Sunrise - Sunset Calculator (Ruby)

[DaveyBoy]

So I found this Sunrise - Sunset formula on-line and thought it would be interesting to put it into Ruby, so I did, and it worked (eventually)

Here it is for anyone who's interested:

Sunset Algorithm with Altitude.fsm

(2.04 KiB) Downloaded 1089 times

[RJHollins]

that is cool !

[DaveyBoy]

Yeah I thought so too. It seems very accurate when compared to on-line calculators. Not too sure about the altitude though . . . I added that myself after a little googling, hope I got it right

[PrDavid]

The calculated times for sunset/sunrise are 4 hours later than they actually are. I checked the longitude/latitude coordinates for my zip code and they are correct. Any ideas?

[DaveyBoy]

Hi PrDavid

I think it may be something to do with this line here:

# 10. convert UT value to local time zone of latitude/longitude

# localT = UT + localOffset + dst

localtr = utr + 0 + dst
localts = uts + 0 + dst

I may be wrong but I think the local offset is the difference between your time zone and 0 deg longitude. this would be 1 hour for every 15 deg. Mine is set to 0 because I'm in the UK. I'll dig out the original formula I found when I get home from work and post it up.