quarta-feira, 17 de outubro de 2012

Identifying stars in the Sky

I have always wanted to know how to do this, and today I have finally identified some stars in the sky =) So I would like to share this information with everyone. To start with, use Google Maps or Wikipedia to find your location in terms of world coordinates. In my case, Wrocław center is located at 51°6'28" North and 17°2'18" East. Then go to a website which generates a Sky Chart for our current position and time, for example: http://www.fourmilab.ch/cgi-bin/Yoursky

In Yoursky you need to enter the latitude, longitude and also adjust how many stars should be visible by setting the appropriate number in the fields "Show stars brighter than magnitude", "Names for magnitude and brighter" and "Bayer/Flamsteed codes". One can use the same number for simplicity. I am simply looking through the window of my apartment in the center of the city, so very few starts can be seen from here, around 30, so I found that showing only starts with a apparent magnitude of 2.8 or greater was a good choice (greater grows towards smaller numbers).

Notice in the chart the blue line. It represents the equator. We can see a little bit of area under the equator from here. Exactly in the equator one can see all starts, from both sides, and in other places which see mostly starts from our half and a little bit of stars from the other half. As the earth rotates all stars will appear to rotate around a central point, and in the north hemisphere this is the start Polaris, also called North Start, as shown in the chart above. In the south the southern cross, called the constelation of Crux also, points to the southern point. Aproximately 3 times the size of the cross, going in the direction of the base of the cross, one can find the south pole.

With all of this in mind, we can now start locating stars! A very important thing to do is to use a real magnetic compass ("Bússola" in portuguese), or at least the magnetic compass from a iPhone or another smartphone. I was simply using from memory the information that my building is aligned to the axises, and that one window points to the south and the other to the north, and I wasted 1 hour trying to figure out which star is which because the positions simply did not match to my Sky Chart! Well, they didn't match because my guesses position for the North, South, East, etc, were wrong by about 30 degrees =) After I started using the magnectic compass if my iPhone everything started going to it's place and I finally found stars!!! =D

The easiest one to find was Jupiter. It was by far the brightest thing in my limited visible sky. One problem that I had at first is that in the Sky Map there is no "Jupiter" written. Instead they use the symbol "♃" which means Jupiter in astronomy. You can find a list of symbols here: http://en.wikipedia.org/wiki/Astronomical_symbols#Planets

After finding Jupiter I also found Capella, Nath and Aldebaran =) In the southern section I had more problem, and I am not 100% sure of which stars I found.

Ok, I guess this is enough for now. It should get any complete beginners with zero experience like I was until 2 hours ago into someone who can find the most basic stars with the help if the Sky Chart =) And after getting familiarity with this, probably one should be able to find those easily recognizable stars even without a Chart.

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