Could be handy, need to look for an Android one too ...
https://itunes.apple.com/us/app/id596674453?goback=%2Egde_1830975_member_213799590
Description
GoldenHourM is a very accurate, brilliant and very easy to use “Golden Hour” calculation application program for smart phone/tablet that will finally make it possible for both amateur and professional photographers to take the photographs of the sky and the sun during sunset and sunrise with their true and desired “red” tone(s), which occurs when the sun is at lower elevation angles, distinctively at sunrise and sunset. As it stands today existing Golden Hour programs only calculate the time for the sun to be at those predetermined elevation angle, like 10-12° based on observations using astronomical programs. The real phenomenon is far more complex then just accurately predicting the time of a desired sun elevation angle and it requires some more effort which is handled very scientifically in the GoldenHourM Program. There are basically fairly complicated two matters in accurately predicting the Golden Hour.
The first matter is to be able to calculate the sun’s position very accurately, especially at very low elevation angles like in sun rise and sun set, any date any where on earth. So, even its simplest form Golden Hour is location, altitude and date dependent. “OEA Astronomical and Navigational Utilities” is able to offer these calculations very fast and with an incredible accuracy of 0.0003 degrees any where on earth from the South Pole to the North Pole, any date, past future or present any time and atmospheric altitude!
The second matter is to calculate the atmospheric attenuation of the solar power spectrum at any altitude, location and orientation. Sun light is not composed from a single wavelength, it has a wide spectrum and it is the function of the sun’s temperature given by the Planck radiation law. The wavelength dependency of the scattering and absorption of the sunlight in the atmosphere and the variation of the atmospheric path of the direct sun light as a function of time is the only reason for having a “red shift” in the received solar spectrum, which gives us the Golden Hour.
In the “GoldenHourM” the attenuation of the solar power in the atmosphere is calculated by the numerical solution of the Maxwell’s equations by taking the wave-length and altitude dependent absorption and Raleigh scattering into consideration for the entire solar spectrum. Planck radiation law is used to calculate the spectral power distribution of the sun light in space gives which gives the initial value of the problem. This approach provides very accurate prediction of the solar power spectrum at any sun elevation angle from sun rise to sunset for any location on earth, altitude, at any date, past, present or future.
GoldenHourM gives the solar spectrum, its peak wavelength and its “Color Temperature” as a function of time at a given location at any date for any atmospheric altitude! It is always accurate any where any time and date at any altitude for the entire solar spectrum. This methodology employed in GoldenHourM allows one to predict the color of the direct sunlight as well as the scattered light coming from any direction at for any date and time and customize the reddish tone that you desire in your perfectly professional photo!
There is also “Indirect Golden Hour” which can happen if there is an obstruction of the direct sun light at lower sun elevation angles like hill or a mountain between the photographer and the sun during sun set and sun rise or there is a need to customize the color of the scattered light from the clouds. GoldenHourM calculates this far more complicated phenomenon by using additional advanced mapping functions and unique GPS based ranging capabilities. Track the sun and Golden Hour any where at any date by using advanced mapping capability provided for 39 different Languages at a fraction of the cost of our PC and work station programs for professional organizations for great Golden Hour photography!
(Continued use of GPS running in the background can dramatically decrease battery life)
