How stable are uncooled DSLR temperatures?

[Stub Mandrel]

I've just done a mind numbing trawl through a few hundred EXIFs.

As you can see the EXIF data is mostly in steps of 2 degrees, except from 17 to 18 degrees. so afirly crude but you can see taht teh 'stbilisation' period for the camera is about an hour.

The light trace is from the camera, which had been given about 5-10 minutes cooldown since the previous run, then took nearly two and a half hours of subs, all uncooled. It took an hour to warm up by two degrees, then presumably dropping external temperatures took it down two degrees again.

I then moved the camera into (unheated) shelter and put it on a wooden chair to take two hours of darks. Clearly I should have left it out in the open, or at least where air could flow round it.

 

The message seems to be that, once the camera is warmed up the temperature does remain pretty stable.

It also suggests that if I group darks by temperature and build up a library, then I can 'pull out' those from a range comparable with the range for my lights. So for the above session I could just use the 13 and 15 degree darks and save the 17/18 degree ones for use with lights taken on warmer evenings.

[almcl]

That's interesting, Neil.

My own experiments (a little while ago now) with the 700d showed a much greater range of temperatures (40°C down to 23°C on one run).  I also did some measurements with a remote reading infra red thermometer.  These didn't agree very well with the exif data, although the trend (up or down) was reflected.

Using a clip filter made quite a difference, too.  Without it, I guess the cool, dew laden, night air could get to the sensor at prime focus on my Newtonian quite easily but once it's in place (pretty much a necessity in my light polluted back garden) the sensor stays warmer for longer. 

Do you have any filters (or other bits) in place or is your sensor 'exposed' ?

[Thalestris24]

Hi

I don't think the exif value (at least, the temp that APT includes with the file name - I assume that's the exif temp?) reflects the actual sensor temperature. With my cooled 550d the file name temp is maybe 14 deg when the sensor is cooled to 5 deg. Presumably the temperature sensor itself is not directly connected to the image sensor? The 14 deg recorded temp is, however, below the ambient temperature by a number of degrees.

Louise

[Stub Mandrel]

2 hours ago, almcl said:

That's interesting, Neil.

My own experiments (a little while ago now) with the 700d showed a much greater range of temperatures (40°C down to 23°C on one run).  I also did some measurements with a remote reading infra red thermometer.  These didn't agree very well with the exif data, although the trend (up or down) was reflected.

Using a clip filter made quite a difference, too.  Without it, I guess the cool, dew laden, night air could get to the sensor at prime focus on my Newtonian quite easily but once it's in place (pretty much a necessity in my light polluted back garden) the sensor stays warmer for longer. 

Do you have any filters (or other bits) in place or is your sensor 'exposed' ?

I've got a coma corrector so the lens is completely enclosed.

bear in mind the camera had been settles with a 2-hour+ run on another target so the initial temperature isn't far off the stable one.

[Stub Mandrel]

1 hour ago, Thalestris24 said:

Hi

I don't think the exif value (at least, the temp that APT includes with the file name - I assume that's the exif temp?) reflects the actual sensor temperature. With my cooled 550d the file name temp is maybe 14 deg when the sensor is cooled to 5 deg. Presumably the temperature sensor itself is not directly connected to the image sensor? The 14 deg recorded temp is, however, below the ambient temperature by a number of degrees.

Louise

It's a Canon 450D, the air temperature was well below 10 degrees C so I'm happy to assume that the Exif temperature is the sensor temperature or close enough to it as that's what most people interpret it as.

[almcl]

I envy you your stable temperatures!

You may well be able to get a dark library to work, especially if you are doing that enclosed.

Here's a sample of my exif data from the other evening.  As you can see the range of temperatures makes darks a bit problematic:

