Assignment C3 Instructions & Worksheet (1)
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Feb 20, 2024
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Assignment C3 Instructions & Worksheet
In this assignment, you will see how the date impacts what is seen in the sky and several celestial events form. You will use a planetarium software to explore the sky in this assignment. Any planetarium software should be sufficient, Stellarium
is recommended because it is free for Windows, MacOS, and Linux.
The meridian is the line stretching from the north point on the horizon to the south point of the horizon going through zenith. For this assignment turn on the meridian in the planetarium software to
make it easier (go to , then View Settings, and check the box for “Meridian Line”). We’ve learned astronomers use two ways of writing times when observing. The primary way is to record the time in Coordinated Universal Time (UTC is the standard time zone used in Aviation, Navigation, and Astronomy.) The proper way to write the date is in ISO 8601 format YYYY-MM-DD and the time in a 24-hour clock UTC. For these observations you may use the local time zone with the 24-
hour clock. In Stellarium it is easier to input the Julian Date than change the software to a different time zone.
There is a User Guide available for Stellarium, found in the upper right corner of the website: Part 1: Impact of Time of Day
In this section, you will observe the impact of the time of day on the sky. You are free to choose any location with a latitude between 10°N and 55°N and any date in this year. Record your selections below.
1.
Setup:
Location
Location Name:
Latitude:
Longitude:
Date:
Set the planetarium software to your chosen location and date.
Set the time to sunset (defined as the moment the sun disappears below the horizon).
You will track (4) objects in the sky, of which Polaris and Alcor are mandatory. In addition, select a bright star near the eastern horizon and a bright star near zenith.
In the table below:
Record the azimuth of all four objects at Sunset.
Change the time to one hour after sunset and record the azimuth for all four objects again.
Keep increasing the time until you are at 8 hours after sunset.
Also, record the altitude of Polaris in the table.
Table 1: Data collected for Part 1.
Object
Sunset
+1
+2
+3
+4
+5
+6
+7
+8
Polaris (Azimuth)
Alcor
Polaris (Alittude)
2.
Are all objects visible all night?
Answer:
3.
Do all objects appear to move in the same direction? (Explain)
Answer:
4.
Did the altitude of Polaris change over the course of the night?
Answer:
5.
How can Polaris be useful to navigation?
Answer:
Part 2: How the Date Impacts the Sky
You are free to choose any location with a latitude between 10°N and 55°N and any date in this year. Record your selections below.
6.
Setup
Location
Location Name:
Latitude:
Longitude:
Date: A. Setup
Set the planetarium software to your chosen location and date.
Set the time to approximately three hours after sunset. The time of night should stay the same throughout the observations.
B. Daily change
Increase the day by one.
In the table, record the answer to the question. Which direction (North to South, South to North, East to West, or West to East) has the sky near zenith has moved from one observation to the next? Do not
worry about Polaris on the chosen day only on all other days.
Repeat until the table is full.
Table 2: Data collected for Part 2B.
Chosen day
+1 day
+2 days
+3 days
+4 days
+5 days
+6 days
+7 days
+8 days
Sky Motion
Polaris (Altitude)
Polaris (Azimuth)
7.
Is the change consistent form night to night?
Answer:
C. Monthly Change
Reset to your chosen day approximately 3 hours after sunset.
Increase the month by one (not the day this time).
In the table, record the answer to the question. Which direction (North to South, South to North, East to West, or West to East) has the sky near zenith has moved from one observation to the next? Repeat until the table is full. If during any month the sun is above the horizon, making it difficult to see the star, you can turn off the atmosphere. We are more interested in observing the locations of stars in this part of the assignment.
Table 3: Data collected for Part 2C.
Chosen month
+1 month
+2 months
+3 months
+4 months
+5 months
+6 months
+7 months
+8 months
Sky Motion
Polaris (Altitude)
Polaris (Azimuth)
8.
Is the change consistent form month to month?
Answer:
9.
Are the Altitude and Azimuth of Polaris as you expect them to be from month to month?
Answer:
D. Yearly Change
Reset to your chosen day approximately 3 hours after sunset. Increase the year by one (not the day or month).
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In the table, record the answer to the question. Which direction (North to South, South to North, East to West, or West to East) has the sky near zenith has moved from one observation to the next? Repeat until the table is full.
Table 4: Data collected for Part 2D.
Chosen day
+1 year
+2 years
+3 years
+4 years
+5 years
+6 years
+7 years
+8 years
Sky Motion
Polaris (Altitude)
Polaris (Azimuth)
10. Is the change from year to year what you expect?
Answer:
11. How often does the sky jump backwards?
Answer:
12. What could explain the sky jumping backwards some years?
Answer:
13. Based on all your observations is Polaris a usefully navigation aid?
Answer:
Note: for the purposes of this course UTC and UT1 can be treated as the same.
Julian Date Converter