View Full Version : Sunrise / Sunset computation

Alpine Flyer
13th May 2002, 11:59
Dear astronomers,

I am looking for a (rather easy than very accurate) formula to determine the amount of night flight time between two points of given lat/lon.

I.e. I depart at an airport with a known lat/lon at a known time and land at an airport with a known lat/lon at at known time.

There are formulas to calculate sunset/sunrise (or ECET/BMCT) for a given lat/lon. (If anyone has something like that in an easy to use form it would be appreciated, too)

What I am looking for is a formula that does a rough calculation on how much of the flight time is spent after sunset / before sunrise.

Complications such as polar crossings on midsummer day, etc. could be excluded ;) This is mostly required for flights within Europe

Anyone able to help?

13th May 2002, 16:22
Don't think this quite what you're after but there should be sufficient tools to help:


Alpine Flyer
13th May 2002, 16:31
Thanks for the link.

I have already found plenty of online calculators but would need the actual formulas to put into a handheld program.

13th May 2002, 19:57
It looks like


has the information you need. Taken from


I've only skimmed it though, so I may have the wrong tree...

Evo - ex-astrophysicist ;)

Stan Evil
14th May 2002, 19:03
Try this:


Simple it is NOT!!!:eek: :eek: :eek:

15th May 2002, 13:31
There is an app for Palm Pilots called 'CityTime' which will give the sunrise and sunset for cities in its built-in database, which you can update with new locations. Don't know what its algorithm is, though.

17th May 2002, 04:40
There is a PC based program called Lunarphase (http://indigo.ie/~gnugent/LunarPhase/) written by Garry Nugent and available as a free download demo.

The program can print graphs for the month showing the extent of daylight and darkness, and lunar visibility (so you can know how bright the moon will be, and how long during the night it will be visible). I ended up paying the registration fee for it, as it has a wealth of information.

17th May 2002, 14:50
alpine flyer,

if you are looking for palm application, i managed to find a freeware sunrise/sunset app. you can download it at

hope this helps...


17th May 2002, 16:48
I have just the program you are looking for. I am not at home at the moment but I will check that it is freeware/shareware and if it is let you have a copy.

I will e-mail you in the next day or two.

John Eacott
18th May 2002, 06:09
Alpine Flyer,

Just a thought, but night flying is usually between Last Light and First Light, are about 20 minutes after sunset, and 20 minutes before sunrise (at least in our part of the world!).

As such, your quest for sunset/sunrise formulae would not give you your night flying time, unless your rules are different.

Airservices Australia at www.airservices.gov.au have an online computation for LL/FL which may help.

18th May 2002, 21:50
Alpine Flyer

The program is shareware. Check your e-mail.