Wandering through the realms of the cosmos, pondering its huge vastness

Posts tagged “atmospheric optics

Skywatching Treat on Christmas Day

On my way home after attending tonight’s Christmas Day Mass, I saw a faint ring or halo around the Moon. Lunar halos often result when moonlight enters randomly- oriented hexagonal ice crystals in wispy cirrus clouds. Refraction of light produces a 22 degree ring or halo around the Moon. In order for a halo to appear, the Moon must be at least 22 degrees above the horizon. Interestingly, Jupiter was also positioned inside the 22 degree halo on this night near the waxing gibbous moon.

Lunar halos usually indicate that a bad weather is on it’s way. In the Philippines, a new tropical depression is expected to bring heavy rains across central part of the country in the next few days.

Image taken using hand-held Canon Powershot SX40 HS.

Merry Christmas, folks!



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Iridescent Cloud from Above

Sometimes we can see several colors of red, blue or green in edge of cirrus or altocumulus in higher sky. These colors appeared when water droplets of nearly uniform size in clouds diffract sunlight. This relatively rare phenomenon is known as Cloud Iridescence.

The mechanism of cloud iridescence is quite same with the case of corona light around the sun or moon.

Here are photos an iridescent cloud that my friend, Andre Obidos took  while on board an airplane going to Cebu. He shared them to me when he came back to Manila. Thanks, Dre. 🙂

To me, it looks like a head of a colorful bird such as a Lorikeet. It’s beautiful, isn’t it?

Nature is really full of God’s wonderful surprises.

Pink Contrail and the Crescent Moon

On the walk from our house to the street one afternoon,  a nice sight in the western sky caught my eyes — the  27% illuminated waxing crescent Moon and a pink-colored sunlit contrail against a blue-violet sky. This contrast of colors looked just fascinating. 🙂

Fortunately, I brought my Kodak digital camera with me so I was able to take a picture of it. The image turned out to be a bit blurry though without using a sturdy tripod.

Notice that while both the Moon and the cloud were illuminated by the same Sun, the cloud was pink and the Moon was so white. The answer lies in the fact that the atmosphere absorbs and scatters the shorter (blue) wavelengths of light, while allowing the longer (red) wavelengths through. The low angle afternoon sunlight arriving at the cloud (contrail) had traveled through significantly more atmosphere than the more “pure” sunlight reflected by the Moon.

A Moonbow!

Have you seen a rainbow at night?

Well to be honest, I have never seen one with my own eyes.

But luckily, a persistent astrophotographer from Kamuela, Hawaii has recorded this spectacular example long after dark:

Credit: Ethan Tweedie of Kamuela, Hawaii

In this picture, the bright moon played the role of sun, illuminating nightime raindrops falling through the damp Hawaiian air.

This long exposure image also revealed something even more rare: a secondary moonbow. It’s the faint ‘bow arciing above the brighter primary.

Primary rainbows are caused by single reflections inside raindrops; secondary bows are caused by double reflections.

It was a night to remember, indeed. 🙂

Image was originally featured in http://spaceweather.com/

Sunset by the Beach and Moon at Dusk

While spending our short vacation in the lovely island of Panglao in Bohol, we took the chance to reunite ourselves with the beauty and comforting embrace of nature. This island that is very famous for its pristine beach — clear, turquoise waters and dazzling white-sand — is really a perfect tropical sanctuary of natural beauty. 😀

As we were so excited to watch the sunset, we immediately headed toward the beach after our day-long tour on the other part of the island. Luckily, we got there just in time to witness this magnificent scene.

Notice the anvil-shaped cloud near the setting sun in the close-up photos above. Anvil clouds are the icy upper portions of cumulonimbus thunderstorm clouds that are caused by a rising of air in the lower portions of the atmosphere. They usually indicate a coming rain. Nevertheless, only a slight drizzle came later in the evening.

A few minutes after sunset, the thin crescent moon became visible as it slowly descended towards the western horizon following the Sun.

These sky displays never fail to make me smile and I was truly glad that I was given the chance to witness all of these during our vacation. God is really so great.

Special thanks to Andre Obidos for letting me use his sunset photos.

I will definitely miss this place a lot. 🙂

Supernumerary Rainbow over Cebu City, Philippines

Last February 5, I and some friends flew to Cebu City, the ‘Queen City of the South’ to tour around and explore some of its famous landmarks. As we were walking towards the harbor during the late afternoon, we felt a slight drizzle rain down our heads.

One of us thought that these conditions were perfect to see a rainbow. When white light from the Sun hits the raindrops at a certain angle, rainbow formation is possible. The angle is important as it effect the direct the light travels after it hits the raindrops and that determines whether or not we will see a rainbow. It is best if the sun is fairly low in the sky such as dawn or late afternoon just like during that time. To view a rainbow, your back must be to the sun as you look at an approximately 40 degree angle above the ground into a region of the atmosphere with suspended droplets of water. By knowing this, one of us found the brightly colored arc which formed above us. At first it was faint, until it become more and more visible. A secondary rainbow has also formed –  seen above and outside the primary arc, and has the order of its colors reversed (red faces inward toward the other rainbow, in both rainbows).

It was really a splendid sight! 😀

As I looked more closely, I noticed something unusual yet strangely familiar phenomenon. On the inner (blue) side of the primary bow, there were also several slightly detached and pastel colored bands that do not fit the usual pattern. It was then that I realized that we were actually looking at a supernumerary rainbow!

Notice the closely spaced greenish purple arcs on the inner (blue) side of the primary bow. (see inset picture)

A supernumerary rainbow—also known as a stacker rainbow—is an infrequent phenomenon, consisting of several faint rainbows on the inner side of the primary rainbow, and very rarely also outside the secondary rainbow.

The primary rainbow results from a single internal reflection of refracted light inside a raindrop, and the secondary rainbow results from a double internal reflection. But the additional rainbows are not explainable by geometric optics, and hence had been termed “supernumerary”.

Supernumerary rainbows result from interference of light which undergoes single internal reflection but travels along different paths inside a raindrop.

Seeing this rainbow is a gift from above.  It seemed like it has served as a lucky sign that we would have a nice weather throughout our whole trip; and indeed it happened. 😀

“I have set my rainbow in the clouds, and it will be the sign of a covenant between me and the earth.” (Genesis 9:13,15)