Youth AstroNet Program Color This presentation based on information and materials from The Harvard-Smithsonian Center for Astrophysics Science Education Portal http://waps.cfa.harvard.edu/eduportal/ Questions about this presentation? Contact Carolyn Donelan @ Carolyn.donelan@richlandone.org

We see colors that are reflected or emitted. Image credit: http://astronomybarajas.weebly.com/uploads/1/3/4/2/13425894/4839083.gif Image credit: http://rumneymarshart.weebly.com/

Primary and Secondary Colors Image credit: http://www.photographyknowhow.com/images/coloroflight1.gif

Filters Filters absorb some colors and let other colors pass through. Image credit: http://www.education.com/science-fair/article/colored-lights-effect/

Filters with a CCD Even though our CCD can only “see” black and white, if we use filters, we can assign the appropriate color to the image. Image credit: http://www.outbackphoto.com/dp_essentials/dp_essentials_03/color%20filters-4.gif

RGB Images If we layer our RGB images, then we can get a true color image. Image credit: https://cdn.tutsplus.com/active/uploads/legacy/tuts/076_rgbShift/Tutorial/1.jpg

So to make a true color image with the MicroObservatory telescopes, we’ll need three pictures of the same object, taken with three different filters. RGB Images Image credit: http://www.sci.utah.edu/~acoste/uou/Image/project1/images/RGB_image.png

How to Process an Image Go to microobservatory.org

Scroll down…Click on YouthAstroNet Portal

Click on YouthAstroNet Activity Portal

Login?

You should be here:

Scroll down… click on MicroObservatory Robotic Tools

Click on Use the images in JS9

Hover on Archived Images On the menu that appears, click on the first M42-OrionNeb (this is the Orion Nebula)

Your image should look like this… Hover over Image and click on display FITS header.

FITS Header The FITS Header contains data about the image… where the telescope was aimed, what the exposure time was, and what kind of filter was used.

Filter Scroll down until you find the FILTER information. This image was taken with a RED filter. Close the FITS Header (click Close at top of window).

Red Hover over Color and click on red. Now, adjust the scale, brightness limits, stretch/contrast, and shift/bias.

Save as FITS When you have your image the way you want it, save it as a FITS image. Include RED in the file name. (Hover over Image and click on save as FITS image

Process the second Orion Nebula image Archived Images M42-OrionNeb Look at the FITS header and change the image to the appropriate color. Adjust Brightness Limits, Stretch/Contrast, and Shift/Bias. Save image as FITS with GREEN in the file name.

Process the third Orion Nebula image Archived Images M42-OrionNeb Look at the FITS header and change the image to the appropriate color. Adjust Brightness Limits, Stretch/Contrast, and Shift/Bias. Save image as FITS with BLUE in the file name.

Making a Composite Hover over My List. It will list all the image files you currently have open. Close all of your files EXCEPT for the THREE Orion Nebula files. Hover over Color and click on RGB mode. This will layer all three pictures on top of each other. Since the pictures were taken at different times, we need to shift the pictures, so the line up with each other.

RGB Mode Right now, the “blue” image is “on top”. Hover over Zoom and then click on shift. Shift the image a little down and to the left, so the blue and red stars line up on top of each other.

RGB Mode Hover over Image and click on an image name until the green image is “on top”. Now shift so the green stars align with the red stars.

RGB Mode Does another color still need aligning? Select that image and shift the image until the image is how you’d like it to be. When you are done, save it as a PNG file. Don’t forget you can zoom and add text…

Ta da! A true-color picture of the Orion Nebula!

Why do some stars appear brighter? Luminosity is how much light the star emits from its surface. Apparent brightness is how bright the star appears to us on Earth. A very luminous star might appear faint because it is very far away. Image credit: https://commons.wikimedia.org/wiki/File:Inverse_square_law.svg Image credit: http://www.cv.nrao.edu/~rdickman/images/dipper_depth.jpg