The Rotating Sky Lab - Allison Price

use the simulator to check them. You can check (and correct) your answer by creating an active star and entering the altitude and azimuth you think is correct. Description Latitude Azimuth Altitude East point on the horizon Any 90º 0º Zenith Any Any 90º NCP (North Celestial Pole) 15ºN .8º 15.1º NCP 48ºN 1.2º 48.1º SCP (South Celestial Pole) 45ºS 180º 44.4º SCP 50ºS 180º 49.4º Intersection of CE (Celestial Equator) and Meridian 48ºN 183.6º 41.9º Intersection of CE and Meridian 35ºS 355.8º 54.9º Question 2: Assume that you are at latitude 48° N, which is the approximate latitude of Spokane. When making predictions about the future locations of stars A, B, and C, use the diagram on the top of the next page that depicts a “fish-eye” view of the sky. Remember that the sky appears to rotate around the NCP, which is a point at altitude = 48°, azimuth = 0° in the diagram (as seen from Spokane). Try making your predictions first, and then use an active star within the horizon diagram view simulator to check (and correct) your answers. a) Assume star A is at the specified coordinates at time t = 0 hrs. What will be the alt/az coordinates of star A at t = 12 hours? Question 2: At t = 24 hours? Question 3: For what fraction of the day is star A visible (above the horizon)? NAAP – The Rotating Sky 3/9 alt 81°, az 0° alt 15°,az 0° It's visible all day. Star Azimuth Altitude A 0° 15° B 90° 0° C 180° -10°

Declination = IV. Declination Ranges The area of an observer’s sky where stars can always be seen is called the circumpolar region; the area where stars can sometimes be seen in the rise and set region; and the area where stars can never be seen is the never rise region. Note that you can select these three regions in the simulator by checking the appropriate boxes under Appearance Settings . For an observer at a specific location on Earth, it is the declination of the star that determines which of the 3 regions it is found in. In this section you will be investigating these different regions. Question 4: The two end stars of the Big Dipper are known as the “pointer stars” since a line drawn through them points toward Polaris (an important marker in the sky since it is located very near the NCP). Use the s tar patterns control to add the Big Dipper to the celestial sphere. Now manipulate the observer's location on Earth to find a point (in latitude) where the Big Dipper can always be seen (circumpolar), where it sometimes can be seen (rise and set), and where it never can be seen (never rise). It will be helpful to turn on the long star trails when running the simulation to see whether or not the stars go below the horizon. You only need to find the latitude of one location that satisfies the given conditions, and record that latitude in the table below. Star Pattern Circumpolar rise and set never rise Orion The Orion cannot always be seen. 48°N 90°N Big Dipper 48°N 2.3°S 55.2°S Southern Cross 90°S 5°N 90°N Repeat with Orion and the Southern Cross. All stars within the pattern must be visible (above the horizon) to be counted as seen . Question 5: In which of the 3 declination ranges (circumpolar, rise and set, or never rise) Are the stars A, B, and C from question 2 found, assuming you are at latitude 48° N? Star A Circumpolar NAAP – The Rotating Sky 6/9 48.9°

region around the north celestial pole. Realize that we need to imagine what these trails would look like from the stick figure’s perspective. Question 9: Check the box in the simulator that shows the angle between the celestial equator and the horizon. The angle will be nearly the same for all circles of declination (i.e. star trails) near the east or west point of the horizon. Use the table below to record the star trail angles for stars that rise and set at various latitudes. Latitude Direction Star Trail Angle 12º N E 78° 25º N E 65° 48º N E 42° 55º N E 35° 73º N E 17° Question 10: Notice the pattern between the latitude and star trail angle. Describe a general rule for determining your latitude from looking at just star trail angles. Summary/Conclusion (5 points): Imagine watching the sky while taking a trip from the equator to the North Pole. Describe how the location of each of the following would change as you traveled from the equator to the North Pole: The North celestial pole , the celestial equator , the circumpolar region , and the star trail angles . NAAP – The Rotating Sky 9/9 The higher the star trail angle, the lower your latitude. The NCP changed from being at the same latitude as me which is 0° at the equator, to directly 90° above me. The celestial equator when I am at the equator is an imaginary line directly above me running east to west. As I travel to the North Pole the celestial equator moves south so by the time I reach the North Pole, it will be even with the horizon. The circumpolar region is non existent when I am at the equator, but as I travel north it grows visible as a dome from the NCP. When I start at the equator, the star trail angles are 90° and as I travel to the North Pole, it slowly decreases with my latitude to reach 0° when I arrive there.