Flats and temperature

[Carole]

I was involved in a thread on another forum where an experienced imager said that flats should be taken at same temperature as the lights.  I disputed this and asked where he got the info from and this was his reply:

Its information based on first hand experience.

Example:

Cool the sensor to about 0deg, take a bunch of flats - then measure the maximum level of a few of the flats with Maxim DL.

Now, cool it to -15, do the same again.... you will notice a difference of up to 5000 - which is a lot. The reason being is that the hot pixels contribute towards the ADU reading, and therefore cooling the camera to match your lights will give a far more accurate reading.

Just wondered what our analytic members thought about this.  I have never cooled flats. 

Carole

[MarkS]

It's complete nonsense unless the exposure time of your flats is so long that the dark current begins to be noticeable.

If so then you can take flat darks.

Mark

[Carole]

I was hoping you would say that Mark.  They were talking about the Atik383L which has to have at least 3secs to avoid shutter shadow, but I would not have said that was particularly long. 

Carole