-30 below ambient, means ?

[Astroboffin]

Hi all,

I have asked this question before, but I just can't find where and can't remember the answer.....lol

On a cooled camera where it says that it will cool to -30 below ambient, does that mean that if for example indoors the temp is 20 degrees, then the camera will cool to actual -10 degrees, which is a drop of 30 degrees or will it actually cool to -30 degrees C in any situation.....so in my example it will actually be dropping the camera down by 50 degrees.....

Sorry if it's a stupid question, and hope it makes sense, but the answer just escapes me

AB

[swag72]

Your first example is correct - It will cool to -30 degrees below the temperature outside, so if it's 20 degrees it will cool to -10 degrees

[Astroboffin]

Your first example is correct - It will cool to -30 degrees below the temperature outside, so if it's 20 degrees it will cool to -10 degrees

Thanks Sara, now I know...

One more thing, so if I take a set of darks at say an outside temp of 5 and set the camera at -15 so the darks will be at -10... Yes

Does that mean I can only use those darks when imaging with the camera set at -15, with an outside temp of 5 in the future...? As that would be quite limiting surely.

AB

[Zakalwe]

The camera control software will normally allow you to specify a certain temperature which it the temperature of the sensor *not a variance from ambient*. So if you set it to -15, then as long as the camera is able to reach that temperature, then it is -15.

They quote a delta-T to show it's capability....if you were using the camera in sub-tropical conditions then you may not be able to reach -15. If you are in Sweden, then -15 is easily doable.

[Astroboffin]

The camera control software will normally allow you to specify a certain temperature which it the temperature of the sensor *not a variance from ambient*. So if you set it to -15, then as long as the camera is able to reach that temperature, then it is -15.

They quote a delta-T to show it's capability....if you were using the camera in sub-tropical conditions then you may not be able to reach -15. If you are in Sweden, then -15 is easily doable.

Ahhhh, now that makes sense, so am I right in thinking that when I select a temp within the software, that is going to be the temp of the sensor, and not just the amount it is going to drop by ?

So that explains how you can take a library of darks then beforehand.

But obviously this is all dependant on the ambient temp outside as to whether tha camera cooling will reduce the sensor temp to what I have selected, so for example if I select -30 and it is 25 degrees outside then it will only get the sensor down to -5 degrees....??

Thanks very much for that explanation

AB

[Tinker1947]

I run my Sensor at -12 i have then run off 20 dark's at various lengths ,30,60,120,180,300,and 600 seconds this should cover most summer evenings...i'm not sure how the quality of the Dark's increases with further lowering of the sensor to say -20 or -25....

[swag72]

There are two different ways of cooling - The older cameras just cooled to x degrees below ambient and you had no control over the final temperature. Now they have set point cooling so you can specify what temperature you want to use which makes darks easy.

I use -15 as even in Spain I can get that all year round. Means I can use the darks for many months!!!

[Stub Mandrel]

If you are in Sweden, then -15 is easily doable.

You might need a dew heater to warm things up :-)

[Astroboffin]

I run my Sensor at -12 i have then run off 20 dark's at various lengths ,30,60,120,180,300,and 600 seconds this should cover most summer evenings...i'm not sure how the quality of the Dark's increases with further lowering of the sensor to say -20 or -25....

So in your setup for your darks to work you would not be able to image in temps above 18 degrees, if you can only cool the sensor to -30, any warmer and your darks would not match....

Hence picking a set cooling figure, in your case -12, that you can take your darks at that would work pretty much all the year round..

I understand the logic behind this now, thanks for your input, appreciate it

AB

[Zakalwe]

On 22/01/2016 at 18:04, Astroboffin said:

But obviously this is all dependant on the ambient temp outside as to whether tha camera cooling will reduce the sensor temp to what I have selected, so for example if I select -30 and it is 25 degrees outside then it will only get the sensor down to -5 degrees....??

Thanks very much for that explanation

AB

Yep, that's exactly how setpoint cooling works.  Older cameras, as Sara has said, didn't have setpoint cooling and just cooled the sensor down as much as the ambient temperatures allowed.