Senior Member.
This website explains many of the interesting things seen in the sky.

Light playing on water drops, dust or ice crystals in the atmosphere produces a host of visual spectacles - rainbows, halos, glories, coronas and many more. Some can be seen almost every day or so, some are once in a lifetime sights. Find out where to see them and how they are formed. Then seek and enjoy them outdoors.


Senior Member.
I used an early version of their wonderful HaloSim software in my BSc nearly 10 years ago now- the same one they use on the site for simulated examples.
I can't recommend downloading it highly enough, as it's fun even just to play with conditions and trace ray paths to understand how these things all fit together. It also has the exact conditions (if i remember rightly) pre-programmed to create a host of rare halos and arcs. Really great fun, admittedly mostly for optical phenomena geeks. I think it might even have the Tricker arc...