Stellar Motions Lab 7 (1)
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Jan 9, 2024
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Stellar Motions Lab
This lab will use an application called the Rotating Sky. You will need to use adobe flash to run
this application so you will need to download this first if you do not have it on your computer.
Use the following link to open the application.
https://astro.unl.edu/naap/motion2/animations/ce_hc.html
The application opens with two views of the sky:
the left side provides the celestial sphere view,
showing the Earth in the center of the sphere of stars that surround it; the right side is the
horizon diagram view, this shows the sky as it would appear to us standing on the Earth and
looking up at the sky.
The green circle represents the ground and it has the four cardinal points
on it.
The celestial sphere view can give us the co-ordinates Right Ascension (RA.) and Declination
(Dec.) which are the fixed co-ordinates to the Celestial Sphere, while the horizon diagram will
give us the Altitude (Alt.) and Azimuth (Azi.) which are the co-ordinates that will change for an
object.
You can randomly add a star to the sphere by clicking on the add star randomly button in the
star control panel or you can place your mouse on the sphere (on either the horizon or celestial
sphere view) and then holding down the shift key and then left click on your mouse.
When the
star has appeared, you may move it anywhere on the sphere by clicking on it with your mouse
and dragging it to the position that you would like. By clicking on the star with your mouse you
can find the co-ordinates for that star, the RA and Dec will appear on the celestial sphere view
while the Alt. and Azi. will appear on the horizon diagram view.
Underneath the two views of the sky are four sets of controls for the application.
The one to the
far left sets the location of the observer on the Earth (the map shows the point on the Earth).
You will change the location by simply changing the longitude and latitude in the upper right-
hand corner of the box.
The next box to the left of this is the animation controls.
This is where
you can start and stop the animation to answer the questions. The third box is the appearance
settings, these setting will be turned off and on as requested by checking or unchecking the box.
The control furthest to the right is the star controls.
This will allow us to see certain
constellations or stars move across the sky as the application runs.
Part A:
Maximum altitude of the Celestial Equator and Altitude of Polaris.
In the appearance setting controls make sure that you have the following boxes checked: show
0hr, show celestial equator, show underside of horizon diagram, and show the angle between
the celestial equator and the horizon.
Add a star to the diagram and move it so that it is on the
North Celestial Pole, use the celestial sphere view and try to get the Declination of the star as
close to +90° as possible, note that it will be hard to get exactly +90° but as long as you are
within a few tenths of the degree it will be fine.
You should also make note of this when your
answer your questions for the altitude of Polaris.
1.
Set the location for an observer at the North Pole by changing only the latitude to
90° N, note your longitude does not matter at this point as all longitude lines meet at
the poles.
a.
What is the angle between the celestial equator and the horizon?
_____0______
b.
What is the altitude of Polaris above your Northern horizon?
___90________
2.
Set your location for an observer at the equator by simply changing your latitude
to 0° N. Note: again, your longitude does not matter because you are on the equator.
a.
What is the angle between the celestial equator and the horizon?
____41.6_______
b.
What is the altitude of Polaris above your Northern horizon?
____90_______
3.
Set the location for an observer in New York City by setting the latitude to 40° N
and the longitude to 75° W.
Notice that the position of the dot on the Earth map will
move.
a.
What is the angle between the celestial equator and the horizon?
____50_______
b.
What is the altitude of Polaris above your Northern horizon?
_____40______
4.. Set your location for an observer in Hawaii with a latitude of 20° N and a longitude of
155° W.
a.
What is the angle between the celestial equator and the horizon?
___70________
b.
What is the altitude of Polaris above your Northern horizon?
____20_______
5. Using the answers from above can you predict, without the use of the application, the
angle between the celestial equator the horizon and the altitude of Polaris above the
Norther horizon for an observer
a
: at a latitude of 50° N? Explain how you predicted it.
Altitude of the CE: _____40____ Altitude of Polaris: ____50______
Explanation: _______The latitude always equals the
altitde_________________________________
b:
at a latitude of 75° N? Explain how you predicted it.
Altitude of the CE: _____75____ Altitude of Polaris: ______15____
Explanation: _________________The sum of both degrees must equal
90_______________________
Part B: Determining the range of Declinations for different latitudes.
For this section your answers will come from the celestial sphere view on the Rotating Sky
simulator.
You will add a random star to the simulator to help you answer the questions.
In your appearance setting there are three boxes which you will now check to turn on. The first
is the show never rise region, this it the south circumpolar zone which contains the stars that
never come above our horizon, so we never see these throughout the year.
