Sunrise/sunset trivia

[RWood]

At what latitudes could you be if there was a (roughly) 3-month period during which the sunrise time varies by no more than about 2 minutes? Or the same question for sunset?

Certainly not on the equator, where both times vary by about 31 minutes over the course of the year, thanks to the equation of time.

The following can be verified (for 2008) at

http://aa.usno.navy.mil/data/docs/RS_OneYear.php ,

using Form B with universal time.

at 8.15 North, sunset is at 1809-1811 from 7 Feb to 15 May (99 days).
at 10.30 North, sunrise is at 0549-0551 from 29 July to 2 Nov (95 days).

at 8.45 South, sunrise is at 0602-0604 from 10 Feb to 12 May (93 days).
at 10.45 South, sunset is at 1755-1757 from 24 Jul to 27 Oct (96 days).

Of course, since the times are only given to 1-minute accuracy, the numbers involved are only approximate.

[ATO2]

Good to be reminded of that. So many people think the Equator hardly varies but it does!

[TokWW]

Interesting info and utility. and a lot has to do with the tilt on the axis...

[RWood]

Yes, the 23.5deg tilt is the bigger contributor to the equation of time.

I quite like the idea that at those latitudes there are times of year where you could (more or less) have your watch accurate to within a minute or so just by watching the sunrise or sunset as applicable, having of course got yourself a flat horizon!

[ATO2]

Originally Posted by RWood

Yes, the 23.5deg tilt is the bigger contributor to the equation of time.

I quite like the idea that at those latitudes there are times of year where you could (more or less) have your watch accurate to within a minute or so just by watching the sunrise or sunset as applicable, having of course got yourself a flat horizon!

Yes, nice warm latitudes....LOL