Sensor heat during darks

[raymo]

Can anyone tell me what happens to the sensor temp when taking darks? Does the fact that no photons are hitting the sensor make any difference to the amount that the sensor heats up? In other words, do I need to have some cooling time between subs when using in camera
noise reduction, where the camera takes a dark after each sub?
raymo

[glend (Glen)]

I will assume your talking about DSLRs here. Personally I don't use camera noise reduction, because I saw a recommendation on Canon EOS camera setup for astro photography that recommended it be turned off. I don't allow camera managed darks during the imaging run, but I do my darks before or after the run using my remote. I do the offset/bias frames after the darks using the fastest setting available on the camera 1/4000th. Between the dark and the offset/bais frames they provide a pretty good noise reduction set for DSS to work with, don't they? I am having pretty good results doing it this way and my camera (450D) does not get hot at all. I only have to allow about a 10 second interval between exposures for the camera to get ready for the next shot (ie the liveview screen number in the bottom right stops flashing - flashing indicates it is still busy saving the file I think).

[leon]

In Regards to ICNR, Although it takes twice as long to do an imaging run I found it to be the best option, one is then closest to the ambient temp of the lights.
Agreed, it is a pain to stand around for all that extra time, but the results for me at least were worth it.

And yes the flashing red light dose indicate that the camera is not yet ready for the next frame.

Leon

[raymo]

Thanks Glen and Leon for your replies, although neither response
actually answers my question. I set my intervalometer to take, say,
60sec subs, leaving 65 secs between each one, to allow time for the camera to do it's noise reduction thing. I am therefore
effectively allowing 5 secs cooling time. What I want to know is
whether the sensor continues to warm up while the camera is taking the noise reduction dark sub. If it does, then it seems that I should allow significantly more cooling time.
raymo

[RB (Andrew)]

Originally Posted by raymo

What I want to know is
whether the sensor continues to warm up while the camera is taking the noise reduction dark sub. If it does, then it seems that I should allow significantly more cooling time.
raymo

Yes I would leave at least 20 to 30 sec (I think I used to leave 45 sec) for sensor cooldown since the sensor continues to heat up during the dark frame cycle.
Now I do manual darks not ICNR (In Camera Noise Reduction) and I still leave time for the sensor to cool down.
(Another thing I do is turn off the preview screen or at least have only quick previews because that too produces heat).
Also I prefer to use an external 240v powerpack for the DSLR not the internal battery since again the internal battery creates heat during use.

Andrew

[raymo]

Thanks Andrew, that's what I needed to know.
raymo