The Cosmic Explorer (600-2409) Operation Faxback Doc. # 33044 HOW TO SET UP THE COSMIC EXPLORER FOR ANY GIVEN DATE: As you know, the 3-D Star Map on the Cosmic Explorer shows you the nearby stars visible from our region of the Orion spiral arm of the Home Galaxy. The Star Seeker represents you, somewhere on Earth. The stars, galaxies, star clusters, and nebula we see from Earth seem to stay in place for years. Planets, however, are constantly moving so you will have to refer to the planet charts to find where they are in the sky. Let's say you want to see what stars are up on the night of July 10. Let's also say you live at about 25 degrees N. 1. Pick up the Star Ball and look at the Sky Calendar as you rotate the ball to the left. As you do this, the months of the year progress normally. Find July 10. 2. Set the Star Ball on the Power Base so that July 10 is just above the West horizon. Keep the equator aligned with the two arrows on the E and W cardinal points. You will see the words "EQUATOR HERE" printed on the horizon Ring. 3. Now you are set up for sunset on July 10. Notice how far North the sun sets at that time of year! The Sky is still too bright to see any stars. You will have to wait about 2 hours before the sky is dark enough to observe. By then, the Sky will rotate westward by 30 degrees. To adjust your Star Ball for 2 hours after sunset, turn the ball to the left so that the hour increments on the EQUATOR move from 8^h to 10^h. The Sky rotates at 15 degrees/hr. 4. Look at the Star Ball and you will see that Corona Borealis and Hercules are near the zenith. Leo is setting the West, while the three constellations whose brightest starts make up the super star pattern called the summer Triangle: are high in NE part of the sky. These constellations are Lyra, Cygnus and Aquila. 5. To keep track with the constantly rotating sky, use the hour markers on the Equator as references. The time of sunset depends on your attitude. For the observer at 25 degrees N latitude, as shown in Figure 8 and 9, sunset comes early at about 6:50 p.m. (1850). For an observer at 54 degrees N, sunset comes at about 8:30 p.m. (2030). In any case, note the time of sunset and look at the Star Ball to see which hour of RA is on the western horizon. For July 10, we saw that the 8^h is on the western horizon. To keep track of the turning sky, simply advance the Star Ball westward for every hour change on your clock. Remember, RA hours are broken into 60^m increments if you want to make smaller adjustments. As you can see, this is a very simple process. The more you use it, the easier the process becomes and your understanding and knowledge of the sky, its inhabitants and its motions, will increase greatly. PLOTTING PLANETARY POSITIONS The visible planets - (Mercury; Venus; Mars; Jupiter; and Saturn) - can be seen to move compared to the stars, which seem fixed in space. That is why we cannot print the planet positions on the Star Ball. Here is how to use the information in the Planet Position Table to locate the planets up to the year 2001. Let's stay with July 10 and let's pick 19993 as the year for our observation. The Planet Position Table shows the following information for July 1, 1993. (The planets will not change position much between July 1 to July 10 except for Mercury and Venus.) July 1, 1993: 8/7.9^h, -18 degrees (Mercury) 4/3.6^h, + 16 degrees (Venus) 11/10.5^h,+11 degrees (Mars) 12/12.4^h, - 1 degree (Jupiter) 22/22.2^h, -13 degrees (Saturn) Look at the coordinates for Mercury: Rounded off RA: 8 (8/7.9^h, -18 degrees) More precise RA: 7.9^h Declination: 18 degrees, South of equator (- means South, + means North) If you are not a telescope owner and just want to find the planets in the sky, use the rounded off RA value, 8^h in this case. Pick up the Star Ball and find 8l^hk on the equator; it is just to the right of Canis Minor. Mercury is on that hour circle, but where? Simple, the planets are always found near the Ecliptic on which the Sky Calendar is printed. So, if you look northward from the 8^h to the Ecliptic you will see that the planet Mercury would be between Gemini and Cancer on July 1, 1993. Where will you find Venus, Mars, Jupiter, and Saturn on the same night? Venus, at 4^h, is in Taurus and will be visible before dawn Mars, at 11^h, is in Leo, low in the west