitor versus the latter which reveals a design deficiency in your own product: two different ways to spin the same issue....
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  #26  
Old 10-10-2011, 07:55 PM
ptc (Richard)
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[QUOTE=Alchemy;773214]
That would seem to be the general consensus from those who've replied, I did a stretch on my darks and couldn't see anything out of the ordinary, so summer will be 20 and I might drop it when it cools, and do the dark library like jase every 3 months or so.
QUOTE]

keep in mind that groupthink is often wrongthink: witness "The earth is flat" belief from yesteryear.

the only way to know for sure is to measure the dark signal under the planned exposure conditions (exposure time and temperature) and compare to the read noise and background signal levels.... that of course is neglecting RBI
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  #27  
Old 10-10-2011, 07:57 PM
ptc (Richard)
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Quote:
Originally Posted by jase View Post
Voltage

When you are running the camera near 95%, what is the voltage draw? If I hit 95%, I get a low voltage warning as the TEC consumes considerable power. Running at constant 98% or more, the camera becomes unstable. I've ensured the camera has ample power, I've even connected it to a regulated 12vdc 10amp source, same result.
sounds like you have a problem with the design of the camera or power supply.

there's no good reason that a properly designed camera and or power supply cannot run at full load and behave properly.

what are you using Jase?
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  #28  
Old 11-10-2011, 02:24 AM
jase (Jason)
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Quote:
Originally Posted by gregbradley View Post
....
Jase I would be going for lower temps with your D09. It has powerful cooling. The only thing that may get in your road is the firmware. It is designed to work out its own setpoint. So you could tell it to go to -40C and it should but the firmware may kick in if the % power is beyond its programmed setting (80%?? - ask Apogee what they set it to).

My U16M would do that occassionally which can upset an imaging run if you are not expecting it. I suppose though it will happen in the first 35 minutes. That's when I asked it to achieve too high a cooling number but my one was the standard cooling package not the D09. I never saw a voltage warning either. But then the D09 no doubt draws a lot more power. Perhaps it is a firmware issue rather than an actual voltage issue.
....
Greg.
You're right Greg, I should be pushing the camera harder. A set point of -40c all year round is certainly achievable with the D9F cooling, undoubtedly lower in winter. The voltage problem isn't firmware related. Apogee would have advised if it were given the camera came back from a routine service a few months ago. I suspect it is power related. The power supply I have is not Apogee certified, but a third party of similar output. The original fried a while ago. I think I'll place an order for another original to see if this alters the situation.

===

Richard,
Thanks a lot for your comprehensive input and opinion on the CCD chamber seals. Not doubted your knowledge as I know you work with these CCD's all day long, but there are a lot of hypothetical and probabilities as one could expect. Its so darn hard to get a clear statement from any manufacture on the topic...and I guess...who cares when they offer lifetime warranty on the chamber seal anyway. I think you nailed it in your opening two sentences, though I'm still intrigued to the logic and reasoning of others. I agree with your statement regarding a camera powered up will age faster. Though you can apply the same logic to owning a car. A car you leave in the garage will last longer than the one your drive around. I've had to replace a few fans, no different to tires on a car.

Quote:
Originally Posted by ptc View Post
It is certainly possible to design a camera that can be cooled separately from powering up the electronics, so in theory it should be possible to leave one cooled down but not under bias, so as to minimize the risk, but none of the amateur Astrocams I have seen work that way.
What is the reasoning manufacturers haven't done this? Manufacturers make the assumption that ALL users cool and turn off their camera each session?

Quote:
Originally Posted by ptc View Post
One thing is certain; the fans aren't arranged in such a way to efficiently shed heat from the heatsink in the Uxxx designs: the fans' airflow stagnates at the bottom of the heatsink in the one I examined.
Yes, I can understand that. You are obviously referring to the non-D9F configuration of the Uxxx designs. At least I hope you are, as you would also be implying the FLI PL isn't efficient. The Apogee D9F configuration is near identical as the FLI PL with the three fans blowing air through the heat sink. The only difference being the Apogee D9 has a larger heat sink than the FLI PL in both depth and width, but the heat sink/air flow design is fundamentally the same.

