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ONSTELLATIONS C Altitude Ruler The of the on its axis causes the to rise and set each evening. In addition, the of the Earth around the places different regions of the in our -time view. The is an extremely useful tool for finding stars and 10 in the sky, depicting not only what is currently in the sky but it also allows the 20 prediction of the rising and setting times of various celestial objects. 30

THE LAYOUT OF THE PLANISPHERE 40 50 The outer circumference of the dark blue circular disk (which is called the wheel) you’ll notice that the wheel is divided into the 12 months, and that each month is divided into 60 individual dates. The star wheel rotates about the brass fastener, which represents the 70 . The frame of the planisphere has times along the outer edge. 80 Holding the planisphere on the southern corner you'll see "midnight" at the top. Moving counterclockwise, notice how the progress, through 1 AM, 2 AM, and so on through "noon" at the bottom. The hours then proceed through the afternoon and evening (1 PM, 2 PM, etc.) back toward midnight.

Once you have the wheel set properly for the correct time and day, the displayed part represents what you see if you stand with the star and locator held directly over your head with the brass fastener toward the north. (Notice that the directions are also written on the corners of the frame.) Of course, you don't have to actually stand that way to make use of the Star and Planet Locator--this is just a description to help you understand what is displayed.

LOCATING & IDENTIFYING STARS

Stars are depicted by circles with increasing brightness represented by increasing diameter. The planisphere is designed to be held above your head so that it represents the stars in the sky.

Hold the planisphere by the South horizon corner above your head. Notice that East is to your left and West to your right. If you are looking North, then hold the planisphere by the North horizon. You’ll notice that the East horizon in now on your right and West on your left.

Rotate the inner disk so that May 15 aligns with 8 pm. Slowly rotate the inner disk so that May 15 now aligns with 8 pm, then rotate it to 9 pm, then 10 pm, and so on. What direction (clockwise or counter clockwise) do the stars move? From what horizon do the stars rise (N, S, E, W) and what horizon do they set (N, S, E, W)?

Direction______Rise______Set______

The is an imaginary line that runs through the North / South horizon, bisecting the sky into East and West . List two with prominent stars that can be found near the meridian at 10 pm on January 15.

Constellation Prominent Star(s)

Constellations 1 The stars “rotate” around a central point on the planisphere. What star do all of the stars in the sky rotate around? What constellation is the star located?

Star______Constellation______

ALTITUDE is a measure of the elevation an object is above the horizon. Objects on the horizon have an altitude of 0o, and objects at an altitude of 90o are located directly overhead, or at Zenith.

Place the Altitude Ruler so that the Horizon line is on the northern horizon. Measure the altitude of above the northern horizon.

Altitude______

This planisphere is designed for the night sky for locations with a of 40o N, such as Providence. How would the altitude of Polaris change for locations north of Providence such as Fairbanks, Alaska with a latitude of 65o N? What is the altitude of Polaris in Fairbanks?

How does the altitude of Polaris change for locations south of Providence, such as Miami, Florida with a latitude of 25o N? What is the altitude of Polaris in Miami?

Where on earth would you find Polaris on the horizon? Where would you find Polaris directly overhead?

Located on the meridian, a star or constellation at your Zenith (altitude = 90o) is directly overhead. , a bright star in the constellation (the Lyre) can be seen in April nearly directly overhead early in the morning before the sun has risen. What time would you see Vega at your Zenith on April 15?

Capella, in the constellation can also be found at our Zenith in the months. What time would you expect to observe Capella on January 1 at Zenith?

Constellations that are visible the entire are called circumpolar constellations. Rotate the planisphere throughout the year and record the names of four circumpolar constellations.

1. 2.

3. 4.

Constellations 2 N is a compass direction where the object (star, planet, NNW NNE sun or ) can be found in the sky. Along with altitude, NW NE these two measurements can accurately describe the position of an object at a point in time. WNW ENE Rotate the planisphere so that November 15 aligns with 10 W E pm and find the brightest star in the sky, , located in the constellation . Which direction along the WSW ESE horizon would you look? (Be specific, such as S, SSE, SE, ESE, etc ) SW SE SSW SSE ______

S Determine the altitude of Sirius. ______

Rotate the disk so that you observe the motion of the stars every month at 9 pm until April 15. Imagine that you walk your dog every night at 9 pm during the winter and spring months and you were to observe Sirius during this period. Would Sirius be found in the same part of the sky throughout the winter? Describe the changing position of Sirius during this interval of time. What motion of the earth is responsible for this observation?

Place the star Sirius in the southeastern horizon. Approximately what date of the year does Sirius make its appearance in this horizon at sunrise (5 am)? This time of the year is referred to as the “ of ”. Date______

Rotate the planisphere to 10 pm on your birthday. What constellations and stars are prominent near the meridian at this time of the year? Date______

Constellations Prominent Stars

This Star is the red eye of the constellation : ______

This Red Giant is the red eye of the bull in the constellation : ______

The “” is formed by the prominent stars , Vega, and . What constellations are these stars located?

