Nikon D5100 active cooling

[Herra Kuulapaa]

To keep debayering thread more on-topic than off, I start a new one for D5100 cooling. This model has a very good dark current and noise characteristics, which should make it ideal astro-DSLR when cooled. We'll see it though.

Here is the reason why cooling is preferred in Nikon D5100 (and other DSLRs as well):

Horizontal axis is temperature in Celsius and vertical is noise (σK) taken with Pixinsight noise evaluation tool from ISO1600/10min dark frames.

Noise comparison in monocrome to see what it means:

And bigger:

http://www.kuulapaa.com/Tahtidata2/Compare.jpg

So, do your astroimaging when it's nearly freezing outside then and you're on optimal noise level?

Unfortunately not quite because it's getting warmer inside the camera during your photo session despite the environment is for example 0°C (32°F).

Here is a chart of precision temperature meter readings with 0,1°C resolution placed directly on sensor. Horizontal axis is time in minutes and vertical temperature outside camera. D5100 was working on constant imaging with ISO1600/10min frames. We can see that it gets 12°C warmer inside the camera at normal temperatures (0-22°C). When it gets colder the difference is ~5°C (camera sensor and electronics can't warm up cooled body enough to compete thermal transfer out).

[frostynixon]

Hello Herra,

from your graphs above it looks like there`s no real benefit of having a sensor temperature lower than 5° C (-9°C is only 10% better). That`s good news i suppose, because the whole cooling design will be easier. Are you already working on a cooling design? 

greetings

PS: Is the D600 still alive?

[Herra Kuulapaa]

There is a small difference between -5C and +5C. But the main thing is that in my climate I’m imaging during the winter time, it’s not a big effort to cool sensor to -5C or past. Sometimes +5C would require heating

Part 2: A heat transfer element.

There are plenty of active cooling mods available for Canon 550D but practically none for Nikon D5100. Now when the BackyardNikon has been officially released, the D5100’s potential can be fully utilized in astrophotography.

Here are the sensors. 550D on the left and D5100 on the right:

One can right away spot some key differencies. So called cool finger approach cannot be used in D5100 due to the fact that there is no real gap between sensor and circuit board. However it has a clear benefit; a relatively large flat aluminium cooling element, which can act as a platform for copper plate. Internal space in D5100 makes possible to use over 1mm (0.04”) thick copper, so heat transfer should be effective, but I’d recommend not to go much over that thickness. One can get a millimetre more space grinding off those three elevated structures from aluminium element. This gives more clearance to the mainboard.

Easiest way is to mount the cooling element so that the TEC plate comes out of the bottom of the camera. Path is mostly open in that direction.

Next step is to paint cooling element with rubber paint to prevent moisture related short curcuiting and other electrical issues.

[Gina]

When I was using Canon 1100Ds in winter I found just providing a cold finger brought out to a standard CPU cooler was quite sufficient.  Just cooled the sensor to near ambient.  No complicated Peltier TEC cooling involved and no extra electronics

[Herra Kuulapaa]

When I was using Canon 1100Ds in winter I found just providing a cold finger brought out to a standard CPU cooler was quite sufficient.  Just cooled the sensor to near ambient.  No complicated Peltier TEC cooling involved and no extra electronics

Heh, words of reason, never quite listened them

I can't resist posting this same image I did before illustrating well the fact, that practically I wouldn't even need to think about extra cooling.

But, what fun would it be? Instead with TEC I can do all those interesting extra electronics

[Gina]

That's true

[Herra Kuulapaa]

But, it's so true what you said about passive cooling and it should be adequate.

Main idea is also to stabilize dark current for better dark frames, but I have one unmodified D5100 lying around and even cut 1mm copper element ready (it was too short for TEC but suits fine to passive cooling).

[Herra Kuulapaa]

I did some tests yesterday with manually adjusted PWM and TEC-12706. With 1/3 power the sensor was cooled down to -4°C and staid there the whole imaging session.

