The Rotating Sky - Student Guide

pdf

School

State College of Florida, Manatee-Sarasota *

*We aren’t endorsed by this school

Course

ASTRONOMY

Subject

Astronomy

Date

Feb 20, 2024

Type

pdf

Pages

Uploaded by EarlFerretMaster49

Name: EV\Y’\ ‘F} ‘ﬂ Km(‘%m The Rotating Sky - Student Guide i. Background Information Work through the explanatory material on The Observer, Two Systems — Celestial, Horizon, the Paths of Stars, and Bands in the Sky. All of the concepts that are covered in these pages are used in the Rotating Sky Explorer and will be explored more fully there. {l. Introduction to the Rotating Sky Simulator Open the Rotating Sky Explorer The Rotating Sky Explorer consists of a flat map of the Earth, Celestial Sphere, and & Horizon Diagram that are linked together. The explanations below will help you fully explore the capabilities of the simulator. You may click and drag either the celestial sphere or the horizon diagram to change your perspective. A flat map of the earth is found in the lower left which allows one to control the location of the observer on the Earth. You may either drag the map cursor to specify a location, type in values for the latitude and longitude directly, or use the srrow kevs 1o make adjustments in 5° increments. You should practice dragging the observer to a few locations (North Pole, intersection of the Prime Meridian and the Tropic of Capricorn, etc.). Note how the Earth Map, Celestial Sphere, and Horizon Diagram are linked together. Grab the map cursor and slowly drag it back and forth vertically changing the observer’s latitude. Note how the observer’s location is reflected on the Earth at the center of the Celestial Sphere (this may occur on the back side of the earth out of view). Continue changing the observer’s latitude and note how this is reflected on the horizon diagram. When the observer is in the northern hemisphere the NCP is seen above the north point on the horizon at an altitude equal to the observer’s latitude. When the observer is in the southern hemisphere the SCP is seen above the south point at an altitude equal to the observer’s latitude. The Celestial Sphere and Horizon Diagram are also linked in that anv stars are added to the simulation are shown on both. There are many features related to stars. 0 A star will be randomly created by clicking the add star randomly button. 0 A star may be created at a specific location on either sphere by shifi- clicking at that location. (Hold down the shift key on the keyboard while clicking at that spot.) 0 You may move a star to any location by clicking on it and dragging it. Note that it moves on both spheres as you do this.

o0 Note that the celestial equatorial and horizon coordinates are provided for the “active” star. Only one star (or none) may be active at a given time. Simply click on a star to make it the active star. Click on any other location to make no star active. o If you wish to delete a star, you should delete-click on it. (Hold down the delete key on the keyboard while clicking on the star.) 0 You may remove all stars by clicking the remeve all stars button. 0 Note that stars are the vehicle by which you make coordinate measurements. If you want to make a measurement in either diagram — you place the active star at that location. e There are several modes of animation as well as a slider to control speed. 0 You may turn on animate continuously or for preset time intervals: 1 hour, 3 hours, 6 hours, and 12 hours. 0 If you click-drag a sphere to change its perspective while the simulator is animating, the animation will cease. Once you release the mouse button the present animation mode will continue. e This simulator has the power to create star trails on the horizon diagram. 0 A series of check boxes set the star trails option. Ne star trails is self- explanatory. Shert star trails creates a trail behind a star illustrating its position for the past 3 hours. Long trails will trace out a parallel of declination in 1 sidereal day. 0 Stars are created without trails regardless of the trail option checked. If either short or long trails is checked, the trail will be drawn once the simulator is animated. 0 Existing star trails will be redrawn in response to changes — the star being dragged on either sphere or changing the observer’s location. 0 What’s not in this simulation? — the revolution of the Earth around the sun. This simulator animates in sidereal time. One sidereal day (one 360° rotation of the earth) is 23 hours and 56 minutes long. You should think of this simulator as showing the Earth isolated in space as opposed to revolving around the sun. 1ll. Horizon Coordinates Question 1: Complete the following table involving the horizon coordinate system. You should predict the answers and then use the simulator to check them. Remember that you can measure coordinates by dragging the active star to that location.

Description Latitude Azimuth Altitude West point of the horizon Any @7@ Am Zenith Any Any QOA NCP 30°N (07 20 NCP 71°N o ]l SCP _52°8 1%0 5. 12.5oni Floed | 120 | 235 Intersection of CE and Meridian )32 5575 Intersection of CE and Meridian 0° 35° Question 2: The next page contains a diagram known as a 5 z Star | Azimuth | Altitude “fish-eye” view of the sky. Note that it is drawn like a sky- A o pewen chart which is held up above your head and mimics the sky B 90° 0° in that perspective. You should convince yourself that the C 180° 5o east and west directions are shown correctly. Assume that you are at a northern mid-latitude of 40° N. You will be asked to create stars at specified azimuths and altitudes. You will then be asked to make predictions about the locations and motions of the stars as time advances. After drawing in your predictions you should use the simulator to check your answer. If your original prediction was in error, redraw your star paths to reflect the correct motion. a) Draw in the location of the North Celestial Pole. Note that since this location is directly above the Earth's North Pole it will not move in the sky as Earth rotates. b) Draw in star A at the specified coordinates and assume that this is time t = 0 hrs. Az 205 AW 379 ‘What will be the coordinates of star A at t = 6 hours? Att=12hous? AZ 359.5 AR (o). H Att=24homs?_ AZ O AH 20 Draw in each of these locations and connect the path between the stars. For what fraction of the day is star A visible? Al } OF ’% T¢E d(/{‘% c) Draw in B at the specified coordinates and assume that this is time t = 0 hrs. What will be the location of star B at t = 3 hours? A2 \22.2 At %% 4

