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Old 12-08-2013, 05:39 PM
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Advertised versus actual CCD cooling performance

My SBIG STF-8300M seems to reliably achieve 30 deg C cooing below ambient air temps at 90% power, but SBIG's "typical" specifications state that it should achieve -36 deg C at 80% power.

I've queried SBIG about this when my camera was sent in for warranty repair (defective cooler, oddly enough), and they claimed that this level of cooling was "within spec".

I'm curious about how other people's cameras go in terms of specified vs actual cooling performance?
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Old 12-08-2013, 06:14 PM
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Bassnut (Fred)
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mmm, my STXL6303 gets to -35deg easily even with 20 or so ambient. My ST10XME on the other hand struggles with -15 year round, I use -10 in the summer. Times have changed though, and -35 should be achievable with newish SBIGs. Also, BEWARE, my cam (I dont know if any other newish SBIGs are the same) CANT go below -35, its designed that way for some odd reason to do with dessicant reliability. In practice, with good darks, -30/35 deg is fine.

If its fine at -35 and cant get -36, the above would explain it. Im happy at -30/35 BTW, not a biggy. Whats your ambient?.
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Old 12-08-2013, 06:17 PM
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mill (Martin)
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My QHY9 with the 8300 chip will make the stated -50C below ambient at 90% power.
Normally i cool to -30C at 35% power but then again the QHY9 has a double stacked peltier.
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Old 12-08-2013, 06:45 PM
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My Apogee Alta U16M with D09 back easily does the 60-65C below ambient that they claim...
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Old 12-08-2013, 07:54 PM
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+1 on the Apogee U16MD09 (F16MD09 in my case). Best I got it down to was -59c below ambient. I normally run it at -30c but I know I should be running it much deeper.
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Old 12-08-2013, 09:40 PM
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My SXVR-M25C easily does 30 below ambient. Not the coldest camera, but gets the job done.

Can't remember how low the SBIG ST8XE went - I recall it was QUITE low, and that was without the water cooling.
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Old 12-08-2013, 10:28 PM
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Thanks for your input, everyone. It seems like with other brands, at least, it would be reasonable to expect to achieve the specified cooling performance.

I wasn't sure whether it was like laptop battery life specifications, i.e. complete and utter lies

I might have to follow up with SBIG again (I was already planning on it regarding problems with bias frames). With long exposures, I can see a very noticeable different in calibrated long exposure subs between -10 deg and -15 deg... hence missing out on the last 5 degrees or so does make a noticeable difference in my case.

Quote:
Originally Posted by mill View Post
My QHY9 with the 8300 chip will make the stated -50C below ambient at 90% power.
Normally i cool to -30C at 35% power but then again the QHY9 has a double stacked peltier.
Wow, that's quite impressive - big plus for the QHY9. Cooling to -30C in my case would require ambient temps of around freezing, clear skies, and 80-90% cooler power - rarely possible even at my dark site out west.
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Old 13-08-2013, 01:42 PM
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Quote:
Originally Posted by Bassnut View Post
Also, BEWARE, my cam (I dont know if any other newish SBIGs are the same) CANT go below -35, its designed that way for some odd reason to do with dessicant reliability. In practice, with good darks, -30/35 deg is fine....
This is correct.

SBIG have put absolute temperature limit of -35 on STX models due the Kodak Chip spec, and at very low temps the chamber will pull moisture from the dessicant rather than the other way around.

Depends on the sensor as well, I've had my STT8300 running happily at -40C in winter, but in practice saw zero difference in S/N to frames captured at -35C

At these temps, cosmic rays prove to be far more troublesome than trivial amounts of thermally liberated electrons
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Old 19-08-2013, 01:29 PM
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Yeah that's right. -30C is a good temp for year round so you only have one set of dark libraries. Modern chips are clean at -30. If not it'd be the support electronics not the sensor. I don't really see a gain at -40 and have also used that at times on an 8300 chip. It usually is clean at -15C.

If you were using RBI control you want the lowest reliable temp as the IR flush causes noise to leak out during the exposure and lower cooling reduces that effect. -35C should be plenty though.

Have you seen a need for RBI on the 6303 Fred? I believe it may be one of the chips that may need it sometimes.

I have only seen RBI a few times on the 16803 - when bright plane lights intersected an image and then the next 2 subs showed a faint line in the same spot that faded out after 2 or 3 subs.

Low temps like -35C make those vertical lines fade out as well. So that's quite an advantage to be able to achieve those low temps.

Greg.
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