The second is the
show circumpolar region, this is the north circumpolar zone which contains the stars that never
go below our horizon, which means that we see these all year long.
The third is the show rise
and set region, this contains the stars that will rise and set each night, the stars within this
region will change during the year depending upon the seasons.
You may at times to help you
want to turn on of these off and on.
1.
Set your location for an observer at the North Pole.
Add a random star to the
sphere.
a.
What is the range of declinations for a star that never rises, i.e. is in the
region of the sphere called never rise region? 0 to -90 degrees
b.
What is the range of declinations for a star that never sets, i.e. is in the
circumpolar region? 0 to +90 degrees
c.
What is the range of declinations for a star that rises and sets? No range
2.
Set your location for an observer at the equator.
a.
What is the range of declinations for a star that never rises, ie is in the
region of the sphere called never rise region? No range
b.
What is the range of declinations for a star that never sets, i.e. is in the
circumpolar region? No range
c.
What is the range of declinations for a star that rises and sets? 90 to -90
3.
Set your location for an observer in New York City,
d.
What is the range of declinations for a star that never rises, ie is in the
region of the sphere called never rise region? -50 to -90
e.
What is the range of declinations for a star that never sets, i.e. is in the
circumpolar region? +50 to +90
f.
What is the range of declinations for a star that rises and sets?
4.
Set your location for an observer in Hawaii, +50 to -50
g.
What is the range of declinations for a star that never rises, ie is in the
region of the sphere called never rise region? -70 to -90 degrees
h.
What is the range of declinations for a star that never sets, i.e. is in the
circumpolar region? +70 to +90
i.
What is the range of declinations for a star that rises and sets?
+70 to -90
Part C:
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1. Set your location for an observer at the North Pole.
A: In the star control setting, go to the toggle down for star patterns and check
the big dipper.
Set the animation running until you can see the big dipper at the front of
the globe on the horizon diagram, then stop the animation.
Tell me which region of the
sphere it lies in by checking and unchecking the boxes for never rise region, circumpolar
region, and rise and set region.
B: Now set the star control to Orion (uncheck the big dipper) and tell me what
region of the sphere it lies in. Rise and set region
C: Now set the star control to the Southern Cross, and tell me what region of the
sphere it lies in. Never rise regain
2. Set your location for an observer at the equator by simply changing your latitude to 0°
N,
A: In the star control setting, go to the toggle down for star patterns and check
the big dipper and tell me what region of the sphere it lies in. Rise and set
B: Now set the star control to Orion (uncheck the big dipper) and tell me what
region of the sphere it lies in.
C: Now set the star control to the Southern Cross, and tell me what region of the
sphere it lies in. Never rise
3. Set the location for an observer in New York City by setting the latitude to 40° N and
the longitude to 75° W.
A: Set the star control setting to the big dipper and tell me what region of the
sphere it lies in. Circumpolar
B: Now set the star control to Orion (uncheck the big dipper) and tell me what
region of the sphere it lies in. Rise and set
C: Now set the star control to the Southern Cross, and tell me what region of the
sphere it lies in. Never rise
4. Set your location for an observer in Hawaii with a latitude of 20° N and a longitude of
155° W?
A: Set the star control setting to the big dipper and tell me what region of the
sphere it lies in. Rise and set
B: Now set the star control to Orion (uncheck the big dipper) and tell me what
region of the sphere it lies in. Rise and set
C: Now set the star control to the Southern Cross, and tell me what region of the
sphere it lies in. Rise and Set
Questions
1. Set your rotating sky simulator for an observer in New York City.
Show the
circumpolar region and add about 7 to 8 random stars.
Move all of these stars into the
circumpolar region.
In the star controls click long star trails.
Start the animation and
watch the stars move, describe from an observer on the Earth’s point of view the motion
of these stars. Formed a circle moving clockwise
2. Clear all star trails from the simulator and now turn off the circumpolar region and turn
on the rise and set region.
Move the stars into this region, note they do not all have to
be above the horizon.
Start the animation and watch the stars move, describe from an
observer on the Earth’s point of view the motion of these stars. Formed a circle rotating
counter clockwise
3. What is the relationship between the altitude of Polaris and the latitude of the
observer?
There the same
5.
What is the relationship between the observer’s latitude and the number of
degrees in the circumpolar zones? Note that what the simulator calls the never rise
region is the south circumpolar zone and what it calls the circumpolar zone is the
north circumpolar zone. +50 and -50 degrees
5.
Where on the Earth do you need to live for the sun to reach zenith? The equator
6. Can you come up with a relationship for the ranges of degrees in equatorial zone
based on the observer’s latitude? The relationship is that there both opposites