I know this is more of a science question but my Google-fu isn't quite answering the question to my needs and it really is game related, I swear.
So I'm whipping up a new game setting that is based sort of on the Galilean moons of Jupiter. It's four small worlds orbiting a gas giant planet. The worlds are smaller than a typical Earth-sized fantasy setting with two that are roughly the same surface area as our moon and two about twice the surface area, about the size of Mercury. So, basically, worlds similar to the Galilean moons.
Anyway, I am trying to determine how big the planet will appear in the sky over these worlds. I've done a fair amount of research and gotten lots of data on the subject, but I am failing at translating that to something simple I can relate to my players. So some help from you fine, smart folks would be much appreciated.
The unit of measurement I am using both out of game and in game is a yardstick. If the ruler is held at arm's length how big does the object appear in the sky? I checked and Earth's moon looks to be roughly 3/4 of an inch in diameter. Since my worlds all orbit their host planet at roughly the same distance as the Galilean moons, how big would Jupiter appear from the surface of each?