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Old 17-12-2009, 07:00 PM
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Super cooling

I got out last night and did some image..?..YAY!!!!

I needed to do some dark frames for some short exposures I had done last night.

Well...unfortunately it's an oven like +33C in the dinning room isn't it - as per my digital thermometer

I thought oh well I'll give it try any way, so I set the chip temp to -35C which is the usual temperature I operate the camera at all year round and the temp I used last night. After 10min I came back to the dinning table and found the chip temp settled on -30.6 DOH!!!

Still, the camera was able to pull the chip down 63.6C from ambient - not bad huh?

...looks I'll have to wait until near midnight to get an ambient temp that will let me get down to -35C. I did consider putting the whole camera in the fridge buuuut...nahh I'll wait for the cool change

Gotta luv these FLI cameras

Mike
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Old 17-12-2009, 07:14 PM
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pour a few cold beers over it Mike
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Old 17-12-2009, 08:05 PM
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pour a few cold beers over it Mike
I've poured a couple down my throat while I'm waiting....

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Old 17-12-2009, 08:41 PM
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At 9.30pm it is still 32C inside the house, so ....camera's in the beer fridge taking dark frames as I write

Mike
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Old 17-12-2009, 09:06 PM
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-63 delta temp is incredible!! Would definitely love an FLI cam... Few years off I think... Probably a PL16803, or a PL11002M if someone I know decides to go to the 16803 and wants to sell his 11002M

The cooling of the FLI cam's is insane... going purely from tech specs, the SBIG STX range might be similar.. and the Apogee D9 body will cool to -60 from ambient, but it will take half an hour to do so...

Tell me Mike, whats the KAI-11002M like at -35c? darks I've seen at -20c are fairly noisy (compared to what I'm used to seeing from Sony CCD's anyway. I suppose that is probably all suited to a different thread.. but hey.. while we're on the topic of CCD cooling, which is used to control noise, I guess we're still on topic!

Also, on the normal night (say, 19c outside temps) how long does the Proline take to get to the setpoint? a few minutes?
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Old 17-12-2009, 09:14 PM
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Quote:
63 delta temp is incredible!! Would definitely love an FLI cam... Few years off I think... Probably a PL16803, or a PL11002M if someone I know decides to go to the 16803 and wants to sell his 11002M
Ya never know ...although having a back up camera would be good too
Quote:

Tell me Mike, whats the KAI-11002M like at -35c? darks I've seen at -20c are fairly noisy (compared to what I'm used to seeing from Sony CCD's anyway. I suppose that is probably all suited to a different thread.. but hey.. while we're on the topic of CCD cooling, which is used to control noise, I guess we're still on topic!
Here's a 10min dark @ -35C at my web site (large jpeg) downloaded from the camera in a little over a second too:

http://www.pbase.com/strongmanmike20...88167/original

Quote:
Also, on the normal night (say, 19c outside temps) how long does the Proline take to get to the setpoint? a few minutes?
[/QUOTE]

Only a few minutes

Tonight (inside) is the first time in over two years the cooling couldn't get me to -35C but it is a scorcher inside at the moment still 31C and it's after 10pm .

BTW, used the new laptop and new Astroart4 camera control interface last night, can now control multiple cameras at once - very cool.

Mike
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Old 17-12-2009, 09:27 PM
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The dark frame looks very respectable noise wise... KAI-11002M C1 I see smooth..

Yeah I hear you on the "backup camera" idea.. I've been eyeing the ML11002 or the ML3200 as a 2nd camera... but I just cant justify it... If I got the ML11002, I dare say I'd fall in love with the massive field of view, and then rarely ever use the ST8300.. Unless I had 2 scopes and 2 mounts, I think 2 cameras would be excessive..

Tom Davis has the idea, get 2 cameras, both with the same sensor, one mono and one colour.. 2 complementing optical systems, highest resolution scope used with mono camera for luminance while the lower resolution scope used with the color camera to catch RGB info quickly and efficiently...

I have definitely been considering the extreme case of sacrilege I'm going to have when I mate an SBIG camera with an FLI filter wheel... I'm kind of worried that the whole shebang might just spontaneously combust upon screwing it together haha!

Fingers crossed that it all works!!

Great to hear the new laptop is all up and running, ready for imaging!
I got the CFW 2-7 running in MaximDL last night after a few emails with Greg... Although I think I need to buy a plugin from Software Bisque in order to get the CFW running in CCDSoft V5.. Gotta get all this sorted before the camera arrives!!
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Old 17-12-2009, 09:30 PM
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Originally Posted by AlexN View Post

I have definitely been considering the extreme case of sacrilege I'm going to have when I mate an SBIG camera with an FLI filter wheel... I'm kind of worried that the whole shebang might just spontaneously combust upon screwing it together haha!

Fingers crossed that it all works!!
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Old 17-12-2009, 10:15 PM
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Try as I might the best Delta-T I could get with my new camera was around 58C.

