31 October 2014

Amazing Sunset and Sunrise Colors

Every sunrise and sunset provides a wide range of visual effects, ranging from the elongation of the disk of the Sun as it hugs the horizon, to the amazing range of colors you see in the minutes before and after the Sun’s passage through the horizon. One of my favorite effects is the curious coloration of the opposite horizon from the sunrise or sunset where one sees a colorful and rapidly changing band of sky called the Belt of Venus.

Belt of Venus at 35,000 Feet
Despite the name, the effect does not have anything to do with Venus the planet. Rather, the effect is due entirely to the shadow cast by the Earth into space, and our perception of that shadow as we observe the horizon from our vantage point along the Earth’s terminator. As we gradually rotate out of the darkness of night (at sunrise) or into the darkness (at sunset), we have a short-term view into the shadow of Earth which occupies the opposite horizon from the Sun. The colors are quite vivid with dark blue low along the horizon, and the refracted colors of the sunrise or sunset above that, creating a layered effect of blue and pink.

Belt of Venus on SF Bay
The images to the left and right show two interesting views I had of the Belt of Venus over the past many months. The first one was taken from 35,000 feet above the United States where I had the very unique vantage point of looking sideways into the sunset belt from high altitude rather than seeing it from sea level. I still cannot figure out why there is a white glow below the belt itself. The second image was taken from the Exploratorium in San Francisco, looking east after sunset toward Treasure Island and the Bay Bridge. The colors and pattern on the horizon were to be expected, but the rays of dark and light blue extending up into the sky were not. Here in this situation, I still cannot figure out the atmospheric phenomenon that would cause such an unusual ray of dark blue to extend upward into the sky. But in both cases the interplay of color and light was indeed remarkable and although pictures from an iPhone camera cannot do justice to the magnificence of the real thing, it’s something I felt compelled to document and write about.

So next time you are watching an amazing sunrise or sunset, be sure to turn around and take in the drama on the other horizon, or you will have missed out on some of the most beautiful parts of the sky.

04 October 2014

The Next Blood Moon: October 8, 2014

Total Lunar Eclipse of October 8th
We're in for the second of four total lunar eclipses in 2014-2015. Next week the Full Moon slips into the shadow of the Earth and reveals itself as a 'blood moon' in the early morning sky of Wednesday October 8th. You'll need to be up in the wee hours of the night, as the eclipse reaches total phase at 3:25 am pacific time, where it will remain in total eclipse for an hour. Given our good weather in San Francisco, this should be nicely on display and the view from the west coast should be nice, if you can get out to the beach. The Moon itself will not be a 'super moon' but will be larger than most Full Moons, so it should be an awesome sight.

You can find more details on the Sky & Telescope website. You'll need clear skies and a good view of the sky to the southwest. It should be a dramatic blood-red color, as the Moon will move deep into the umbral shadow of the Earth.

This infographic from Guy-AndrĂ© Pierre-Nicolas of astroshop.eu is an excellent resource that illustrates beautifully many facets of a lunar eclipse.

Image courtesy of Sky & Telescope.