September 2010

Tony Martinez

Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on September 8th. For September, your best viewing nights will be from September 1st through September 13th. The Star chart below is set for Florence, SC on September 15th at 9 pm.

Perseids Meteor Shower:

My personal observations of the August meteor shower between 1 and 2 am had a count of about 12 meteors per hour; not really enough to be called a shower. A reader of this column, who observed at a darker sky site near Charleston, reported 25 to 30 per hour between midnight and 1 am.

Jupiter:

Jupiter returns as the best planetary target for your telescopes. The two best planets for small telescope observation are Saturn and Jupiter. Saturn is usually the most impressive target because of its beautiful ring system, and Jupiter is known for its atmospheric bands, red spot (not very red), its four major moons, and its large disk size. However, for the last year, and continuing for several more months, Saturn’s rings have been tipped toward the Earth, therefore making them less impressive.

This month Jupiter moves into opposition with the Earth on September 21st. Opposition occurs when the planet is directly opposite the Sun as seen from Earth. (Lunar opposition is called a full Moon). At opposition, the planet is also visible the entire night. In addition to being at opposition, due to variations in orbits, some years any given planet may be closer or farther away during opposition. If you are younger than 47 years old, this month is the brightest and largest you will see Jupiter since you were born. The last time that Jupiter was this close was October 1963.

As you know, Jupiter is the largest planet in our solar system. Although it can be at times over 500 million miles from Earth (460 million this month), due to its size, it is always a good telescopic target. Below is the size of Jupiter compared to our Earth.

Observing Jupiter: Jupiter is the only planet that can be enjoyed using simple seven or ten power binoculars. With low power binoculars, Jupiter will not be seen as a disk, but its four major moons, Ganymede, Callisto, Europa and Io, known as the Galilean moons, will be readily visible. These moons move quickly around the planet, therefore each night they will be seen in different positions. In addition, some nights they will disappear as they move in front or in back of the planet. So on any given night, you usually see from one to four moons. If you would like to try viewing the Galilean moons through low power binoculars, try it on the night of September 24th. Begin observing between 8 and 9 pm; Jupiter will be low in the southeastern sky. You should see the planet, and three of its moons lined up on the left side. The “missing moon is Io. As the night progresses, Io will swing out to the right side of the planet. Check every hour or so until Io becomes visible. Depending on the quality of your binoculars, and more importantly the clarity of the sky, you should see Io appear between 11 pm and 2 am.

If you use large binoculars, 25 X 100 mm, on a clear night you will also be able to see the cloud bands on Jupiter. The image below approximates what I can see through my large binoculars. Note that the cloud bands are just barely visible at 25 power.

Most telescopes will allow you to easily see the cloud bands of the planet Jupiter. However, there are many factors that affect telescopic viewing. Besides the obvious cloudy or hazy nights, atmospheric moisture and or turbulence are also a problem. On many occasions, your eyes will see a clear night with many stars visible, but atmospheric conditions not visible to the naked eye will affect clear viewing through your telescope. Therefore, if you have a decent refracting or reflecting telescope and are unable to see the bands on Jupiter, keep trying on other nights. The most likely cause is the atmosphere, and not your telescope. However, there is a way to determine if it is truly a good night for superior viewing; the Clear Sky Clock website http://www.cleardarksky.com/c/FMUObSCkey.html?1. This website offers the best viewing condition information for amateur astronomers. If you visit this site, it can be somewhat confusing at first. I will feature the Clear Sky Clock next month and describe all of its capabilities.

Now assuming you are able to view Jupiter this month on a clear night, you should note that something has changed on Jupiter. Jupiter is known to possess two obvious dark bands, know as the northern and southern equatorial belts. However, if you view Jupiter this month, you will notice that the southern belt is missing. It recently disappeared, and is expected to return in the future, but no one knows when it may return. This phenomenon has occurred before, and no one knows the cause. If you look above at the size of Jupiter versus the Earth, you can imagine that this is no “small” event. Below is an image of Jupiter last year compared to this spring.

All in all, this month “belongs” to Jupiter, so go out and enjoy the view.

Naked Eye Sights: Jupiter will be the brightest “star like object” this month.

Binocular Sights (7 to 10 power): Jupiter and its moons. Try to observe the Io movement on September 24th.

Telescope Sights (60-100mm): Jupiter and its moons. Take note of the “missing southern band.”

See you next month!

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