In my geekier moments I like a bit of astronomy and planetary science and I follow The Planetary Society’s Emily Lakdawalla on Twitter. Recently she tweeted about a design competition for images to be used in an iPhone app about exoplanets (planets in other solar systems). I got excited about this overlap in my interests and entered. It’s difficult to know what the app developer imagines, despite reading the brief, but even though I didn’t win (it seems none of the entries were accepted) it’s a great exercise and builds experience.
I chose copyright-free images (most NASA images are this licence) of The Moon, Earth (the famous Blue Marble picture which I iWarped in GIMP) and Jupiter and made a mostly featureless Neptune directly as a vector image. I changed the bitmap images to patterns, made ellipses and set the ellipse fills to the patterns. I also made an ellipse of the same size with the fill unset and about 50% opacity. I created 8 tiled clones of the planets and then created 8 tiled clones of the ellipse ranging from red to purple (automatically adding 10% to the hue for each new clone) to go on top as a kind of photo filter. The temperature of the planet is shown by its colour. Red is hottest and purple is coldest.
This ‘photo filter’ system was probably inspired by my faint memory of the way robotic missions have taken holiday snaps of planets in the past. Science isn’t that interested in beautiful colour images per se but rather monochrome camera images filtered for particular wavelengths of light. But they can slip on a red, green and blue filter (sometimes all three are not available) and take three separate pictures which can later be combined into a colour image more like what we would take if we went there.