March 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 March 15^th. For March, your best viewing nights will be from March 4^th through March 19^th. The Star chart below is set for Florence, SC on March 15^th at 9 pm.

How to locate any object in the night sky:

This month I would like to get quite technical and describe in detail the method I use to locate any object in the night sky, using a laptop and an astronomy program. This method is so good, that I can locate an object even if I cannot actually see it!

First pick out the scope you plan to use for the night. In this example I chose my 100 mm binoculars. Note: This technique can be used with any pair of binoculars or any telescope. Next I will decide to view/search at 25 power. Note, 25 power is a good choice to search for most amateur astronomy targets, because of the wider field of view, it is easier to locate an object, and then once located, you can place in high power eyepieces.

Next I turn on my laptop computer, and open up my astronomy program, Starry Night Pro.

There are two settings that have to be placed. The first setting is called FOV (field of view); this a one time setting. Turn your scope to any area of the sky; I find it preferable to use a constellation. Choose two stars that are at the opposite edges of your field of view, this may take some searching; below I used two stars in the head of the constellation Hydra.

Now go to Starry Night, change the setting of the cursor from adaptive to angular separation. Using the cursor, find the angular separation of the two stars you choose. Example, for the eyepiece I choose, the separation was 2.3 degrees.

Now open up the FOV window, choose new entry, then name the eyepiece, example Oberwerk 25 X 100, and enter 2.3 degrees.

Now any time I use this scope and eyepiece, I open up FOV, click on Oberwerk 25 X 100, and the circle on the star chart represents what I see through my telescope, see below. Note: You can open more than one FOV circles at the same time.

The second setting must be inserted each time you use your scope. Next turn your scope to any point in the sky; again, it is better to look at a familiar area, such as a constellation. Then with your FOV circle activated, compare the faintest star you can see in your eyepiece with the Starry Night view of the same location. With the cursor set at adaptive (normal setting), place the cursor on one of the faintest stars visible through your eyepiece, and check the listed magnitude; I usually do this on two or three stars. See below the faintest star found visible was magnitude 8.12.

Next click on Options, then scroll to stars and click on stars. This will open a box that has a slider that will allow you to set visible star magnitude. Move the slider to match the magnitude of the faintest star you could see.

When you are done with both settings, what you see anywhere in the sky through the eyepiece of your scope, is exactly what you see inside the FOV circle on the Starry Night screen.

Now let’s go find a target. Let’s try for a somewhat difficult Messier target, M51 (The Whirlpool Galaxy) in Canes Venatici. This is a beautiful object when seen through a large amateur scope, see below.

Let’s assume it is 10 pm on March 15. First I set up my scope and laptop and open Starry Night Pro. Next I click on FOV at the left of the screen and then click on Oberwerk 25 X 100, which places the correct FOV circle on the screen. Next I check out various places in the sky as described above to find the dimmest star I can see at 25 power; assume the dimmest is magnitude 8.12 (not a good night). I then go to the options on the left of the screen, go to stars and set the limiting magnitude at 8.12; all set!

Looking at my Starry Night screen, I can see that M51 is near the star Alkaid, the last star in the handle of the Big Dipper.

On Starry Night, I then zoom in on Alkaid and position my FOV circle so it “points towards” my target. This places the star Alkaid near the 8 o’clock position on the circle.

I now note that if I move my scope about one FOV in the 2 o’clock direction, I should see only three stars in a triangle. If I see a “smudge” on the right side of the triangle, it can only be my target, M51.

I can then increase my power to better view this galaxy. If I cannot see the target at all, it is just a bad viewing night, but I still can enter into my log book, “Located M51, but could not see it.”

Note: Although this example used binoculars, which see objects as your eye views them, Starry Night can be set for any viewing configuration, upside down, and/or reversed to match the scope you are using.

Naked Eye Sights: The brilliant planet Venus returns as the “Evening Star” just after sunset towards the end of the month.

Binocular Sights (7 to 10 power): Only month possible to find all the Messier Objects in one night.

Telescope Sights (60-100mm): Check out Saturn from mid-month onward.

See you next month!

February 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 February 13^th. For February, your best viewing nights will be from February 3^rd through February 19^th. The Star chart below is set for Florence, SC on February 15^th at 9 pm.

