Re: Cooling time for CCD cameras ... test without light

[George McNamara]

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Hi Esteban,

As others have noted, cooling is pretty quick. You do NOT want to do
this with a fluorescent specimen - you would be getting both
photobleaching and camera cooling.

Cooling affects the dark current, rule of thumb is dark current
decreases with every ~7 C of cooling. A simple test - I'll use MetaMorph
as an example:

1. Start everything, except the camera (MetaMorph will typically
complain about the camera, just say no to try again).
2. Configure the exposure time to 1 ms (Acquire image command).
3. Create a journal and taskbar button to do Acquire Timelapse, say one
exposure per second, 5 second interval, for (say) 15 minutes, to stack
-- or disk if you want more data. Make the Taskbar visible so you can
clikc on the journal button immediately after starting MetaMorph next time.
4. Setup the light path so NO LIGHT goes to the camera (or put the lens
cap on).
5. Exit MetaMorph.
6. Turn on the camera, immediately start MetaMorph, click the journal
button. When done, save the data. Simplest to use Apps - Graph
Intensity, but Measure Regions is fine.
7. Go have lunch.
8. Close the stack or change the file save name and/or path.
9. Acquire another timelapse after the camera has fully cooled.

On my ORCA-ER(s), starting intensity is around 300, takes a couple of
minutes to reach ~200 (12-bit range). On my ORCA-II ERG, takes longer to
cool to -60 C, offset when cool is ~600 out of 14-bit range.

//

Speaking of timelapse tests - the centenary of the discovery of cosmic
ray particles by Victor Hess is 7 August 2012
(http://en.wikipedia.org/wiki/Cosmic_ray and M. Friedlander 2012 Nature
483: 400-401 do not currently give the date - date from P. Carlson 2012
Physics Today Feb 2012: 30-36). I encourage everyone with a camera that
can be set to "no light" to do either a Friday August 3 (end of work) to
Monday August 4 (start of work) or overnight(s) August 7. No light, max
exposure time for your camera, continuous timelapse. Easiest way to
summarize the dataset is to aet up your software to do a maximum between
the newest image and an "accumulation" image (of course test this before
the big date). I recently submitted a 30,000 frame (ORCA-ER, 10 second
exposures) to one of the microscope company photo contests.

As for what to do with the data - I suggested to one of my colleagues
that they take the lead in posting this request to the listserv. I
haven't seen a post from them (yet). If they decide not to organize
everyone's image, perhaps Esteban will?  If not, I'll consider making a
montage of everyone's accumulation images for posting someplace on the
Internet.

George
p.s. I am not a fan of N=1 experiments, so I want to credit M.
Friedlander (Nature article) for pointing out that:

"In 1932, Carl Anderson was using a Wilson cloud chamber with a large
magnet to study cosmic rays when he observed a particle that had the
mass of an electron, but a positive charge. The discovery of the
positron, as Anderson named the particle, was recognized when Anderson
shared the 1936 Nobel prize with Hess."




On 5/12/2012 5:28 PM, G. Esteban Fernandez wrote:

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>
> Hi all,
>
> 1)  I'm curious how much time, roughly, it takes for a Peltier-cooled
> CCD camera to reach the lowest temperature.  Are we talking a few
> minutes or closer to an hour or more?  I have several brands of cooled
> CCDs of different vintages and I'm just looking for a "rule of thumb",
> if possible.
>
> 2) I do plan to test my cameras myself:  I was thinking of imaging a
> timelapse of a dim&  stable specimen (requiring something like 30-60
> sec. exposure) after turning cooling on to see at what time noise
> reaches a minimum.  Any suggestions for other ways to test this are
> welcome.
>
> Thanks,
> Esteban
>