Grab your clickers please

Bell Work Briefly explain how an astrolabe works

Scale Scale Description 4 Through independent work beyond what was taught in class, you could: investigate the location of seasonal constellations in the local sky. predict location of constellations at future times. determine the celestial equator, latitude and position of the Pole Star for a given position on the Earth. determine the distances of stars in a given constellation to each other and to Earth. 3 You will be able to: describe and apply the coordinate system used to locate objects in the sky. distinguish the various methods of measuring astronomical distances and apply each in appropriate situations. 2 You will be able to: determine the meaning of symbols, key terms, and other astronomy specific words and phrases as they are used in context to relevant topics label diagrams with degree measurements describe how or why different units of measurement are needed for distances in space 1 You will be able to label diagrams with degree measurements list the different units of measurement needed to measure distances in space

If you were absent yesterday….Please tape your constellation lab into your journal above your constellation notes. Also, you need to make an astrolabe, I have all the materials for you. Come take a picture of the next few slides

Copy this in the top half of your journal’s right page ObjectAngle of Altitude #1degrees #2degrees #3degrees #4degrees

Copy this on the top half of your journals left page Sun MeasurementDateTimeAngle of Altitude #1Monday 9-14degrees #2Monday 9-21degrees #3Monday 9-28degrees #4Monday 10-5degrees

Copy this on the bottom half of your journals left page Moon MeasurementDateTimeAngle of Altitude #1Monday 9-14degrees #2Monday 9-21degrees #3Monday 9-28degrees #4Monday 10-5degrees

To become familiar with how an astrolabe works, practice measuring the altitude (angular height) of trees or buildings. To make a proper measurement, look at the top of the object through the straw. Have someone read the altitude in degrees from the side of the astrolabe. The point where the string crosses the scale is the proper measurement. Practice using your astrolabe by measuring and recording another tree or building of a different height. Now that you have an understanding of how an astrolabe works, you can use it to measure the motion of the Sun.

Because it is harmful to look directly at the Sun, a new method for measuring the Sun's altitude must be used. Hold the astrolabe so that the straw points in the direction of the Sun. Do not look through the straw. Aim the straw so that you see the shadow of the straw on your hand. Move the straw slightly until a small circle of light forms on your hand. The straw is now pointing directly at the Sun. Ask someone to read the Sun's altitude (in degrees) where the string crosses the scale. Take note of the time of day the reading was made. One day a week, at the same time each day, measure the altitude of the Sun with your astrolabe. Make three consecutive measurements and record them in the chart provided. Be sure to include the date. As the weeks progress, look at your measurements of the Sun's altitude. Can you detect a change? Is the altitude increasing or decreasing? Is there a pattern of change? How can you explain these changes?

Today’s question: How can we measure distances and direction in the sky? Some words I need to know: Zenith, Meridian, Altitude, Azimuth, Nadir, Start on the bottom of the right side of your journal. The Celestial Sphere

Celestial Sphere definition: The huge imaginary sphere on which all the objects in the sky were once considered attached. (was also thought to be centered on earth) Though it’s not actually the case, it’s convenient for describing locations of objects in the sky. (paraphrase this) Similar to an upside-down bowl covering the earth Celestial Sphere

1.3 The “Obvious” View The celestial sphere: Stars seem to be on the inner surface of a sphere surrounding the Earth They aren’t, but we can use two-dimensional spherical coordinates (similar to latitude and longitude) to locate sky objects

Based on the point of view of the observer It works if you are near somebody Altitude – measurement of height in the sky 0-90◦ Azimuth – measurement around the horizon 0-360◦ Horizontal Coordinate System

Altitude of Sun Azimuth of Sun time 11am1pm3pm Example - Sun

Altitude – degrees – height Azimuth – degrees - compass direction Remember:

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Put in a numeric answer What would the azimuth be for the flag?

Also put in a numeric answer What about for Worm?

This is why it works great for people near each other, but not so much for people far away from each other (opposite sides of the earth) What would the azimuth and altitude be for the projector mounted on the ceiling?

Summary of Horizontal Coordinate system Why were everybody's answers different based on where they were sitting? Is this a positive or negative thing? Why?

Was this easy to learn and use? Yes or No? Was this a positive or a negative? Why?

If you learned any of the vocab words from the beginning of the class, write down their meanings

similar to the longitude-latitude on the Earth's surface. Fixed with respect to the stars (preferred by astronomers). Equatorial coordinate system

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(1) Because the celestial sphere provides a natural means of specifying the locations of stars on the sky. Celestial coordinates are directly related to Earth’s orientation in space, but are independent of Earth’s rotation. (2) Distance information is lost.

lines that run north-south on Earth are lines of longitude and when projected onto the sky, they become lines of right ascension. the stars were used to measure time in the past, so right ascension (RA) is measured in terms of hours, minutes, and seconds and increases in an easterly direction. lines that run east-west on Earth parallel to the equator are lines of latitude and when projected onto the sky, they become lines of declination. Like the latitude lines on Earth, declination (dec) is measured in degrees away from the celestial equator, positive degrees for objects north of the celestial equator and negative degrees for objects south of the celestial equator.

Bottom of page 12 or 13: in 2-3 sentences, answer the question from the start of the activity using information from your notes. summarize