Vesta:

I am going to make a guess that anyone who reads this column and enjoys amateur astronomy has seen most if not all the common night time objects except one, asteroids, primarily because they can be quite difficult to find. If you have not yet seen an asteroid, this is a good month to start. The asteroid to locate is called Vesta.

Vesta is an irregular shaped “rock” with a diameter of about only 330 miles, at a distance of over 100 million miles; quite a challenge for an amateur! Vesta is formally called 4 Vesta because it was the 4^th asteroid discovered. Vesta was discovered in 1807 and is the second largest asteroid; Ceres is the largest with a diameter of about 600 miles. Also, Ceres unlike Vesta is large enough to be spherical, and is therefore classified as a dwarf planet along with Pluto. However, Vesta does hold the honor of being the brightest asteroid, which will also make it easier for you to see. Below is Hubble’s view of Vesta.

Here is another interesting Vesta fact. In October 1960, some men mending fences in Australia saw a large meteor fall to earth. Eventually the site of this meteor’s impact was located, and pieces of the meteor were recovered. It was later determined that this meteor was a piece of the asteroid Vesta! How did they know it really came from Vesta? A scientific method known as infrared spectroscopy is used to scan certain objects and give a type of “fingerprint” of the material. It was found that telescopic infrared spectroscopy of Vesta was a “fingerprint” match of the Australian meteorite. Years later, observation of Vesta by the Hubble telescope showed a massive crater covering a large portion of Vesta; likely the source of the meteorite. Over the years, many other Vesta meteorites have been discovered around the world. These Vesta meteorites are called HED meteorites; a name derived from their chemical composition.

So how did astronomers over the last 200 years discover asteroids? In the beginning, it was totally by chance. An astronomer may have been studying a particular star or other object for several hours or nights. In the process, it was noted that one of the “stars” in the field of view moved. This moving speck of light turned out to be one of many small pieces of rock, which we now call asteroids. The astronomers were also able to determine that these asteroids were in an orbit around the Sun, between the orbits of Mars and Jupiter. Once astronomers were aware that these objects existed, they started to look for new asteroids. The discovery of new asteroids moved slowly until the development of astrophotography at the end of the 19^th century. At that time, several astronomers had discovered a total of 323 asteroids. In 1891 when an astronomer Max Wolf began using astrophotography he discovered another 248 just by himself! By the late 1900’s, a total of a few thousand asteroids were discovered. The next “giant leap” occurred with the use of digital astrophotography combined with computerized analysis. Just one asteroid searching team called LINEAR has alone discovered over 97,000 new asteroids! Below is an image of some dwarf planets beyond the orbit of Pluto, and some asteroids compared to the size of the Earth, note the size of Vesta.

So now it is your turn, and you only have one asteroid to find this month. Why did I choose this month? Since these are tiny and somewhat difficult objects to see, it is good to have a marker in the sky to help out. On February 16th, Vesta moves between the stars Algieba and 40 Leonis in the constellation of Leo the Lion. On that night, Leo will be well above the horizon by 9 pm. Algieba is easily seen and is part of the backwards question mark forming the front of Leo. The chart below shows the location of Algieba in the Leo question mark.

When you look at Algieba with simple binoculars, you will see the star 40 Leonis below and to the right. The charts below show the position of the asteroid Vesta in relation to these two stars over a period of three nights.

So on these nights, at about 8 pm, use a pair of binoculars to locate these two stars and Vesta. Next, make a sketch of the objects you see. Then check again at 10 or 11 pm, and see if the object you thought was Vesta moved. If you are not sure, keep your sketch, and check that location the next night. With luck, you should be able to make your first asteroid sighting. Over the months I will tell you about any other easy to find asteroids.

Naked Eye Sights: Observe as Orion begins its departure in the West while the main constellation of spring, Leo, arrives in the southeast.

Binocular Sights (7 to 10 power): Main target this month is the asteroid Vesta. In addition, the great sights such as the Pleiades and the Orion Nebula are still visible.

Telescope Sights (60-100mm): Mars is now high in the sky. If you have been waiting for the return of Saturn, it is visible in the east after 10 pm at the end of the month. Saturn’s rings will slowly open up throughout 2010.

See you next month!