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

d) ace=showsz_AZ [ B]. 2 AV l’M.a' act=2hous?_AZ 211.0 A4 — 0.1 Draw in each of these locations and connect the path between the stars. For what fraction of the day is star B visible? iQ- / 'ZL} - 60 70 O’de‘fi Draw in C at the specified coordinates (as best you can) and assume that this is time t = 0 hrs. Estimate the coordinates of the star at t = 6 hours? /VL27—3 9 Al -32- 9 Att=12homs? A2 1T M At T 1 Att=24hous? A2 180 AH -5 For what fraction of the day is star C visible? _() 70 Neved 2\GES

Question 3: Think about the characteristics of a star that passes through your zenith point (still at 40° N). Use the simulator to determine the following characteristics of this star. Rising Azimuth = 3 7' % Setting Azimuth=_ 3 2(o0. D Declination = 5 % . q IV. Declination Ranges 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 (a very important marker in the sky since it is located very near the NCP). Use the constellations control to add the Big Dipper to the celestial sphere. Now manipulate the observer's location to estimate where on the Earth the Big Dipper can always be seen, where it sometimes can be seen, and where it never can be seen. (Hint: you will need to use the start animation control since the Big Dipper can be either above or below the NCP.) Repeat with Orion and the Southern Cross. Star Pattern Always Can Sometimes Can Never Can Be Seen Be Seen Be Seen Big Dipper HON-90 LHoN-40S |50s —os Orion @3 N - q@ S AY‘\/ whnexve .C;QN "A@’{ng\! S Southern Cross 355,9(‘}5 3’ N - 3‘5 33[\, ~‘C?D/\j

Question 5: In which of the 3 declination ranges (circumpolar, rise and set, or never rise) are stars A, star B, and star C found? Star A: (\ WCU\M()(\\GT sarB: K1Se an d Set Starc: NRVLY 115¢ Question 6: Let’s explore the boundaries of these 3 regions. Make sure you are still at a latitude of 40° V. create a star, select the long trails option for star trails, and animate for 24 hours so that a complete parallel of Star | Azimuth | Altitude A 0° 20° B 90° 0° C 180° -5° declination is made for the star. Now drag this active ¥ : star so that it is at the north point of the herizon. (Make sure the star is active so you can read off its coordinates.) Note that a star with a slightly smaller el declination would dip below the north point while a star that is closer to the NCP would obviously be circumpolar. Thus, this star’s declination is a limiting value for the circumpolar declination range. Complete columns 2 and 3 for each of the given latitudes. Latitude Nort!1 P(it:: Cir;ualltlg:lar %1:32] z:ii;:lt RisReaigiet N | T30 -+90 [ - 80 - “80 25°N + 5 15 - TY0| —leb +o5-"k 40°N +50° +50°10+90° | 50 +‘5()— “50 55° N +35 +35-t70| _35 + 2535 70N [ LD +70-+90|-20 =20 Now drag the star to the south point on the horizon and read off the star’s declination. This is a limiting value for the never rise declination range. You should now be able to complete columns four and five in the table above.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Question 7: Set the simulator up for an observer on the equator. Create some stars (~20) in the simulator and click animate continuously. Describe the circumpolar stars seen from the equator. | VIEIE. Q-2 N0 ClY’CLAY‘fw}C‘lﬂ’( SHArS S€en ynen e Uiy Question 8: Set the simulator up for an observer at the south pole. Make sure that there are still stars (~20) in the simulator and click animate continuously. Describe the circumpolar stars seen from the south pole. ]:V-P (\1 S‘! i "(:}%'{f f“g" 4 V HNat 1S Nisihe S Civeu vo*tfi“ /\V’)d all 'H’TE’, e oS Nre Neser Nse Hars. Question 9: Use your experiences from questions 6, 7, and 8 to help you state a general rule for identifying the three declination ranges given the observer’s ]anmde lﬂ’)‘@ dhserver's |lahtude. Covvecpondsfpthe alhitude of the CewShal pole s stans witi ’H’E olserver’s atrtude cfeqrfifi fBom Cetesh fote NEVEX Set (Cirtumpol lar), Stars w-ﬂd“frdhm*ﬂ 40° minuc obsener's latfude fom Celeshal pore Nexer (SE avove hor;zton V. Star Trails Question 10: Visualizing star trails is an important skill that is very closely related to declination ranges. Again set up the simulator for a latitude of 40° N, create about 20 stars randomly in the sky, turn on long star trails, and click animate continuously. The view to the right illustrates the |

Latitude | Direction Star Trail I’),e,scripti,qnx 7 T \. \ \ \ 40° N N 40° N S 40° N E 40° N w

* Pole above horizon (at zenith) 90° N ? 0°N E 0°N | N(orS) / o

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Question 11: Note that the simulator has a display option that iliustrates the angle that the celestial equator makes with the horizon. The angle will be nearly the same for other parallels of declination (i.e. star trails) near the east or west point. Use the table below to record the star trail angle for rise and set stars at various latitudes. @ Latitude Direction Star Trail Angle 10°N E 20. 25°N E o5 40°N E 50 55° N E 35 70°N E 70 Question 12: Describe a general rule for determining your Bt\llmde from looking at star sl Lcrh%udf’ Can e found] Dy (ommanng e [ocahon of olariS or e Sun o Hne? NN 2o TP |atitude You Qe :fz:m:i Tale’ o \c {9 uold o HNC oungfer ¢ é’”‘d(:f:rfi’—w N Qaove -Hae horizon, Hfolans | € at on ang e of 50 ﬂ@i}u@ the honzon, then the latitude 45 507 TV Sun, Wia%x%\/scie S Wt anoe. | NPT o e Sun 1S Yo abpue e hotizen, “?W” lapihude 16 50° (90-40=50) Ty

The Rotating Sky - Student Guide

Related Documents