One of my mentors, Michael Frye, turned me onto a relatively new app called PhotoPills. This app provides features and functionality far above The Photographer's Ephemeris. The user interface on PhotoPills is superb, and it includes some incredibly useful features such as 3D Augmented Reality that can be used for day and night photography, and some very useful calculators and planning tools for time lapse photography. For example, you can use Augmented Reality to see where the Milky Way will be in your composition and how it will travel across the sky throughout the night. You can use Augmented Reality to see when and where the sun will be visible through the middle of the arch you're photographing, and how it will look as you adjust your composition. Wanna see how long your star trails will be for the series of exposures you've chosen? It can do that too.There's a lot more that it can do and I'll let you read about it at their website.
I purchased it earlier today and have been playing with it for the last 3 hours and am blown away by all it can do. This is going to be a very useful tool for planning at home, in the field, and while traveling to many destinations. Right now its only available for the iPhone with a free update for the iPad version that's currently in development.
It looks like an indispensible app and something worth sharing with you.