Geek Answers Handbook

How to calculate dawn / dusk time

I am currently using this code to calculate sunrise / sunset times. (To be more precise, I am looking for times of civil dawns / civil twilight, which are defined as the time when the sun is between 0 ° and -6 °). As a next step, I would like to calculate the start of dawn and the end time of twilight. I believe the calculations should be very similar.

My idea is that if I want to calculate the start of dawn (dusk end time) for a place, I just calculate the sunrise (sunset) time for a place 6 ° further east (west).

Can someone confirm this assumption, or am I not mistaken?

Thanks for answers!

- Ry

EDIT: The thought of this is a bit bigger and came to the conclusion that my assumption is wrong. A 6 ° east longitude movement is incorrect, a 6 ° movement orthogonal to light / shadow will be correct. (This becomes obvious if you imagine that the Earth’s axis is not tilted 23.xx °, but 90 ° - moving east will not change anything).

+5
source share
4 answers

, , (90.833) calcHourAngle*. / , 90.833 " ". , , 96. , , ?

+2

, , . , , - ( ) ( ) - . , , ~ 16 (: ).

, , . 24 24 . "" "", , .

0
source

This does not work. An easy way to prove this to yourself is that at the poles the height of the sun does not change as your body rotates, so going east or west by 6 degrees will not affect your time.

If you are closer to the equator, this calculation is likely to be more accurate, but I don't think it is ever perfect.

0
source

More articles:


All Articles