Hi,
This page contains links to technical articles I have written:
Long Exposure Sensor Tests.
Not all sensors are made equal or continue to perform as expected when pushed.
Long Exposure Noise Reduction (In Camera).
A brief run through on how the in camera NR works.
HDR Imaging
How to shoot for HDR and post process to HDRI.
Long Exposures
How to shoot long exposures, required equipment and calculating exposure.