July 2013

Tony Martinez

                                   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 July 8th. For July, your best viewing nights will be from July 1st to the 13th, and July 26th to the 31st. The Star chart below is set for Florence, SC on July 15th at 9 pm.

wholeskychart

 

Focus:
I am not about to discuss adjusting your eyepieces, or your telescope mirror. Instead, I would like to discuss how to approach an evening of stargazing.

Now there is nothing wrong with spending a night under the stars with your telescope or binoculars and randomly scanning the night sky searching for interesting objects.  However, I find that a night under the stars is always more pleasant when you have a plan for the evening. I continually stress the challenge of locating Messier Objects. Therefore, going outside with a list of five to ten new Messier Objects that you want to locate is a great approach to amateur stargazing. Days before your night out, you should determine which Messiers will be visible, and also determine their degree of difficulty. In general, the most difficult Messiers are the galaxies. In addition, choose a night at or near the new Moon, which is always pointed out above in the introduction. Finally, seek out a good viewing night; no clouds, haze, minimal humidity, etc. The best way to determine if you have a truly clear night is to use a website called the Clear Sky Chart. The local chart is centered at Francis Marion University, and can be found at http://www.cleardarksky.com/c/FMUObSCkey.html?1 .  It is actually a weather forecast for astronomers. In a future column, I will discuss the use of the Clear Sky Chart.

After you have located as many targets as possible on your list, you can then move on to random viewing, or revisit some of your favorite night sky objects. Remember; always keep your list small and not overpowering.

This month, I would like to discuss another type of night viewing plan; the constellation plan. Pick an easily visible constellation, and spend most of your viewing time only in that constellation. Except for the northern circumpolar constellations, all constellation plans are seasonally directed. This month let’s try to “Focus” on the constellation Scorpius.

Scorpius:  First of all, Scorpius is the only zodiac constellation that is not spelled like its astrological name, in this case, Scorpio. Scorpius is also the most well-known constellation of summer. Now using your own knowledge, or using a star map, first locate your target constellation Scorpius. It will be in the south all month, and most people see as a fancy letter J lying on its side.

Scorpius and Libra horizon view

 

It is one of the constellations that actually looks like its name sake; a scorpion.

scorpius

The constellation’s brightest star is Antares, which can be seen to be a red-orange giant star and is positioned at the heart of the scorpion. Below shows the size of the star Antares compared to our Sun, and the bright star Arcturus.

591px-Redgiants.svg

There are about 15 stars that define the constellation as shown below. The star that represents the scorpion’s stinger is called Shaula. At the head of the scorpion are three stars in a row. Using present day star charts and constellation images, it is hard to envision the claws of the scorpion. That is because when the constellation was first named in ancient times by the Arabs, the constellation Libra was not as it is depicted today. The two main stars of what we call Libra today were part of the ancient scorpion. Indeed, the star Zubeneschamali in present day Libra is Arabic for the “northern claw,” and the star Zubenelgenubi is Arabic for the “southern claw.” The star names stayed, but the constellations were rewritten at a later time.

ScorpiusWithLibra

Use your binoculars and slowly follow the constellation from Antares down to Shaula. As you scan this path, you will see a high concentration of stars because Scorpius lies in the direction of the center of our Milky Way galaxy. As you move downward from Antares, stop at the second main star, zeta (ζ) Scorpii. Right above zeta Scorpii is an open cluster known as the “northern Jewel Box.” This name implies correctly that there is a southern “Jewel Box.” The southern Jewel box is found in the southern hemisphere constellation Crux, which is also known as the Southern Cross. If you would like to see Crux, and the Jewel Box, you only have to go as far south as the Yucatan peninsula of Mexico; Cancun, Cozumel, or Playa del Carmen, etc. It is visible there in the southern sky in late spring.

So what is a Jewel Box? Certain open star clusters contain various stars of sometimes various colors, which when observed under very dark skies look like jewels spilled out on a black velvet background. Below are the Northern Jewel Box on the left, and the Southern Jewel Box on the right.

Jewel Boxes

Finally, whenever you scan any constellation, search out the Messier Objects in that constellation. There are four Messier Objects in Scorpius; M4, M6, M7 and M80. All four are star clusters, and are therefore relatively easy to find, check them out and add four more Messiers to your list.

scorpius-map 2

Naked Eye Sights: The Milky Way. Scorpius. Venus near Leo’s bright star Regulus just after sunset on the 21st.

Binocular Sights (7 to 10 power): Scan the constellation Scorpius enjoying the high concentration of stars. Try to find the four Messiers in Scorpius.

Telescope Sights (60-100mm): Don’t forget Saturn shining in the southwestern sky. Check out some of the Scorpius Messier clusters under higher power.

See you next month!

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