An interesting observation was that actual exposure doesn't create much heat compared to live view. Difference was very clear and without an active cooling it clearly raises sensor temperature. So I'd recommend keeping the use of it in minimum.

Here's a test with 4x10min Ha, OIII, SII, not quite enough, but a good start for cooled monochrome D5100

[frostynixon]

Wow, very nice result!

[Herra Kuulapaa]

Thanks,

The sub zero sensor temperature is quite easily reached but on the other hand electronics seem to clearly increase heat. At this point I'd like to believe active cooling increases the performance by a "clear" margin

It's a bit colder today and sensor seems to meet -5°C with 1/4 power now.

[Ajohn]

There is an interesting hack post on noise that I have not really looked at closely yet.

https://landingfield.wordpress.com/2014/05/13/teaser-nikon-dslr-black-point-hack-for-astrophotography/

Some where around on the same site there is info on modifying the filtering as well.

Interesting comments about canon - nikon noise levels. Not sure they are entirely correct as companies make changes from time to time. Eg my E-M5 uses a Sony sensor. Turns out that My E-M1 uses a Panasonic one. Noise levels are similar but the E-M1 seems to have less chroma noise. I believe Nikon use Panasonic sensors from time to time as well.

Live view will heat the sensor up - it's being used all of the time. Some mirrorless cameras go to some lengths to only activate it when needed and even warn about that effect when the rear screen is in use.

John

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[Herra Kuulapaa]

That dark current mod (also a firmware for D5100) is a really good piece of code. It helps you to get the last piece of signal out of noise and I have a feeling that it really makes the difference. Of course it disables the channel scaling, that may create some balancing issues with RGB-cameras but for monochrome DSLRs it's very usefull.

That heavily tweaked heart above has been exposured with it. Here is a bit more "natural" version with more data:

1.5 hours per channel

[kalasinman]

I have the dark current firmware in my un-modded D5100. I find the improvement in dynamic range is very useful.

[frostynixon]

Herra that`s an amazing image. I wonder if CCD`s could do much better (but i doubt it).

[kalasinman]

But, it's so true what you said about passive cooling and it should be adequate.

Main idea is also to stabilize dark current for better dark frames, but I have one unmodified D5100 lying around and even cut 1mm copper element ready (it was too short for TEC but suits fine to passive cooling).

I read elsewhere that some of the heating over a series of exposures is due to battery heating. Just curious whether you have eliminated the battery with a mains supply.

[Herra Kuulapaa]

I read elsewhere that some of the heating over a series of exposures is due to battery heating. Just curious whether you have eliminated the battery with a mains supply.

Battery drain of course heats the body as well. Actually I had to test it two nights ago when my DC power supply suddenly failed. In the end it was only some frost, but I had to finish the exposure series with battery power.

I didn’t notice any temperature difference with the battery, but it doesn’t mean there is no difference. Rather it was just due to the conditions: -5C outside temperature, -10C active cooling on, so most likely cooling effect was stronger than battery heating.

During the summertime I have noticed warmer battery though, so it makes sense to use DC adapter in astrophotography. It also makes it easier not needing to worry about the charge. I’m regulating 12V->9V and use cheap ebay DC adapter.

[Coco]

Exciting stuff , cant wait to see more from this sensor, thanks for your efforts.. 

[Herra Kuulapaa]

There are more pictures in this thread:

http://stargazerslounge.com/topic/236643-nikon-d5100-monotec-narrow-bands/page-2#entry2597725

[MarsG76]

Hi,

I attempted to cool my DSLR and I'm wondering what is the ambient temperature that you're imaging at to reach and sustain -4 degrees? 

I am cooling my DSLR with two very insulated peltiers on two sides of the copper plate and can not get below 16 degrees, mind you that my ambient is 25 degrees at night, generally my 15-30 min subs are exposed at 22-24 degrees when cooled where uncooled subs are heating upto 38 degrees.... is the difference between the temperature you're reaching and i'm getting the ambient we image at?

Link to my project is here: