Fig (1)
Glowing Beauties
Spectacular iridescent clouds over Cairo, Egypt
Date: 10 March 2007 12:51 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

On the morning of Saturday, 10 March 2007, there were spectacular patterns of middle clouds in the sky of Cairo, Egypt. The magnificent display lasted over 7 hours. Mr. Aymen Ibrahem, Senior Astronomy Specialist, recorded these patterns, and imaged the wonderful optical atmospheric phenomena that were produced by these clouds.

Middle clouds appear at heights between approximately 2,000 m to 6,000 m. They are composed mostly of water droplets, but when the weather is cold enough, they may contain ice crystals. Optical atmospheric phenomena related to these clouds include coronae and iridescence.

Coronae are observed when thin, partly transparent clouds veil the Sun or the Moon. They shine as colorful rings or patches around the Sun or the Moon.

Iridescence, or irisation, occurs when thin clouds with equally-sized droplets veil or pass near the Sun. They are similar to the coronae in color, and may be regarded as corona fragments. The terms irisation and iridescence are derived from Iris, the Greek goddess of the rainbow.

Caution: Never observe the Sun directly with your eyes. When observing coronae, iridescence or any other solar phenomenon, the observer's eyes must be adequately protected. Beginners should observe the Sun under the supervision of an astronomy specialist.

"I began observation at about 8:00 EET, from my home," said Ibrahem. "Properly protecting my eyes, I imaged pastel-hued iridescence and a dazzling Sun corona. When the clouds drifted away from the Sun, the corona disappeared."

Fig (2)
Sun Corona over Cairo
Date: 10 March 2007 9:14 EET
The photographer blocked the Sun disc with his own hand.
Photo by Aymen Ibrahem, Senior Astronomy Specialist

After observing the Sun corona and the iridescent clouds, Ibrahem made a trip to the Giza Zoo, to practice his hobby of wildlife photography. The object was to photograph the cattle egrets, wild birds that nest in large numbers in the trees of the zoo and nearby locations. He also continued observation of the memorable cloud patterns that continued to stream in the sky.

Fig (3)
Splendid cloud patterns and Cattle Egrets over the Giza Zoo
Date: 10 March 2007 10:12 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

"A week earlier, also in the Giza Zoo, I photographed wild birds that nest in the zoo's trees, or nearby locations, including parakeets, parrots, cattle egrets, falcons, wagtails and pigeons," said Ibrahem. "It was my first time to photograph brooding egrets. Hence, I expected to photograph their chicks within a few weeks."

From about 10:00 EET to 13:30 EET, Ibrahem recorded several Sun coronae and iridescence phenomena. At about 12:51 EET, however, there were wonderful iridescent clouds, glowing in bright, vivid colors. Ibrahem took a series of images showing their development.

 
"They were the most beautiful iridescent clouds I have ever observed. It was a lifetime experience, nearly as spectacular as observing a total solar eclipse."

Shortly later, he imaged another Sun corona, and softly-hued iridescent clouds. Ibrahem also realized his target of photographing egret hatchlings. More images are presented in the picture gallery below.

Picture Gallery

Fig (4)
Awesome iridescence over the Giza Zoo
Date: 10 March 2007 12:51 EET
As the clouds were streaming in the sky, the iridescence evolved, as revealed in the following images.
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (5)
Date: 10 March 2007 12:51 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (6)
Date: 10 March 2007 12:51 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (7)
Date: 10 March 2007 12:51 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (8)
Date: 10 March 2007 12:51 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (9)
Date: 10 March 2007 12:52 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (10)
Date: 10 March 2007 12:52 EET
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (11)
Egret Hatchlings
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (12)
Egret Chicks Close-up
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Fig (13)
Egret Chicks Close-up 2
Photo by Aymen Ibrahem, Senior Astronomy Specialist

Further reading
Calm aster the storm
http://www.bibalex.org/eclipse2006/News_Details.aspx?id=199

Aymen Mohamed Ibrahem
Senior Astronomy Specialist