Section 6 of 6
Observing
Why it is grey, and how to see more of it. The eye is the instrument that limits all of this. These are the things that change what it can register.
Why almost everything is grey
The eye's low-light system carries no colour. Photographs are not lying, but they are not what you will see.
Dark adaptation
It takes far longer than people allow, and one white light undoes it.
Averted vision
Looking slightly away to see something faint, and why that works.
Seeing and transparency
A steady sky and a clear sky are different things and rarely arrive together.
How dark is dark
Naming sky brightness, and what each step actually costs you.