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

Posts tagged “atmospheric phenomena

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. :D

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! :D

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. :D

“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)


Lunar Halo and Jupiter

In hope of observing the Orionids Meteor Shower, I and some UP Astrosoc friends planned to go to the south to avoid the unfavorable weather in Manila. Unfortunately, we were not able to pursue the plan due to the heavy rain. Instead, we went to Naic, Cavite, a town just a few kilometers outside Manila, a day after super typhoon Megi left the country to try our luck.

We arrived at the local beach resort and started setting up our things including our tent at around 11:00 PM. The sky was totally overcast, but the waning gibbous moon and a star, which I know was the planet Jupiter, were visible then.

After a few minutes of observing the two, we noticed a faint but full 22 degree lunar halo circling the moon. Jupiter was just within the circle. We even got more amazed as the halo became clearer when the moon reached the zenith. One of us took a shot of this stunning view using her Canon 400D Digital SLR camera.

Lunar halos are caused by sunlight being refracted by cirro-stratus clouds.  Cirro-stratus clouds are thin clouds, very high in the atmosphere, and are composed of ice crystals. The shape of the ice crystals results in a focusing of the light into a ring. They bend light at a 22 degree angle, which creates a solar halo or lunar halo that is 44 degrees in diameter.

Since the ice crystals typically have the same shape, namely a hexagonal shape, the Moon ring is almost always the same size. Less typical are the halos that may be produced by different angles in the crystals. They can create halos with an angle of 46 degrees.

 

Image courtesy of  Bea Banzuela.  Photo details: 18mm f/10 ISO-800 at 30 sec exposure. Click image to see larger version.

The sky remained overcast during the rest of the evening until twilight and so we were not able to see even a single fireball.

Nevertheless the attempt was worth a try, thanks to that wonderful halo which left us amazed and happy. :D

 

Image courtesy of UP AstroSoc member Bea Banzuela.Taken using Canon 400D 18mm f/10 ISO-800 at 30 sec exposure 

 


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