Quote:
Originally Posted by ptc View Post
sounds like you have a problem with the design of the camera or power supply.

there's no good reason that a properly designed camera and or power supply cannot run at full load and behave properly.

what are you using Jase?
Power supply. See note above to Greg's response. I'll order an "official" replacement power supply from Apogee. What I've got works, but there is no way I could operate at 95% cooling power with the current supply. I pushed the camera last night and achieved 48C below ambient but MaximDL was reporting 10.9V UNDERVOLTAGE. I've got a lab report for the camera that indicates it was tested out as 62C below ambient so I'm assured its not the camera...time to get ordering.
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  #29  
Old 11-10-2011, 04:25 AM
ptc (Richard)
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Quote:
Originally Posted by jase View Post
Yes, I can understand that. You are obviously referring to the non-D9F configuration of the Uxxx designs. At least I hope you are, as you would also be implying the FLI PL isn't efficient. The Apogee D9F configuration is near identical as the FLI PL with the three fans blowing air through the heat sink. The only difference being the Apogee D9 has a larger heat sink than the FLI PL in both depth and width, but the heat sink/air flow design is fundamentally the same.



Power supply. See note above to Greg's response. I'll order an "official" replacement power supply from Apogee. What I've got works, but there is no way I could operate at 95% cooling power with the current supply. I pushed the camera last night and achieved 48C below ambient but MaximDL was reporting 10.9V UNDERVOLTAGE. I've got a lab report for the camera that indicates it was tested out as 62C below ambient so I'm assured its not the camera...time to get ordering.
yes the non-D9 Version... the D9 has adopted a non-stagnating configuration for the fan/heatsink as was a feature of the PL and ML from FLI from the get-go

As for your power supply issue: it is disappointing to spend a fortune on a camera to later discover they have a power supply that doesn't measure up to the task for which it was assigned. It may be that the better cooling offered by the D09 option uses more current than the original configuration and that they failed to account for that by shipping with the same old power supply.

It could be a simple oversight but it is nonetheless disappointing to spend that much money and get less than what you paid for.

For the record the FLI cameras have no such anomalies even at 100% power. They have no cooling headroom at 100% of course but they at least supply sufficient current and work correctly there.

Again I regularly operate mine at 95-97% power with no bad effects. For my 39Mpixel with its two output amplifiers, any sort of error in cooling will reveal the seam from the two sides... it is that sensitive to dark signal/dark cal frame mismatches.
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  #30  
Old 11-10-2011, 10:33 AM
jase (Jason)
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Thanks Richard.

Are you going to answer my previous questions or simply fly the FLI flag?

You sure are quick to make assumptions. Suggest you read the facts in future. The current power supply in use didn't even come from Apogee. You are welcome to still hold them erroneously accountable but whatever you do don't get disappointed, I'm certainly not! In fact I find it remarkable how resilient the camera is being able to drop 48C below on a bad power source (only 14C off lab benchmark of 62C below).

Last edited by jase; 11-10-2011 at 04:59 PM.
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  #31  
Old 11-10-2011, 12:30 PM
Alchemy (Clive)
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..

Last edited by Alchemy; 11-10-2011 at 04:14 PM.
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  #32  
Old 11-10-2011, 01:05 PM
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What is RBI?
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  #33  
Old 11-10-2011, 01:22 PM
jase (Jason)
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What is RBI?
http://www.ptbmagazine.com/features/...eat1_0409.html

Courtesy of Richard himself.
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  #34  
Old 11-10-2011, 05:02 PM
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Thanks Richard.

Are you going to answer my previous questions or simply fly the FLI flag?

You sure are quick to make assumptions. Suggest you read the facts in future. The currently power supply in use didn't even come from Apogee. You are welcome to still hold them erroneously accountable but whatever you do don't get disappointed, I'm certainly not! In fact I find it remarkable how resilient the camera is being able to drop 48C below on a bad power source (only 14C off lab benchmark of 62C below).
He he Richard is one of a kind

Delta 62C huh? that's not bad , my PL11002 could do that but not my PL16803 (bigger chip) - from a quick test on a summer afternoon last year it could only go 58C delta.

