October 2012

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 October 15th. For October, your best viewing nights will be from October 6th to the 18th. The Star chart below is set for Florence, SC on October 15th at 10 pm.


Binocular Astronomy:

Although I always include a section called binocular sights at the end of my column, this month I will feature that section. In previous columns I have explained that the best approach for learning astronomy is to search the night sky with simple binoculars. The best simple binoculars for astronomy use are 7 X 50mm or 10 X 50mm; the first number is always the power, and the second number is the size of the objective lens in millimeters. I use the term “simple binoculars” to describe binoculars that are relatively inexpensive, and work well when hand held. Also, simple binoculars serve other purposes such as bird watching or viewing sporting events. If you move up to specialized binoculars, they are much larger, more expensive, and cannot be handheld. These binoculars generally range in power from 15 to 40, and the size of the objectives can be from 70 mm to 100 mm.

Last month I discussed finding the planet Uranus with only 7 power binoculars. I hope some of you tried and were successful in finding this outer planet. The outer planets can be easy binocular targets, but only if they are near some bright star or another object that can be used as a “sign post” in the sky. Last month we used the Circlet asterism in Pisces to find Uranus.

Remember, an asterism is a group of stars that have a recognizable shape; example, the Big Dipper or the Northern Cross. So let’s start our binocular tour with the famous asterism, the Pleiades star cluster, which looks like a little dipper. The Pleiades is a star cluster and is easily visible to the naked eye, but it looks best with binoculars. The Pleiades is best viewed in the winter, but I decided to mention it now because it is a great binocular object, and it is just becoming an evening target. The Pleiades will slowly rise in east throughout the month, but will not be high overhead until mid-January. The Pleiades is also known as the Seven Sisters and although the naked eye can usually only see six stars, with binoculars you will see many more. Below is the location of the Pleiades looking east at 10 pm on October 15th.

Below is the approximate view through 7 power binoculars.

Although most of you have heard of or seen the Pleiades before, there is a much lesser known but interesting asterism that you should try to find this month. This little known asterism is perfectly positioned in the southwest sky this month. The asterism has three names; the Coathanger, Collinder 399, and Brocchi’s Cluster, and it is found in the constellation Vulpecula, under and to the left of the Northern Cross. However, the stars in the Coathanger are not associated with each other as in an actual star cluster, but this asterism is merely a chance lining up of stars, ranging in distance from 200 to 1100 light years away. What you will see through your binoculars is ten stars in the shape of an upside-down coathanger. I have always found it surprising that so many amateur astronomers have never heard of this asterism.

Here is a hint to help you find it. Look to the west anytime this month and find the Northern Cross asterism; which comprises most of the constellation of Cygnus the swan.  This asterism is in the shape of a Christian cross, and in the autumn, it is positioned somewhat upright. The bottom star of the cross is a beautiful double star called Albireo.  Using 7 power binoculars, place Albireo near the 2 o’clock position in your binocular’s field of view (red circle).

Then move your binoculars slightly to the upper right, (see large arrow) and the Coathanger will pop into view; see image below.

An interesting note: The Coathanger asterism, shown below, is always seen upside down as it moves from east to west from June through November.

If you travel to the southern hemisphere, it will always be seen right-side up.

To find the Coathanger, we used the double star Albireo. Albireo is in itself an interesting binocular object. Indeed, Albireo is my favorite star. Using 7 or 10 power binoculars, on a clear night, look carefully and you will see that not only is Albireo an obvious double star, but one star is deep blue in color, and the other star is golden yellow.

The image below is through a telescope at about 100 power, but Albireo is quite impressive through any telescope beginning at only 25 power.

One final binocular thought. Sometimes when you are just scanning the night sky with binoculars, well away from the Milky Way, you suddenly see an increase in the number of stars filling your field of view. This usually means you have found a star association.  A star association is a large group of stars that are associated with each other in their motions, and sometimes gravitationally. One such association is found around Mirfak, the main star in the constellation of Perseus. Use the “W” asterism in Cassiopeia to find Mirfak, and then move your binoculars across the region to see this star association.  See chart below.

Naked Eye Sights:  The Pleiades.  The Northern Cross.  Cassiopeia W.

Binocular Sights (7 to 10 power):  See above.

Telescope Sights (60-100mm:  Check out the star Albireo.


See you next month!

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