During what months can the Summer Triangle be found around midnight on the meridian?

Constellations 3 MEETS MYTHOLOGY Locate and identify the following constellations.

The myth of Andromeda claims that her mother, Queen Cassiopeia, was so proud of her daughter's beauty that she boasted it surpassed even that of the of the sea. Such arrogance offended the gods, who released floods in retribution and threatened to destroy the kingdom. Andromeda was chained to a rock by the sea upon the orders of her father, , in the hope that her sacrifice to the sea-monster would appease the gods of the sea. While awaiting her fearful fate, the princess was heroically rescued by who exposed to Cetus the decapitated head of Medusa - a sight so horrifying and morbid that the monster turned to stone. was born from the union of Medusa and when Perseus threw Medusa's head into the sea. The winged horse is famed in mythology for creating a fountain of water at Helicon with a stamp of his hoof.

Canis Major and are the dogs of , the hunter, which lies immediately to the north- west. In this guise they are frequently shown as a dogs standing on their hind feet, waiting on the command of its master to spring after the hare.

THE SUN AND THE

Located on the planisphere is a dashed line, labeled the . This represents the path the sun makes through the sky during the year against the background stars. Throughout the year the sun’s altitude changes with the seasons. Since the sun rises in the east and sets in the west, the sun reaches a maximum altitude as it passes through the southern sky at a time called solar noon when the sun is at the meridian.

The “” line on the Locator is the , an extension of the Earth’s equator. These two lines intersect twice during the year. Locate the intersections when they appear in the Southern horizon along the meridian. Record the date as they appear in the South horizon window on the Locator. What is the significance of these dates?

What dates are the ecliptic and equator furthest apart? What is the significance of these dates?

Rotate the planisphere to measure the altitude of the sun at noon today by placing the date in the Southern window of the plansiphere. Use the Altitude Ruler to measure the altitude of the sun (ecliptic) above the southern horizon.

Repeat the process for the dates in the table below.

Season / Date Altitude

Today /

Winter / December 21

Vernal / March 21

Summer Solstice / June 21 Autumnal Equinox / September 21

Constellations 4 What is the change in altitude of the sun from to season? What feature of the Earth’s motion which is responsible for this seasonal change?

To determine the azimuth (location at the horizon) and the time for sunrise, rotate the dial so that today’s date is in the center of the Eastern window on the planisphere. The azimuth and time is determined where the sun (ecliptic) intersects the horizon. Use your pencil to form a straight line through this point and Polaris (the grommet) to estimate the azimuth and time for sunrise.

The process for sunset is similar to that above except place today’s date in the Western window.

Sunrise Sunrise Sunset Sunset Season / Date Location Time Location Time Today / Winter Solstice / December 21 Vernal Equinox / March 21 Summer Solstice / June 21 Autumnal Equinox / September 21

THE

As you have seen, the dashed line on the planisphere marks the ecliptic. As our Earth moves around in its orbit, the Sun, the Moon, and the planets also appear along this line. The ecliptic therefore represents the plane of the . Of the nine planets, five are easily visible without a telescope.

The table on the reverse side of the plansisphere contains the constellation in which a planet can be found for during this year (2011). In the sky, the planets will appear as bright points of light, sometimes much brighter than the surrounding stars.

What planets are visible around 10 PM tonight? What planets are visible around 3 AM?

10 PM Planet Constellation Altitude Azimuth

3 AM Planet Constellation Altitude Azimuth

Examine the chart again and provide an explanation why the planets and tend to remain in a given constellation for several months while can be found in different constellations throughout the year.

Why are and seen only during the morning (MOR) or evening (EVE) hours?

Constellations 5 THE PLANISPHERE: POST-LAB

1. On May 1st at 8:30 pm what prominent star is about to set in the west?

2. On May 1st at 11:30 pm what star is near your zenith?

3. On Feb 1st at 1:00 am, what is the altitude of Polaris?

4. What does the ecliptic represent?

5. Where will the sun rise on December 25? When?

Where will the sun set on December 25? When?

6. Where will the sun rise on July 4? When?

Where will the sun set on July 4? When?

7. What is the altitude of the sun at noon on December 25? July 4?

8. Why are only certain constellations designated as constellations of the ?

9. What sign of the zodiac is your birthday?

10. Approximately what date would you go outside to see this constellation at midnight on the meridian?

11. What time is Orion in the southern sky today? Two months earlier? Two months later?

12. What two prominent stars are located in Orion? Where are they located within the constellation?

13. What time does the star Sirius rise on December 1? What time does it set? How many hours is Sirius visible in the sky on December 1?

Constellations 6