Thermal Shock!

[PhotoGav]

I had what could have been a total catastrophe last night. I think I've got away with it, but I would like to understand more.

I was happily imaging away (despite the really pretty poor conditions, the subs will probably end up in the bin, but that's a whole different story...) when my iPad check revealed that PHD had lost its star. I presumed cloud, went outside to investigate and saw it was still clear. I looked on the laptop and things were not well at all. PHD had hung and APT was having trouble communicating with the imaging camera. Mount control was still possible though. I panicked somewhat, wondering whether my beloved QSI683 was about to suffer terminal damage. I restarted the laptop and things seemed to be going well, but no joy. Then the QSI went into alert mode and flashed and beeped at me. I read the manual, which suggested the only way out of this one was to pull the power plug and restart the camera. Thoughts of thermal shock went through my mind. The camera had been running at -20°C. I didn't know what it was at now.

It was at this point that I noticed that the USB hub power light was not on... I unplugged all it's connections and plugged them all back on again. I pulled the plug on the QSI, restarted everything and nervously clicked connect to the camera.

Thankfully everything was back up and running properly again now. I cooled the QSI back down to -20, it had got back up to around 5°C in the interim, and finally shot the set of flats that I needed for the night's subs. The flats look completely normal so it appears as though there is no damage at all.

So, the questions are:

How does thermal shock manifest itself?

How does it happen?

How resilient are these cameras to it anyway?

How close was I to killing my baby?

Did I do the right things?

What can I learn from this close shave?!

I look forward to hearing your advice and opinions. Thanks in advance.

Sent from my iPhone using Tapatalk

[Yoddha]

Hi Gav,

Sorry to hear that you had troubles! I can't answer on all question but here is short explanation about how thermal shock happens.

The Peltier element has possibility to transfer heat from the one side to the other, so there is one hot and one cold side when the element is powered. The CCDs usually put a second element to make the delta bigger. When the element is powered off the heat from the hot side goes to the cold side and this happens fast and this is the reason to call it "shock". If this is made frequently the element will start to degrade and not to work efficiently. Maybe if the delta is very big the shock can crack the ceramic plates of the Peltier element... But I never heard one to complain that the camera got broken from one shock...

[PhotoGav]

Ivo, many thanks for the reply and what sounds like much less dramatic repercussions than I had feared... Thank goodness! I will obviously still be careful, but will be slightly less panicked by the whole matter in future.

Still loving APT by the way. How is the next release coming along, are you having time to work on it?

Cheers.

[Yoddha]

You are welcome Gav!

The new version is coming very soon - tomorrow or  in Tuesday BTW there are some QSI specific improvements related to filter profiles

[PhotoGav]

Excellent, look forward to it!