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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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.
ReplyDeleteI am using windows 7 and I dragged and dropped plugin in Image J. I have seen tools and employed RGB plugin. However, I have to do it when I restart Image J.
ReplyDeleteI could not figure out a way to save Image J with the plugin.
Second problem I faced was with the alignment.
One of my sample was a little bit off and I had to align it. However, it was a little bit confusing to find out which one was off. I compared a star`s DN values; it kinda worked. Since I magnified in order to exactly match them, the star that I took as reference was bigger and it was difficult to tell the reference point.
I am using a MacBook. The macros had to be install using the Plugin ->Macro -> Install command. I tried adding the text to the startup file for ImageJ but got only two icons on the menu bar. I worked to two image files M5 and M16. M5 was simple to adjust. M16 was more difficult to adjust. On my first try, the image contain just a few star looking objects. I then looked under google images of M16. I noticed a hazy area. I redid the M16 file but spent more time adjusting the images. Once I adjusted min and max, then I slowly moved the brightness. This brought out the haze on the r and v filter images. The b image could not be adjusted to show the haze. I downloaded four images from each of the categories. I want to know how you can tell the difference between star clusters and nebula. M16 ended up with a greenish ting in order to see the haze. M5 just appeared like tiny stars of red, blue and white. I did have to align M5 and M16 appeared ok.
ReplyDeleteI downloaded the M17 nebula images as I thought they would represent an object with a broad spectrum. Unfortunately, because it is an emission nebula most of the radiation is at the red end of the spectrum. I then attempted processing them by hand. The difficulty here is that the histogram in the B&C function does not allow you to expand the brightness axis (x-axis), so one is trying to make adjustments on a narrow spike of data. So, at the end of it all, I used the “auto” feature, which provided a much better image than what I could create manually. Then when I went to save the processed images under new names, and tried reopening them, none of my processing had been saved. As a result I only got to this one image. I will work on another image or two over the next couple of days.
ReplyDeleteComposing the RGB image was somewhat easier, as long as the images remained open - refer to the problem above. The problem with the RGB Composer is that the arrow keys don’t really tell you what is going on, as there is no slider bar to tell you where you are at within the spectral range (R, G or B). On my old Mac laptop the image update is so slow that it was taking too long to see what the results were for any given change. Again I used the “auto” buttons to come up with a satisfying image. The alignment was almost dead-on from the start, I played around with it just to see what the align buttons did.