Bugger...I forgot! ...I can now re-circulate chilled water over the chamber....make that 80C
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Last edited by Peter Ward; 17-12-2009 at 10:24 PM. Reason: additinal info
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Old 17-12-2009, 10:38 PM
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Quote:
Try as I might the best Delta-T I could get with my new camera was around 58C.
Yeh that's gettin close, much of the 6C less cooling is likely largely because it is a bigger & different chip..? I assume your new camera is a bulky bugger too, huh? Where is that ambient temperature being read from, do you know?

Quote:
Bugger...I forgot! ...I can now re-circulate chilled water over the chamber....make that 80C
Yeh can do that with the FLI's too if you order the body with the water inlets but always thought this idea rather messy and cumbersome, would want to have a dam good reason to do it I think

Mike
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Old 18-12-2009, 04:36 AM
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I used water cooling twice, once with my ST10, once with the ST9, and whilst it does make an appreciable change to the cooling head room, I don't think its worth the hassle of having a bucket next to the mount, around all the power/data leads... Seemed a little dangerous. In an observatory where everything can be neatly organised, I dare say its not too scary, but out in the back yard its disconcerting to say the least...

-53c on the STX is a good result for sure, and 80c would definitely eliminate a bit of noise!!
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Old 18-12-2009, 08:19 AM
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Delta 60C, luxury! The heat of summer is a real pain isn't it Mike. The delta T of a two stage Peltier is about 60C with a small heat load. The delta T you see in the electronic specifications for Peltier arrays are with no load and in a vacuum.

I have ordered an 80l upright freezer and I am going to use it to cool a 50% mixture of antifreeze to about -18C. I will then pump this to the 'hot' side of the peltiers on my camera fridge. This means the camera fridge interior will be able to get to -35C with ease. Even at this fridge temperature (-35C) my sensor will be at -18C.

At the moment the best the fridge can do is about -10C. So sensor temp is 7C.

The first thing to do will be to drill two holes in the new freezers door.

Here is a thread with more detail.
http://www.iceinspace.com.au/forum/s...ad.php?t=54087

We had a saying at CSIRO 'if you begin to doubt your own sanity you are still doing OK'.

Bert

Last edited by avandonk; 18-12-2009 at 08:31 AM.
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Old 18-12-2009, 04:19 PM
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Well my QSI cannot boast those sort of figures. Then again it is a little unit. I think the best I can get generally is around -35C from ambient. This provides some problems on warm nights. I am considering getting the water cooling unit to get me to -45C from ambient.
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Old 18-12-2009, 10:35 PM
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... I am considering getting the water cooling unit to get me to -45C from ambient.
Frankly Paul, I find it all a bit moot.

Delta T's of -58 or -63 are a little meaningless IMHO unless you can also be assured you can get a calibration (dark) frame at exactly the same temperature.

Some manufacturers (no prizes) have CCD chamber temperature stability close to 1/100th of a degree. Others less so, which shows up as post calibration noise.

In my experience with KAF sensors, absolute chip temps of around minus 15 is more than adequate.
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Old 18-12-2009, 11:01 PM
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I guess it depends on where the temp sensor is as well. If it's not inside the sensor, and it's not, then it's all pretty meaningless....
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Old 19-12-2009, 04:40 AM
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As Peter said, careful image calibration is more important than CCD Temp... Whatever noise your sensor has at -15c will be removed if your dark is taken at -15c.

My question is this... What happens if you create a library of darks in a 22 degree ambient temperature, with the camera set at -15c, then you take your images in an ambient temp of 16 degrees with the camera set at -15c? Would the fact that the cooling is doing more work during your calibration images make an appreciable difference when compared to a dark taken at the same time as your imaging, with the same ambient temperatures?
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Old 19-12-2009, 08:04 AM
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Peter I see your point. I have been happy with the dark subtraction so far. The QSI does seem to have good control of this issue.

Alex I don't think this is an issue really. The electronics should be able to handle this type of temperature change and produce darks the same as take at a lower ambient. It's a question that might have some interesting answers though.
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Old 19-12-2009, 08:44 AM
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In my experience with KAF sensors, absolute chip temps of around minus 15 is more than adequate.
Well even if that's true (and you have conveniently over simplified it), the other night a delta T of even 40C wouldn't have got you there at any stage throughout the night ...without a fish tank and pump

Mike
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Old 19-12-2009, 02:49 PM
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As the sensor temperature is lowered not only does dark noise decrease but so does the need for accurate temperature regulation. Once down around -30 C with the KAF chips even +/- 1 C regulation is going to be enough (and dark noise is basically nill).

Terry
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Old 20-12-2009, 08:56 PM
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Quote:
Originally Posted by strongmanmike View Post
Well even if that's true (and you have conveniently over simplified it),
I think, yes, and how?

Quote:
Originally Posted by strongmanmike View Post

the other night a delta T of even 40C wouldn't have got you there at any stage throughout the night ...without a fish tank and pump

Mike
My camera runs a 58C delta T...no problemo....but on nights like that....
the aircon, Scotch on the rocks, and DVD works better for me
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