2
$\begingroup$

If I do a quick Google search for amsterdam sunrise, I immediately get the time back: 6:42 AM.

How is this time calculated?

(I mean how it is really calculated, not how Google get it, with is probably from a table. Of course I mean sunrises and sunsets in the future, not from the past. $:)$)

Improve this question
$\endgroup$
5
  • 2
    $\begingroup$ Do you know about the sunrise equation? Scroll down to the bottom. $\endgroup$
    – HDE 226868 ♦
    Commented Aug 25, 2016 at 20:02
  • $\begingroup$ Thanks, no. From what I read I can calculate $\omega_o = \text{acos}{(-\tan(\phi)\tan(\delta))}$ with in my case $\phi = 50^{\circ}$. How do I get the value of $\delta$ and how do I convert $\omega_o$ to HH:MM (hours and minutes)? Thanks in advance. $\endgroup$
    – Kevin
    Commented Aug 25, 2016 at 20:11
  • 1
    $\begingroup$ For $\delta$, see here. You just need to find the solar declination of the day. $\omega_o$ is a spatial coordinate, not a length of time. For the date, you need to do a bunch of intermediate calculations, then find the Julian date. $\endgroup$
    – HDE 226868 ♦
    Commented Aug 25, 2016 at 20:17
  • $\begingroup$ You can use the CSPICE libraries to calculate it exactly, and USNO publishes it for a wide variety of locations, but I think you're asking: what simple equation does this so that websites can use it (or use JavaScript) without having to do super-precise calculations? $\endgroup$
    – user21
    Commented Sep 1, 2016 at 17:16
  • $\begingroup$ Yes, that's what I meant to ask. 🙂 $\endgroup$
    – Kevin
    Commented Sep 2, 2016 at 11:56

0

Reset to default

You must log in to answer this question.

Browse other questions tagged .