Wednesday, October 04, 2006

Interference arc outside of secondary 9-28-06

I was outside watching small rainshowers come and go and later on as the sun came out I got small rainbow fragments here and there. Later on while helping my mother take care of the farm animals another strong rainbow formed and this one was unusual because I counted 4 supernummery arcs inside the main bow and I could also see a very well-defined supernummery outside the secondary bow. I enhance both macro images made of the two bows. The USM of the primary shows 5 supernummeries.

3 comments:

Günther Können said...

In showers, supernumeraries of the secondary rainbow are truly rare. Do you know the solar elevation?

Michael Ellestad said...

No Gunther I don't know what the sun elevation was at the time because as soon as it faded I had to get to work helping my mother take care of the farm animals. Supernummeries outside of the secondary are rare buth I can make them easily with a garden hose spray.

Günther Können said...

Yes, Michael, but supernumeraries in a garden hose spray are easier generated than in a shower, since the drop size spectrum is peaked. In a shower however, there is a long tail in the drop spectrum toward the big sizes. This causes the supernumeraries to be smeared out. Supernumeraries in showers arise only because of the (size-dependent) flattening of the falling drops and the resulting shift of the rainbow angle toward greater distance from the sun. Because of this, their mutual spacing bears no obvious relation with the drop sizes.