Mike
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  #35  
Old 11-10-2011, 06:30 PM
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I reckon I could use the frankenfridge to supply -15C liquid coolant to my PL16803. Lets see delta 58C plus -15C is -73C!
Bert
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  #36  
Old 11-10-2011, 08:24 PM
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I reckon I could use the frankenfridge to supply -15C liquid coolant to my PL16803. Lets see delta 58C plus -15C is -73C!
Bert
Not sure if chilled liquid coolant is a good idea Bert. The manual for my camera repeatedly says not to use water cooled below below the dew point when using liquid cooling as the heat exchanger mounted on the camera will potentially drop below the dew point. This will lead to condensation on the camera which might fry the electronics.

DT
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Old 11-10-2011, 09:10 PM
ptc (Richard)
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Not sure if chilled liquid coolant is a good idea Bert. The manual for my camera repeatedly says not to use water cooled below below the dew point when using liquid cooling as the heat exchanger mounted on the camera will potentially drop below the dew point. This will lead to condensation on the camera which might fry the electronics.

DT
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!
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Old 11-10-2011, 09:16 PM
ptc (Richard)
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well glory be! I didn't know that was online!

here's a more recent publication, this time done through SPIE (Society of Photo Optical Engineers)

http://www.narrowbandimaging.com/inc...14293318_1.pdf

the article was written in 2008 and for some reason the SPIE wizards lost it for three years. Better late than never I suppose....

Hey, sorry about missing your comment about the power supply. I had arrived in Korea yesterday after traveling about 22 hours from the US connecting through Taiwan. Sometimes I amaze myself as to what I fail to see when I am so jet-lagged!

anyway, point taken that you are using a different power supply versus what Apogee supplies with the camera.
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Old 11-10-2011, 09:42 PM
ptc (Richard)
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What is the reasoning manufacturers haven't done this? Manufacturers make the assumption that ALL users cool and turn off their camera each session?
I can only speculate... First of all I haven't seen any evidence that thermal cycling damages seals: I've heard claims made by Brown of Apogee, but that could be an excuse to avoid fixing a thermal runaway problem while at the same time casting doubt on the integrity of the designs of his competitors as I mentioned yesterday. Clearly the air cooled Uxxx series has an airflow stagnation problem as we discussed. That obviously makes heat removal from the heatsinks less efficient than the way the Proline does it and the way the D09 does it (that appears to have adopted the same method used by the Proline which did it that way several years before the D09 was introduced). One thing is certain, it is a lot easier to make up a cock and bull story than it is to:
1) redesign the fans/heatsinks, test and deploy (cost $$$$)
2) deal with angry customers that want the 'fixed' version for free (and rightly so....)

it is much easier to claim you are the only one doing it right and the other guys are not... so long as no one can prove you are lying, of course....

So this entire 'thermal cycling causes seal damage' theory may be a case of chasing phantoms. But true or not, it should not be a big deal to change the control circuitry/microcontroller firmware to let the cooler run without turning on the clocks and power to the sensor.

Knowing the way the FLI guys operate, if anyone would be willing to do a customization, they would. I suspect all would do it if they thought it would bring in more business... But I rather strongly suspect this entire thesis about seals is a red herring. I'll go on record saying that I don't buy it and I have used lots of fancy cameras with big sensors over the years, and simply flip the switch off when I am finished: no damage...

I am currently overseas on biz but I have some reference material about the issue with ionizing radation/recombination for biased versus non-biased sensor storage that I should be able to make available. That is most definitely NOT a red herring.... however it will be about two weeks before I am home again and have access to my library

It would be a shame to see these observatory fellows damaging their sensors from radiation damage (leaving powered up) in order to avoid a suspected chamber seal hermeticity problem that really is a non-existent problem and was simply spin put forth by a cynical vendor that wants to avoid being held accountable for fixing what clearly is a demonstrable weakness in the cooling system mechanical design.

you can say what you want but Apogee's cooling behavior is singular in the industry and since I haven't seen a pile of trashed cameras sporting damaged seals or cracked sensors (their earlier party line position that they have since abandoned) from thermal cycling, I dare say there's more evidence piling up against the Apogee party line being true than evidence in support of it....

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Old 12-10-2011, 12:54 AM
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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.
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