Sunday, January 30, 2011
Module 7
In this exercise, you will use imageJ with an astronomy plugin to create color (RGB) composite images. You will have to download the plugin and place files into your imagej program file. You will make color composite images using each image set. Send the images to martinbrockie@gmail.com. On the blog discuss how you constructed the images; adjusting, color combining and aligning.
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ReplyDeleteThis was another 'fun' one. I struggled at first because I hadn't updated my ImageJ program. But, once I did this (From Help Pull Down Menu - Select Update Image J) it worked just like Chris said it would.
ReplyDeleteAdjusting the image to show stars/nebulae and then adjusting the contrast gives striking images of these heavenly bodies.
Once into the RGB composer the images can be nudged to match-up and produce a single true image. Some of the color shows through more than others - for example, my Eagle nebula appears red - which must mean that the wavelength of light emmitting from this particular nebula is mostly near the 656 nm.
So we can use these as astronomers do, we can teach our students about these color images and 'know' a bit more about how they are made and what they mean.
I really enjoyed putting these images together. I chose one of the galaxies and one of the globular clusters. (On imageJ, my new icons didn't show up at first so I just went to Plugins, Install and selected the new tool from a file, and then the new icons showed up).
ReplyDeleteI had to align the images for each set first. On my first try, I didn't adjust the original contrast correctly (before the RGB) and ended up with a dissapointing final image. But when I started over and got the inital brightness and contrast optimal, it turned out much better. My main problem is not knowing how these pictures should look. For example, I could make the color of the galaxy on the red side or on the green side--I went with what looked best. I guess I could try to look up the real images and compare ...
When you have constructed your RGB image, send me a screen shot including the plugin RGB tools. It is important to always assign Blue to the shortest wavelength image and Red to the longest wavelength image. You can use the new images from WISE (wide infrared survey explorer). Find instructions and my students' work at howenstinescience.pbworks.com/. The plugin copes with the fits images when working on a mac, but using the old pcs at school, my students found that they needs to convert the fits images to jpeg before using the plugin.
ReplyDeleteThe first time I completed this assignment, I didn't end up with much of an image. Then, I realized the obvious: zoom in!
ReplyDeleteI had a similar problem to Josie, where I wasn't sure if my image looked the way it was supposed to. So, I looked it up online to compare to actual images. The images of the Cat's Eye Nebula were much more impressive than my final product, but I assumed that this was because of skill using image processing software.
Aligning the composite image was very cool. It was neat to see the different colors move and merge into one image. I was concerned that my brightness/contrast was not as good as it could have been (I wasn't sure how they were supposed to look!), but I think it didn't end up mattering in the end. Was the brightness/contrast just so we could see the image in the beginning?
This one I found very frustrating, because I really have no idea if I'm doing it correctly (needs experience, but no real instructions, is not very helpful!). But I installed the plugin without issue, used the Auto setting as much as possible to help with the adjustments, and winged it as well as I could!
ReplyDeleteI always regret putting these assignments off until all my other responsibilities are met. No more than tonight when I glued myself to the TV to listen to tonight's newsworthy events.
ReplyDeleteI was able to download the plug ins. The first image set that I tried, I didn't get very good results (I assume as I don't know what it was supposed to look like). I scrapped that one and tried three others. One of the things that I noticed was when I merged the images, I looked at which images it put where. They seemed to be in the order that they appeared in the folder so I had to change it to make the red correspond with red, etc. On the last image I tried, I paid more attention to the graphic at the top and made sure that the "straight line" and the "steep jagged line" were aligned at the bottom at the x axis. That seemed to help.
I was happy to have this activity to do this evening as I am thinking too much about the fact that my 18 year old son is flying internationally (back to Tucson) tomorrow. I assume, however, with tonight's events, airport security will be high.
Hi there,
ReplyDeleteI did my course last fall 2010 and never tried to do this module 7. This is actually a very nice activity.
I spent all night just to figure out how to insert RGB composer on my plugins. I deleted my old imagej then installed another one.
I updated my imagej then finally I got the image.
I played with the brightness and contrast and ups and downs.
The program will select the images to be the RGB ones, and they may or may not be the ones you actually want to use. Clicking on the top menu in each color will allow you to select the correct image to use for each color. The red filter and visual filter are obvious. Using the clear, nebula, and infrared filters gives us a choice for "blue." After making the file selection, I click on >Update. The >Auto button will change the brightness and contrast. You can then work with the rest of the buttons to modify brightness, contrast, and upper and lower limit value ranges. Most convenient, however, are the direction buttons that let you align the stacked images
I believe the main used of the RGB composer is to bring the three images together so that they match, not produce bizzare image effects -
A bit of practice with simple images will help me to appreciate the use of this in dealing with more difficult astronomical images
Boy, you can really spend a lot of time on this! I spent over an hour tweaking things for my globular star cluster, and another half hour playing with the Ring Nebula. It was fun, and it gave me an appreciation of how those pretty composite images are made.
ReplyDeleteMy school is having graduation next week so I will have to try this out next year with my students, but ImageJ continues to fascinate. I need to read through the documentation.
Installing the plugin was a real challenge. I tried a million things on my school pc, and also all the suggestions posted here, but nothing worked. I was able to install it on my netbook at home. That is something I need to look into further before using it with the kids at school. The school lab is Mac so maybe I will have better luck with the plugins there.
My question is, how can I help my students to ask questions that will lead to using ImageJ to investigate?
The first image I tried was M57, which is an interesting ring-shaped planetary nebula. Different image filters required very different
ReplyDeleteminimum and maximum values to bring out the nebula, which makes sense. It's a pretty little object, a lovely ring spreading out from a central point. I was able to merge all the images together to be one and I admit that I don't see a lot of change or new information,
although it does make the picture a little bit more visually appealing. When I used the auto-adjust function under brightness and
contrast I got a very clear image which is very, very, very red...so much so that I wonder if I went astray with something about my
technique.
The second object I choose to analyze was m102, a galaxy. I took the images and put them together and then dragged the red, green, and
blue colors apart from each other. This taught me that the background stars are all bright in red, green, and blue but that the galaxy
itself appears to only be bright in green and red and is rather dim in blue relative to other objects. I suppose this makes sense seeing as
how many stars emit more brightly in red or green than blue. Also might the galaxy be dim in blue because it is distant and heavily redshifted relative to the stars in the foreground?