On Fri, 23 Oct 2020 15:40:26 +0100, Pamela
wrote:

I am interested in the duration of civil twilight each day for a given
location.

Where can I get a table listing this value for each day of the year?

Of course I will need to specify the coordinates of the location. To be clear
I mean the duration between sunset and civil dusk, not the start and end
times.

Did none of the sites that Google suggested not do what you want. What
was wrong with https://avcams.faa.gov/sunrise_sunset.php or
https://www.timeanddate.com/sun/usa/seattle or
https://www.timeanddate.com/sun/usa/seattle.

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