What can we see in the sky? Focus on viewing the Big Dipper using Stellarium Software
Learning Objective: This activity is designed to get you out looking at the sky and to introduce you to a planetarium software, Stellairum, which is a useful astronomy tool that identifies objects in the sky based on location, time & date. A related discussion will allow you to share your thoughts and observing experience with your classmates, discussing what you learned.
Computer and internet access
printed data sheet: Big Dipper Stellarium Activity Data Sheet-1.rtf
digital camera or scanner
Total Time Required: Approximately 2-3 hours total AFTER you have installled the software. This Activity has 2 observations to be done at night with a clear sky. The observations can be on the same night or at least within no more that 7 days.
Exploration Study and Information
You will start by downloading the Stellarium software then print out and use the provided Data sheet found above or under the Dropbox tab, and then complete the Problems listed in Exploration below , and end the activity by sharing your thoughts/experiences with your classmates in a related Discussion.
First, please watch this video http://www.screencast.com/t/mDx23ZHL (you may need to copy and paste the URL in a new window if the video does not play).
Download the software from http://www.stellarium.org/. (link opens in new window) The program is super user-friendly, but to help you navigate please look through the Interface Guide: http://www.stellarium.org/wiki/index.php/Interface_Guide#Tour.(link opens in new window)
If you get lost performing the Problems below you can always close the Stellarium program and restart from the very beginning. It will be very helpful for you to have the above Interface Guide open in another window so that you can quickly reference it throughout the below Steps. Also, this activity is designed for people living in the northern hemisphere, please inform your instructor if you reside elsewhere.
Computer with Internet access
Printed Data Sheet found above or in the Big Dipper Stellarium Activity/Discussion Dropbox
Problem 1. Open the Stellarium program and bring up the sky as it is right now (your current date/time). It will be dark or light depending on whether it’s day or night outside right now (according to your computer’s internal clock). You should be facing South.
Try to adjust your screen to match the picture below (next page) so that you are seeing mostly sky and just a bit of the horizon (ground). Do this by clicking on and dragging the screen to move the horizon around and zooming in/out using the dial on your mouse or back/forward slash keys on your keyboard.
Check the time and date. If they are not correct set them to the correct local time and date. Also change the location to your specific location. The best way to do this is to hit F6 or click on the location icon, and then type your city in the Finder bar (with the magnifying glass), and then click on your city when you see it. (Or find the largest city listed that you are closest to.)
Write the Latitude and Longitude of your city on the Data Sheet.
Within Stellarium, you are now outside at the current time at your current location. What you should see is a picture of the sky with a lovely horizon below.
Move around so that you are looking West (click and drag the screen or use your arrow keys on your keyboard).
Now you will want to make time move forward (click on the double arrow 3 times – to stop click on the single arrow).
See what’s happening? The sky is moving. This is what the real sky does too. You have caused time to pass very rapidly. In fact you have nearly unlimited control over space and time! Look at the clock. You can make it move faster or slower or in reverse to ANY time you want. Watch how the sun and moon move across the sky. See how the sky gets dark or bright.
Now, using these controls, go back to today’s date and then move the time until the Sun has set and gone below the horizon and you can see more than 5 stars in the sky.
Stop there (hit the 7 key to stop time).
Fill in the time of sunset and the date on your data sheet.
Problem 2 Now move the horizon until you are facing north. Turn on the Constellation lines and labels.
Make time move forward a few minutes at a time. Don’t take big jumps of hours or days for this particular question.
Notice how the stars are going around in a circle. Notice that there is one star near the center of this circle. This is the North Star, the one star in the sky that holds still and doesn’t move (much).
Stop the motion.
Point your cursor at the North Star (Polaris) and click.
You will now see all kinds of information about that star. On the 3rd line is RA/DE (J2000) which stands for Right Ascension and Declination, (found in Chapter S1). Record the required information on your data sheet. The North Star is at just about 90 degrees declination (analogous to being at the North Pole on Earth).
Also note the Az/Alt(apparent) information, the azimuth (direction) and altitude of the object –fill this information in also.
Problem 3 Look for the Big Dipper which is part of the Constellation Ursa Major. Note: the Little Dipper, part of Ursa Minor, is near the Big Dipper and at the end of its’ handle is Polaris. Do not do your lab on this group of stars. Make sure you are observing the proper asterism (group of well-known stars).
It may sometimes drop partly below the horizon. The big dipper may be upside down. You can be sure you have it when the last two stars in the cup portion of the dipper point toward the North Star.
