Name: ______________________________ Date: ________________Period: _______
Basic Coordinates & Seasons

Go to: http://astro.unl.edu/naap/motion1/motion1.html
There are three main sections to this module: terrestrial coordinates, celestial equatorial coordinates, and understanding how the ecliptic is related to seasons on the Earth. Each of these sections has its own simulator(s). The background material necessary to utilize these tools is contained in each section.

Celestial Equatorial Coordinates
Work through the introductory material on the page entitled Celestial Equator,
Declination, Right Ascension.
•

Open either the Flat Sky Map Explorer or the Sky Map Explorer.

•

Familiarize yourself with the set of features (cursor movement, shifting the map, decimal/sexagesimal). •

Make sure that you understand what each check box does.

Question 1: Note that there is a star at the very top of the map. That’s Polaris. What is it’s declination?
Question 2: Find the constellation of Taurus as shown in the box below and measure the right ascension and declination of its brightest stars Elnath and Aldebaran. Note that
Taurus is one of the Zodiac constellations.
RA
DEC

RA
DEC

The Sky

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Name: ______________________________ Date: ________________Period: _______
Basic Coordinates & Seasons
Question 3: Right ascension starts from the celestial meridian and increases as it goes
East. Knowing that, which direction (right or left) is East on this map?

Question 4: Complete the following table of positions on the ecliptic.
Ecliptic Location

Approximate Date

Vernal Equinox

March 21

Summer Solstice

Right Ascension

Declination

June 21

Autumnal Equinox
December 21
Question 5: What does the shape of the ecliptic look like on the flat sky map? What is the range of declination values of the ecliptic? If you took an average of those values, what would that line resemble?

Seasons and the Ecliptic
Go back a page. Work through the introductory material on the page entitled Orbits and
Light.
•

Open the Seasons and Ecliptic Simulator.

•

Read the guide that goes with this simulator (class set) and answer the following questions. Question 6: The table below contains entries for the coordinates for the sun on the ecliptic as well as the latitude at which the most direct and least direct rays of the sun are hitting. Use the simulation to complete the table.
Date

RA

DEC

Latitude of
Most Direct

Latitude of Least
Direct Ray

2.9 h

+16.5°

16.5° N

73.5° S

February 5
March 21
May 5
June 21
August 5
September 21
November 5
December 21
The Sky

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Name: ______________________________ Date: ________________Period: _______
Basic Coordinates & Seasons
Question 7: Using the data in the table above,

state the relationship between the

declination of the Sun and the amount of sunlight falling on the northern and southern hemispheres. Question 8: The region between the Tropic of Cancer and the Tropic of Capricorn is commonly known as the tropics. Using the sunlight data table from question 11, explain it is almost always warm in this region.

Question 9: Using the sunlight data table from question 11, explain the significance of the region north of the Arctic Circle and the region south of the Antarctic Circle.

The Sky

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Name: ______________________________ Date: ______________ Period: _________
The Rotating Sky – Student Guide

Go to : http://astro.unl.edu/naap/motion2/motion2.html
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.

•
•

Read Introduction to the Rotating Sky Simulator.
Open the Rotating Sky Explorer

Horizon Coordinates
Question 1: Set the latitude and longitude to near Houston (30ºN, 95ºW). Now add a random star. In the horizon diagram window, drag the star and place it in the zenith.
Looking back at the celestial sphere view, what is the declination of the star that would be in the zenith in Houston?
Question 2: Think about the characteristics of a star that passes through your zenith point
(still at 30° N). Use the simulator to determine the following characteristics of this star.
Rising Azimuth = _____________________
Setting Azimuth = _____________________
Question 3: What is the angle between the celestial equator and the horizon for each of the following latitudes:
Latitude

Angle

0º
15º
45º
60º
90º

Question 4: In the celestial sphere view, select the star from before and set the right ascension and declination both to zero. What two lines cross at this point?

The Sky

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Name: ______________________________ Date: ______________ Period: _________
The Rotating Sky – Student Guide
Question 5: Set animate for 6 hours, and click “start animation”. Does this star cross the meridian? Animate for one more hour, and note the star’s position. About how long does it take a start to go from being over Greenwich England to Houston?

Question 6: Show the circumpolar region. Note how big the circumpolar region is for
Houston. Now let’s compare that to the north pole and equator. Go to the north pole by changing the latitude to 90ºN. Note the size of the circumpolar region. Now go to the equator by changing latitude to 0º, and noting the circumpolar region’s size. Based on what you just saw, how does the size of the circumpolar region relate to latitude?

Declination Ranges
Question 7: 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.
Always Can

Sometimes Can

Never Can

Be Seen

Star Pattern

Be Seen

Be Seen

Big Dipper
Orion
Southern Cross

The Sky

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