calculate function uses hard coded "Official" rather than passed-in zenith

[grumBit]

Hi Chris,

Thank you loads for the work porting the calculations to Swift, it's been very helpful!

In testing I found the sunset times for offical, civil, etc., were all the same. In Solar.swift on line 162, I noticed the calculate function was not using the passed-in zenith and was instead always using the "Official" zenith;

   let cosH = (cos(Zenith.Official.rawValue.degreesToRadians) - (sinDec * sin(latitude.degreesToRadians))) / (cosDec * cos(latitude.degreesToRadians))

This can be corrected with the following;

   let cosH = (cos(zenith.rawValue.degreesToRadians) - (sinDec * sin(latitude.degreesToRadians))) / (cosDec * cos(latitude.degreesToRadians))

Cheers, Graham.

[ceeK]

Hi Graham!

Oops! You're completely right. I'll put a fix in for this on the train this evening :)

[grumBit]

Nice one Chris. :)

My next effort is to reverse the algorithm so I can determine the zenith for a given date, time & place. Not sure my maths is up to it though!

Cheers, Graham.

[ceeK]

Bit later than I expected, but I've just merged in the fix.

Good luck in the reversal! Feel free to send in a PR if you want to add it to Solar :)