Thanks for posting the link to info on Sundogs, Philip
There are so many atmospheric phenomena, rainbows being the most obvious. Halos, various arcs, belt of Venus (visible twice a day everyday! And so few people are aware that it is Earth's shadow at play here too! The single largest shadow on Earth is Earth's own shadow being projected onto the atmosphere at sunrise and sunset), green flash, and many others. You will find an extensive list here:
https://en.m.wikipedia.org/wiki/Opti...ical_phenomena
Alex.