The magic hour is the time when the sun is between 6 degrees above and below the horizon. This is know as civil twilight. It varies in duration based on your location and time of the year.
If there are mountains the sun may disappear earlier so you will loose the 'golden' part of it
early. In some places they call it 'golden hour' (Canada) because it is golden before the sun
sets, in others the call it 'blue hour' (France) because it gets deep blue after the sun sets...
The main point is that contrast between subject and sky is quite low during that time, so you
can get photos with good detail in both.
- Itai
Neoluminance | Fine Art Photography by Itai Danan