"The most basic steps in pre-processing a raw CCD image involve
subtracting bias and dark frames and dividing by a flat field frame.
The result is a pre-processed or calibrated image. Individual dark
and flat fielded frames or calibrated images can be added or averaged
for better results. I use the "master dark technique".
This technique assumes that the rate at which dark current accumulates
in each pixel is a linear function of the temperature in such a
way that dark frames for different temperatures can be made by linearly
scaling a "master" dark frame."
Kodak sensors are widely used for ultra high resolution applications
and astrophotography. Many satellite imaging systems use Kodak sensors
and optics. Kodak sensors and technical information:
I don't think Velvia is a good choice for any long exposure work
where you're looking for color fidelity as it's not a very unforgiving
stock. If I'm doing time - lapse night filming I sometimes shoot
long exposure stills at the same time, to save me from boredom and
for possible later After Effects type use or for my own stock.
I tend to use 4x5 camera for stars, because you need the resolution
for the small stars, with a 90 or 65mm wide angle for a big chunk
of sky and use one of several of the Kodak or Fuji 100 speed stocks
and get good color.
Transparency still film is sharper and has less grain than negative,
although at 5x4 size it matters less.