A project I started back in 2010, when the first iPad came out. Cor Leonis is an astronomy app for iOS devices, accurately displaying constellations, as well as sun, planets, and the moon, given an observer’s position and time.

Here are some impressions of the iPhone UI:

My primary motivation was curiosity: How does this all work? For instance,

• getting and parsing star catalog data
• calculating the sky view for a given time and position on Earth
• determining the phases of the moon
• computing planet positions

I still remember the excitement, when the actual sky outside was matching my app screen!

Another large part of the project consisted of compiling descriptions, legends, historical bits around the 88 constellations. I learned a lot about them this way!

The app was available in the Apple Store for a few years. I eventually took it down, because the maintenance effort for keeping up with iOS versions was getting too high. I did incorporate most of the algorithms into the successor Virtual Reality app, Pocket Observatory.