Sunrise/sunset duration

[izubiaurre]

Hi,

I have a doubt about the duration of the sunrise/sunset.

If sunrise is defined as a moment, is the moment when the sun is -0.8333º below horizon (upper limb appears on the horizon). But if we take as a duration, will be from this point to when lower limb touches the horizon? Which could be the sun's elevation at this moment? +0.8333º ? Or this value is related to other calculations?

 

Thanks in advance

[andrew s]

It depends very much on atmospheric refraction. This means the details will depend on just how much of the atmosphere you are looking through which will depend on where you are and where the Sun is during its annual cycle.  When you see the Sun set it is already well below the horizon and would not be visible without our atmosphere. 

Regards Andrew

[izubiaurre]

Ok, but coul be taken the range between sun's upper limb touching the horizon and the bottom touching the horizon as sunrise?

[rockystar]

even then there is still light from the sun,  hence twilight - so could the duration of sunset be defined as the point when the amount of sunlight starts to reduce until it is zero? 

[izubiaurre]

On 18/9/2017 at 21:29, rockystar said:

even then there is still light from the sun,  hence twilight - so could the duration of sunset be defined as the point when the amount of sunlight starts to reduce until it is zero? 

If I'm not wrong, the amount of sunlight is never equal to zero, even in the darkest of the night, there's a slight light in the sky coming across the atmosphere. 

The end of twilight is set by the elevation of the sun, that is -18º o 18º below horizon. Then, we have other sun's moments that are very apreciatted by photographers and film makers... Golden hour and blue hour.

Golden hour is more or less from 6º to -4º. 

Blue hour from -4º to -6º.

Twilight -6º to -18º.

And belowe is night.

 

So, I want something like for the duration or elevation range for sunrise/sunset.

[furrysocks2]

Wikipedia says:

Quote

Astronomically, sunrise occurs for only an instant: the moment at which the upper limb of the Sun appears tangent to the horizon.

http://aa.usno.navy.mil/faq/docs/RST_defs.php

 

[izubiaurre]

Thank you as always furrysocks2 for your response.