Now move time to about one hour after the sunset time you listed for Step 1 on the same date (it is best to use the Time/Date Window so that you can control the time precisely).
Sketch the seven stars in the big dipper exactly as you see them on the screen, with precisely the same orientation. If the handle is down, draw it that way. If the handle is horizontal, draw it that way.
Make clearly visible dots for each star. Then connect the dots to make the “big dipper” pattern, also include your horizon and how it appears relative to the “big dipper”.
Record the time and date on your data sheet. Please also include your horizon (which includes the direction you are facing).
Problem 4 Now advance time by four hours and repeat the process, making sure to draw the constellation the way you see it and the horizon. NOTE: If at any time in this or the next problems you can’t see the Big Dipper due to it being too light out simply click on the Atmosphere button located on the bottom panel, the icon that has a sun and cloud on it. This will let you view the sky as if Earth had no substantial atmosphere.
Problem 5 Advance time by another four hours and repeat the process, making sure to draw the constellation and horizon.
Problem 6 Reset your time back to one hour after sunset (the time you got in Step 1).
Changing only the month, set it to exactly two months from now at the same time.
Do not change the time of day! Make sure the time of day is exactly the same as in Step 1!
Repeat your drawing, making sure to draw the constellation and horizon. (Note: a change to or from daylight saving time over this time interval might affect this and the following drawing slightly. Don’t worry about it. It’s not serious.)
Problem 7 Change the month by another two months and repeat, making sure to draw the constellation and horizon.
Estimating the Altitude of an object in the sky
To measure altitude, simply use your fists. Start by holding one fist out in front of you with your arm fully stretched out like you are holding a vertical rope, and your arm and body making a 90 degree angle. This allows for the bottom of your fist to be “sitting” on the horizon in front of you. (From top to bottom, a fist at arm’s length is about ten degrees on the sky.) Start climbing this imaginary rope with one fist over another, touching. Count the number of “fists” from the horizon up to the object. So, if you counted 5 fists then your altitude would be 50 degrees, 6.5 fists would be 65 degrees, etc. If the horizon involves trees, buildings or a mountain, estimate where the horizon would actually be if there were no trees, mountains or buildings and use that as the starting point for your measurement. It will be important that you are able to measure the altitude within one fist (~10 degrees).
Problem 8 (Going outside) Go out at night when it’s clear.
Find a place with a good view of the northern horizon with no tall buildings or trees in that direction. You do not have to leave the city to do this exercise but you should get away from bright lights if you can. You will not be able to see ANY stars from a brightly lit parking lot. But even in the parking lot you may be able to find a corner where there are not too many lights to the north of you and you can make out the big dipper. Use common sense with regard to your personal safety. Don’t go someplace unsafe. Central Park at midnight is probably not a good place to do your homework!It’s wise to take someone else with you.
Take a flashlight, spare batteries, plenty of warm clothes, a couple of pencils and a clipboard to hold your paper.
Locate the big dipper. Remember the real sky is MUCH bigger than the computer screen.
Face north and look at your drawings for approximately this time of day. You should have a fairly good idea of the orientation of the big dipper. If the dipper is very low in the sky at this time it may be hard to find. You may have to wait a few hours until it gets higher in the sky.
Sketch it as you have on the previous problems.
Record the date and time.
Problem 9 Repeat the process in Step 8 at least two hours later than your observation time in Step 8 (record your day and exact time). The same night is preferred OR it can be at least within 7 days.
Estimating the Altitude of Polaris
To measure altitude, simply use your fists. Start by holding one fist out in front of you with your arm fully stretched out like you are holding a vertical rope, and your arm and body making a 90 degree angle. This allows for the bottom of your fist to be “sitting” on the horizon in front of you. (From top to bottom, a fist at arm’s length is about ten degrees on the sky.) Start climbing this imaginary rope with one fist over another, touching. Count the number of “fists” from the horizon up to the star/moon/object you are interested in. So, if you counted 5 fists then your altitude would be 50 degrees, 6.5 fists would be 65 degrees, etc. If the horizon involves trees, buildings or a mountain, estimate where the horizon would actually be if there were no trees, mountains or buildings and use that as the starting point for your measurement. It will be important that you are able to measure the altitude within one fist (~10 degrees).
Submit your data sheets to the proper Dropbox (using digital camera or scanner) then proceed to the: “What did you see? (Big Dipper Stellarium Activity/Discussion)” Discussion
Big_Dipper_Stellarium_Activity.docx_final.docx Big_Dipper_Stellarium_Activity_Data_Sheet_download.rtf Big_dipper_and_cause_stellarium.docx