at first dark Jupiter, at 12^h, is Virgo, high in the west at first dark Saturn, at 22^h, is in Aquarius, very low in the east at first dark, but it will be in the sky all night! You need 30x in order to see its ring system. You may have to interpolate a bit for the faster moving planets (Mercury and Venus), but that is simple to do. Once again, with a little practice and patience you will become an expert planet plotter. OBSERVING OUTSIDE WITH THE COSMIC EXPLORER: Let's say you take the Cosmic Explorer outside on July 10. Set it up so that the W on the horizon Ring is pointed west (about 23 degrees south of the sunset point on July 10). Now, the other cardinal points will be correctly oriented; N with North, E with East, and so on. As the Sky darkens, rotate the Star Ball westward, as we described previously, to compensate for the Earth's rotation. Watch carefully for emerging bright stars and planets as the sky darkens. Soon, you will be able to trace out the dimmer stars and the constellations will become recognizable. Red Filter Use: Put the Red Filter over the light lens so that it is completely covered with the red light shining into the Star Ball. You will have enough light to see the constellation names, stars, and other printed information without degrading your night vision. You will have enough light to see the constellation names, stars, and other printed information without degrading your nights vision. You will see far more stars after about 20 minutes sitting under the darkening sky than when you walk from a brightly lit home into a dark night. Relax and enjoy the pleasures of cosmic exploration. Phosphorescent Stars: About 170 of the more than 850 stars printed on your Star Ball have been hand painted with a safe but bright phosphorescent acrylic paint. Use the white power light for a few seconds to excite the "phosphostars". With the lights out, indoors or out you can enjoy your personal glow-in-the-dark cosmos. BASIC ASTRONOMICAL DATA: Much is known about heavenly objects near us. By near, we mean out to about 1,000 Light Years. Each Light Year equals about 6 trillion (6 x 10^12) miles or about 63,240 Astronomical Units. Each Astronomical Unit is about 149,600,000 km or 93,000,000 miles. One final unit should be mentioned. It is very commonly used by astronomers and you may see it as you read more about the subject. It is called a parsec (pc) and it equals 3.26 Light Years. There are KPC (1,000 pc) and MPC (1,000,000 pc) and MPC (1,000,000 pc) units also. Miles and Astronomical Units are used for distances within the Solar System. Light Years and parsecs are used for distances out to 1,000 Light Years or about 300 pc. For distances to other galaxies, you will see KPC's or LY's used. EXPLANATION OF TERMS USED IN STAR TABLES Names: The visible NEAREST stars have common Greek and Arabic names, as do all of the 20 BRIGHTEST stars. Those stars with an apparent brightness number greater than 5 are not bright enough to have been given names. Those stars with names or letters followed by numbers are named for their discoverers (i.e. Barnard's*) or for the special star catalog they are found in (BD + 43 degrees 44). RA and DEC: As discussed previously, these coordinates are used to locate objects in the sky. The following section describes how to use the Degree Scale with the Star Ball to find the position of RA and DEC coordinates on the Star Ball. D: This is the Distance of the star from our solar system in light years. Spectral Type: The stars are very hot masses of luminous gas, mostly Hydrogen and Helium with a sprinkling of other elements. By examining their light after passing it through a prism or diffraction grating, astronomers can determine the color and energy balance of the spectrum, plus the pattern of absorption bands in the spectra. They then arrange the stars on a temperature scale, as indicated by their spectra. The scheme, once alphabetical, has been reorganized to look like this: O B A F G K M Hottest................Coolest Bluest.................Reddest Youngest...............Oldest Luminosity Class: The Luminosity Class of stars is generally used as a descriptor to Spectral Class. The reason is that there are many kinds of stars of very similar Spectral Type. For example, consider Star #19 or the Brightest Stars (Betelgeuse) and Star #20 or the Nearest Stars (CD-36 degrees 1593). They are both M2 spectral types, but look at their respective Mv's. Betelgeuse is a -5.6 and the other is a +9.6. The difference in magnitude is about 15. Each increment of magnitude equals a change of 2.512 times itself 15 times, or (2.512)^15. That is about a 1,000,000 times difference in luminosity or power output. Since both stars are the same temperature, the difference in power output must be due to -SIZE! Betelgeuse must be gigantic compared to the red, dwarfish CD-36 degrees 1593. And it is! The Luminosity Class Scheme is shown below: Ia: Most Luminous Supergiants Ib: Less Luminous Supergiants II: Bright Giants III: Normal Giants IV: Subgiants V: Main Sequence Stars, including Dwarfs, but not white Dwarfs (D) Radial Velocity: This is the velocity at which the star and our sun are approaching or receding relative to each other. A+ sign indicates the star is moving away from us, relatively speaking; a - sign indicates an approaching star. Apparent Brightness:(V) This stands for visual magnitude, or how bright the stars appear to be at their different distances from Earth. The higher the V of a star, the less bright it is. That means that a star with a V of 8 is less bright than a star with a V of 5. The V scale was established more than 100 years ago. Its zero point equals the brightness of the next brightest stars after the Sun, Sirius, Canopus, and Arcturus. Some stars have negative visual magnitudes. That is because they are brighter than most visible at night. The brightest sky objects, because they are so close, are the Sun and Moon, followed by the nearer planets. If a small letter v follows the value of the star's brightness, that means the star varies in brightness. Factors that affect the apparent magnitude (or brightness) of a given star are its power output (luminosity); the transparency of space through which its light travels; and its color. Though space is usually thought of as empty, it is actually a dusty and gaseous region, especially in our part of the galaxy. Absolute Magnitude (Mv): This is the star's absolute visual magnitude. Astronomers need to compare stars to each other in terms of a standardized unit of distance. This distance is selected as equal to 10 parallax seconds of arc or 10 parsecs 10 pc, for short. At that standardized distance, the difference in a star's brightness or magnitude would be due primarily to its power output, or luminosity. Like apparent magnitude, the smaller the magnitude number, the brighter the star. Look at the MY column in Tables 3 and 4. You may be surprised to see that some of the stars that look the brightest (with the smallest Mv) are not very powerful sources of energy compared to less bright stars that are very much further away. USING THE DEGREE SCALE AND RA ON EQUATOR TO LOCATE POSITIONS ON THE COSMIC EXPLORER: There are 41,253 square degrees on the Star Ball. We have printed about 868 stars plus several non-stellar objects. You can quickly locate a star or object by using the RA and DEC coordinates. Let's say you want to find the star Procyon, which is listed on the 20 nearest and the 20 brightest stars. Its coordinates are: 07h 39^m +5 degree. Start by picking up the Star Ball and looking along the Equator to find the 7^h. See it, just east of Orion. Next, estimate where the 39m mark would be between 7^h and 8^h. You can figure it is about 2/3 of the way to the 8^h increment. Now align the -0 degree mark on the degree scale with the center of the Equator. Do this so that the right edge of the Degree Scale is at the 7^h 39^m point. Next, look at the 5 degrees mark on the Degree Scale. It should be right on, or very close to, the star Procyon. Remember, most of the brightest stars are phosphopainted-another helpful clue. Try this method for several other stars and non-stellar objects. You will soon find it a very simple and quick procedure. You can also use this method to find any comets, novas, or supernovas which may appear from time to time in news reports. The coordinates are often given too. Now you have a way to locate them on the Cosmic Explorer and then in the night sky. Knowledge is Power! Table 2 Bright non-stellar objects visible from earth that are printed on the star ball: (See Faxback Doc. # 33320 for Tables 2 through 6) (BR/EB 5/10/96)