# Photo Adventures with Curiosity and Learning

January 22, 2010: Sunrise Halo and More Bees, Spiders and Lotus Flowers

Morning moon - I like to catch this and compare with the sunrise (or no sunrise)

Although the sunrise was hidden by the clouds -

there was an amazing halo around the rising sun. Near the horizon are bright regions, known a sun dog - caused by the refraction and reflection of light through ice crystals. The ice crystals can be approximated by an equilateral triangle with angles of 60 degrees. With the average refractive index of light = 1.34, the refracted light bends at a 22 degree angle - thus forming the halo 22 degrees off the center of the sun. Neat physics described by the links above

Another view

The halo continued for about an hour and this was the best of the images I took (f/8, 1/2000 sec, -2 EV). Note that if you draw a line through the sun, parallel to the horizon, there are two bright areas at 22 degrees either sice of the sun's axis (projected toward the viewer). These are called dogs and reflect a more uniform orientation of the ice crystals. Since the refractive index of red is smaller than the refractive index of blue, the inner edge of the halo is red in the dog region.

The mechanism of the Sunrise Halo is described by Rod Nave at Georgia State University. Basically he says that "the familiar 22° halo around the Sun or Moon occurs because of refraction in tiny hexagonal ice crystals in the air. With the 60° apex angle of the prism formed by extending the sides of the crystal and the index of refraction of ice (n=1.31) one can calculate the angle of minium deviation to be 21.84°." Rod has given permission to use his illustrations of the physics

Here Rod illustrates all the aspects of diffracted light associated with low sun angle and ice crystals

Walking back - I passed the lotus pond. Seems the white lotus open in the morning and close in the afternoon

Another view

A sort of purple lotus

Maru and Edy joined me for the sunrise and some early morning shots of Maru. Used my new 60 mm Tamron macro. Results were nice in the sunrise light

Then off to the Nephila antipodiana web - and passed Santi and Theresa

Sina

Sina and Theresa

Nephila antipodiana Here is the female a day after mating with the male (see yesterday's photos).

The female and the residual dinner catch

A juvenile Nephila

and another image of the juvenile Nephila

From the side