The glory

The glory is comparable to the cloud corona (by sun or moon). Both the glory and corona are caused by diffraction of light around droplets. The glory, however, occurs around the antisolar point, and is much easier to photograph because it is far from the sun (or moon). However, the glory is also very difficult to observe, since it is below the horizon, and you will only see it when you are in sunlight above a cloud.

A bright glory as seen from an airplane, on an altocumulus deck. Up to 3 diffraction rings can be seen.

Where to look for the glory

When flying in an airplane, this situation exists. The glory, in fact, is very commonly observed by travelers nowadays. The next time you are flying in an airplane, book yourself a window seat on the shadow-side of the aircraft; if the sun is not too high in the sky you will see the colorful glory around the point opposite the sun (where the shadow of the airplane is).

The glory may also be seen when you are on a mountain and above a cloud or fog. Such glories are very spectacular, because they are nearby, and generated by a small area of cloud with similar droplets (as opposed to a large area, which may differ in droplet composition).

Clouds which show glories well are the same clouds that show corona and iridescence well: cirrocumulus or altocumulus lacunosus, lenticular clouds, and (fresh) stratiform clouds.

Photography

Photographing the glory is easy. However, in an airplane you will be moving fast, so fast shutter speeds are recommended in order to have the clouds sharp on the photo.

You can use a lens ranging from 28-150mm, albeit that the 80-150mm lenses will show the glory best. But don't zoom in on the glory too much, since there may be higher-order colored rings which would be out of view.

At night you have a slightly higher chance to see the glory (and corona) in fog by the moon. For this you should wait for a night with no wind and clear air, during full moon; surface fog will form; and if the moon is low in the sky, you have a chance to see the glory. Do a time-exposure of the antiselenic point (where your shadow is), because maybe you don't see the glory but it will record on a time-exposure.