 2016/09/25 20:29:48 IMG_1735.CR2    M    241s ISO:1600               Canon 700D Temp:42C  
2016/09/25 20:36:45 IMG_1736.CR2    M  301.2s ISO:1600               Canon 700D Temp:41C  
2016/09/25 20:42:53 IMG_1737.CR2    M  301.3s ISO:1600               Canon 700D Temp:35C  
2016/09/25 20:48:45 IMG_1738.CR2    M  361.7s ISO:1600               Canon 700D Temp:32C  
2016/09/25 20:54:48 IMG_1739.CR2    M  361.6s ISO:1600               Canon 700D Temp:26C  
2016/09/25 21:03:30 IMG_1740.CR2    M  361.7s ISO:1600               Canon 700D Temp:30C  
2016/09/25 21:09:33 IMG_1741.CR2    M  361.6s ISO:1600               Canon 700D Temp:25C  
2016/09/25 21:20:18 IMG_1742.CR2    M  361.7s ISO:1600               Canon 700D Temp:20C  
2016/09/25 21:26:21 IMG_1743.CR2    M  361.7s ISO:1600               Canon 700D Temp:22C  
2016/09/25 21:32:23 IMG_1744.CR2    M  361.7s ISO:1600               Canon 700D Temp:22C  

[Stub Mandrel]

43 minutes ago, almcl said:

I envy you your stable temperatures!

You may well be able to get a dark library to work, especially if you are doing that enclosed.

Here's a sample of my exif data from the other evening.  As you can see the range of temperatures makes darks a bit problematic:

 2016/09/25 20:29:48 IMG_1735.CR2    M    241s ISO:1600               Canon 700D Temp:42C  
2016/09/25 20:36:45 IMG_1736.CR2    M  301.2s ISO:1600               Canon 700D Temp:41C  
2016/09/25 20:42:53 IMG_1737.CR2    M  301.3s ISO:1600               Canon 700D Temp:35C  
2016/09/25 20:48:45 IMG_1738.CR2    M  361.7s ISO:1600               Canon 700D Temp:32C  
2016/09/25 20:54:48 IMG_1739.CR2    M  361.6s ISO:1600               Canon 700D Temp:26C  
2016/09/25 21:03:30 IMG_1740.CR2    M  361.7s ISO:1600               Canon 700D Temp:30C  
2016/09/25 21:09:33 IMG_1741.CR2    M  361.6s ISO:1600               Canon 700D Temp:25C  
2016/09/25 21:20:18 IMG_1742.CR2    M  361.7s ISO:1600               Canon 700D Temp:20C  
2016/09/25 21:26:21 IMG_1743.CR2    M  361.7s ISO:1600               Canon 700D Temp:22C  
2016/09/25 21:32:23 IMG_1744.CR2    M  361.7s ISO:1600               Canon 700D Temp:22C  

Waht are you using to gat neat list like that? KUSO makes me have to scroll down and read it from each image one at a time :-(

[Thalestris24]

2 hours ago, Stub Mandrel said:

It's a Canon 450D, the air temperature was well below 10 degrees C so I'm happy to assume that the Exif temperature is the sensor temperature or close enough to it as that's what most people interpret it as.

Hi

You have to bear in mind that doing long exposures heats the sensor even if the general camera environment is cool. Doing lots of long exposures obviously heats the sensor even more. I suppose it's not a problem if you live in Norway or Finland!

Louise

[almcl]

13 hours ago, Stub Mandrel said:

Waht are you using to gat neat list like that? KUSO makes me have to scroll down and read it from each image one at a time :-(

After a couple of false starts, I settled on exiflog http://www.covingtoninnovations.com/dslr/exiflog.html 

You have to save it as text file to use it in posts but I find it invaluable for working out where my lights end and the flats start :-)

[Stub Mandrel]

Thanks :-)

I just did a quick look at 29 subs of the flaming star nebula, they are all 13 degrees.

That will be a godsend, I can now compile a library of darks for each temperature and even split subs into DSS groups by temperature!

I think I need a new terrabyte HDD just for all the programs I have downloaded for AP!

[Ouroboros]

21 hours ago, Stub Mandrel said:

It also suggests that if I group darks by temperature and build up a library, then I can 'pull out' those from a range comparable with the range for my lights. So for the above session I could just use the 13 and 15 degree darks and save the 17/18 degree ones for use with lights taken on warmer evenings.

I have done just this. I use BackYard EOS software to gather lights, darks and bias data.  It saves files with the temperature in the name so that darks can be listed according to temperature, although they were taken during different image sessions. It's very quick and convenient when loading files into DSS to select darks in more-or-less the same temperature range as the lights. It's worked for me wih my moderate imaging ambitions  but I susoect purists and more exacting imagers might consider it an unsatisfactory approach.