Tutorial:
Dynamics, many short or few long exposures ?

Content:

1. Introduction dynamics
2. Dynamic weak part of a object
3. Dynamic high signal strength
4. Line graphs and histogram
5. Long exposure low gain vs Short exposure high gain

Note:
I take no responsibility or liability for what are written here, you use the information at your own risk!

1, Introduction dynamics:

When taking astro photographs on weak objects like nebulas you want the weak parts of the nebula of course to be visible, but if you take long exposures at high ISO setting or high gain the stars will be oversaturated and loss of color information. To me it look very boring.

A CCD camera normally have 16 bit ADC, Analog Digital Converter. With that you use more of the information that is stored in the sensor after an exposure. A DSLR or CMOS camera has 10 to 14 bit ADC, that limit the signal from the sensor, with high gain it clip all higher signals even if it's stored in the sensor.

Can we do anything about that? Modern CMOS sensors have very low readout noise. Then you can divide a long exposure in many shorter exposure time. It doesn't increase the total readout noise that much as it did in old CCD sensors. With many short exposures you don't over saturate the sensor as much and then have better dynamic in the data.