ImageCalibration Dark Optimization: How does this minimize noise?

[astropixel]

The 120 second dark seems to be dominated by bias and fixed pattern noise, compared to the bias frame above. Fixed pattern noise is significant in the shorter dark frames and BasicCCDParameters reports a negative value between the bias and dark shown here.

Additional noise - the sharp horizontal lines - is generated by the cooling system electronics. The Logic Level MOSFET is switching in response to PWM. I have suppressed most of the interference, but really need to redesign that part of the electronics.

Flat on the right.

EDIT: Fixed pattern noise seems to be dominant in the shorter 0C dark. I am led to understand that read noise is also an issue. Fixed pattern noise is an issue with the 1000D.

[pfile]

your note about the switching noise is really interesting. someone on the DSLRAstro Yahoo group said that he had horizontal banding noise until he disconnected the laptop that was driving the camera from the mains. i wonder if he was also running the camera with an AC adapter. of course it can be possible to couple noise into the camera from the USB connector.

how about putting a ferrite bead around the power supply wires for the peltier?

[astropixel]

A ferrite rod of the right size will work, I have a circuit in mind, but enthusiasm is waning. I'm using a capacitor across the FET gate and source at the moment, crude, but it works - adequately. PI rejects the lines in any case. Switch mode supplies cause interference just plugged into the mains without switching on the power. The camera chassis must be tied to GND. Then deal with the power supply on noise.

[ruediger]

Here is try #3. I have not had time to read the development threads - my apologies - squeezing in the time out of interest.

Looks good now! Compare e.g. to the results from http://www.fredmi.fr/en/rebel-xs/2-le-canon-eos-1000d.html. Thanks again for testing! I try to take care of the reported usage problems and also have lots of ideas for extending functionality.

Rüdiger