At left is a screenshot of the iPad application LightTrac.
LightTrac displays various information about how the sun traverses the sky in any given location, along with moonrise/moonset times.
When doing any kind of outdoor photography, it is extremely helpful to know exactly how the sun is going to track through the sky. Obviously, while in the field, you can just look up to figure this out. Having an application that models the sun’s traversal such that you have an idea of how the light will change throughout the day is tremendously useful.
On a vacation or any kind of a planned photo shoot, this application makes it easy to know what photo opportunities might be optimal in the magic light of sunrise and sunset. When visiting a city for a day tour, it can help you decide on an optimal path through a city; if you travel primarily east to west in the AM, returning in the PM, you’ll maximize time with the sun at your back illuminating what is in front of you!
Beyond photography, LightTrac has also answered a question I’ve long had about my garden plot; exactly how does the sun traverse the plot and where should I plant tall stuff to minimally shade shorter stuff (the answer is that my garden’s rows are likely to be on a diagonal to the plot in the coming years!
While there is always room for improvement — knowing where the moon is can help to plan for long exposure ghostly night shots, for example and the app “only” gives phases, moonrise and moonset — the application is intuitive, useful, and generally pleasant to use.