Measuring the Motion of a CME Using NIH Image
These are instructions for measuring the velocity and
acceleration of a CME using NIH Image software. Read the Motion of a CME Lesson Plan first.
- To demonstrate the ability to use image software from the net.
- To demonstrate the capability of moving data from one program to
- A computer with the specifications needed to run NIH Image.
- A copy of NIH
Image on the computer.
- Software on the computer to create
- Software in the computer to create reports. (optional)
LASCO images of a CME.
(If you do not know the procedure for bringing down an image off of
web page, go to "Procedure: Bringing down an image.")
- Go to the CME LASCO image on the SOHO pages at
- Click and hold on the first image. A window will open. Move the
cursor to Save this image as... and release. Save this image
in a place on your computer that you will be able to access easily.
It would also be a good idea to name the image just in case you will
need to search for it.
B. The Activity
Make sure that you have NIH Image in your computer as well as a
spreadsheet program. If you are working with students, it would be
good idea to have a program such as Lotus 1-2-3 or ClarisWorks
will allow the students to print reports using different programs.
These programs have spreadsheets as well as word processing
that will allow easy transfer from one type to another.
- Open NIH Image.
- Go to the ANALYZE menu and pull down to OPTIONS. You will get
- Use NIH image to calculate the scale of the image:
- a. Click the boxes for AREA and PERIMETER/LENGTH. Click OK.
- b. Using FILE from the pull-down menu, select OPEN.
- c. Open the first LASCO image of the CME that you down-loaded from
the SOHO web-site. (NOTE: The image must be in PICT or GIF format.
This may mean opening the image with a translator program and then
saving it under one of these formats)
- d. Note that at the bottom of the image there are white tick marks.
These marks show the diameter of the Sun. It is possible to print
this image and do the work by hand. Select the measuring tool and
starting from the center of one white tick mark click and drag to the
center of the next tick mark. (if you hold the shift key down it will
automatically draw a straight line)
- e. Go to ANALYZE and then to SET SCALE. The following window will
- f. The measured distance is in pixels as seen by the units. If you
click on PIXELS next to UNITS you can choose the units you wish. We
would suggest that you choose kilometers.
- g. In the KNOWN DISTANCE box (that should be highlighted) type in
diameter of the Sun in kilometers. This distance is 1,392.000.
- Measure the location and area of the CME
- a. Move the cursor (measuring tool) to the edge of the occulted area
and draw a line to the edge of the CME.
- b. Go to ANALYZE then MEASURE. When you release the mouse on
MEASURE it will automatically measure and scale the distance along
that line. It will also measure the area of the line. This can be
- c. Next go to OPTIONS then THRESHOLD. The color of the screen will
change and the LUT (Look Up Table on the side) will change to black
and white. Your cursor will also change to a "+". By moving the
black bar along the LUT you can change the color of the pixels to
black. You will notice that at one point the CME will be white while
all of the background will be black.
- d. Chose the wand tool (it looks just like a magic wand) and click
along the outside edge of the CME until "dancing ants" surround the
- e. Go to ANALYZE then MEASURE.
- f. Open the next image and redo steps 10 through 14.
- g. Once all of the images have been processed, go to ANALYZE then
When you go to ANALYZE and SHOW RESULTS you will see a screen like
the one to the right.
The first number is the area of
the line and the second is the distance along the line. Remember that
the first measurement you took was the length of the line and the
second was the area of the expanding gas. We therefore do not need
the first area and the second length. As stated before, we will
change this later. Note that your numbers will not be the same as
- h. Go to FILE then SAVE AS. Select MEASUREMENT from the buttons
- Transfer data to a spreadsheet program
- a. Open the above file with a word processing program. Go to
then COPY MEASUREMENTS.
- b. Open your spreadsheet program and paste the results of the
measurements. This is where you will have to delete the
that you don't need. (see step 16).
- c. Using the instructions for your spreadsheet program, make a table
that will show velocity and acceleration of the CME away from the Sun
as well as the change in the area of the CME.
Return to the Motion of a CME Lesson
Created by: Dennis Christopher
Direct Comments to:
Last modification: Friday, 09-Nov-2007 11:33:35 EST