Tehachapi sky watch
Tehachapi sky watch
By: Dale Hawkins
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Posted by editor Tue Oct 3, 2006 16:31:14 PDT
Viewed 384 times
0 responses 0 comments Sunrise, Sunset
The smoke from the Los Padres National Forest fire has played havoc with the clarity of our night sky. However, it has contributed to some beautiful sunsets of late. While the fire is certainly a tragedy for some and a hardship for many, there is always at least a small upside to any downside. Do you remember the outrageous sunsets in the weeks after Mount Pinatubo erupted in 1991 in the Philippines?
As a sky watcher and amateur philosopher, I've spent many an evening and morning watching the sun rise and set. Many songs and poems have made references to them. For me, the rising and setting of the sun holds several fascinations and amazing beauty.
When the sun is overhead, it shines straight down through our atmosphere, inundating us with photons that blind the eye and burns the skin. To get above half of our atmosphere you need go less than three miles straight up (18,000 ft. above sea level). When the sun is low on the horizon, however, we're looking through much more atmosphere, with the half-way point being more like thirty miles. That much atmosphere, especially with all of the dust and pollution we're looking through, acts as a great filter, cutting out the higher-energy wavelengths, such as ultraviolet and blue, leaving us a comfortable red-orange sun.
Sunsets tend to be more colorful than sunrises because there is more dust and pollution in the evening sky, with much of it settling out before dawn. This is doubly so of late as the fire rages during the daytime, spewing huge amounts of pollution into the sky. Overnight it cools off a bit while the day's smoke settles and disburses.
It's important to remember that sunsets are at their most colorful about ten minutes after the sun has set below the horizon. It then shines up on the high clouds overhead. (Note that I said, “the horizon,” not just the tops of the hills. I've started including actual sunrise and set times at the bottom of this column, since we all have hills on our horizon.) So don't rush indoors just because the sun is no longer in view. The best may be yet to come.
Another effect of the sun being close to the horizon is the illusion of magnification. When high in the sky, the sun appears smaller than at the horizon. Conventional wisdom suggests that the image is magnified by the atmosphere at low angles. But if you take photographs of the sun at high and low angles, they measure the same angular size. The illusion is purely human. When the sun is high, we have no nearby references for judging its size. When near the horizon, we do, which causes it to appear larger in our minds-eye.
Another fascination is watching the sun move as it rises or sets. Astronomical bodies tend to move very slowly by our perception, with most never moving perceptibly at all against the background in our entire lifetime. It's really this relative movement that makes planets so fascinating to humankind. Indeed, “planet” is Greek for “wanderer.” The rotation of our planet is one phenomenon that we can actually see in real time, albeit still quite slowly by our standards. We can watch the stars and the moon rise and set just like the sun. But the sun is a particularly dazzling object to watch as it sets, for it becomes easier to look at, changes the sky to more comfortable and peaceful colors, and ushers in the “dark sacred night” in splendid style.
Manned Space Watch
A Russian Soyuz spacecraft has delivered two new crewmembers to the International Space Station, as well as another space tourist, American Anousheh Ansari, the first woman space tourist. The next shuttle flight is scheduled for December when Discovery will deliver another truss segment and the SpaceHab module to the station.
Night Sky Watch
The moon dominates the evening sky, setting later each day, and growing brighter until the full moon on Friday, Oct. 6.
The moon will pass through the Pleiades Star Cluster on the evening of Oct. 9. A pair of binoculars will make it easy to see stars popping into view as the dark limb of the moon slips past them. To find the Pleiades that night, just look for the moon rising in the northeast.
Jupiter is still bright in the southwestern sky shortly after sunset this week, but is sinking rapidly as we leave it behind the sun.
Saturn is getting easier to find in the eastern sky before dawn as it gets higher in the sky each day. By the end of October, Saturn will rise shortly after midnight.
Keep your eyes on the sky!
Sunrise/Sunset (PDT)
6:51 a.m./6:33 p.m.
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