RGB-Composite with JS9 (AiM)


  • If you have your own RGB images, activate it in its directory and drag it onto the JS9 interface. (drag and drop)
    (Alternatively, you can load the images via the menu File ➔ open local ….)

    If you don't have your own R G B-images, you can load some of Messier 1 (short: M1) here for practice:

    M1 taken with red filter     :    M1 (red)
    M1 taken with green filter :    M1 (green)
    M1 taken with blue filter   :    M1 (blue)

  • Switch between the images using the menu File ➔ Images.

  • If you carefully drag the left mouse button over the individual images, brightness (left-right) and contrast (up-down) can be sharpened.

  • A suitable color can be assigned to each image with the Color menu.

  • Activate the RGB mode via the menu Color ➔ rgb mode.

  • If the fixed stars of the individual images are not exactly on top of each other, you can use the blue arrow keys to move them to the correct position.
    (Each click is a pixel. Depending on the speed of the computer, the reaction may take some time.)

  • Save image using menu: File ➔ save … ➔ PNG .

       Your Job: Copy your colored picture of Messier 1 into a word processor and create a profile of this astronomical object.
Research everything that is known about this object on the internet.

Alternatively, you can edit an online profile here: Astronomical Profile .

on working
with JS9:
1.) If you get lost while experimenting with JS9 or nothing works anymore, just refresh this page.
2.) In addition to the image data, all scientific recording parameters (filter used, exposure time, exact recording date, etc.) are stored in FITS files.
This data can be viewed in the FITS header:
Menu: File ➔ display ... ➔ FITS header
3.) If you would like the editing window to be larger or smaller, you can use the small triangle (bottom right) and hold down the left mouse button to set this.
Since only screenshots can be saved with JS9, it makes sense to enlarge the editing window before saving.
A larger editing window can also be helpful for the exact alignment of the fixed stars.
4.) When aligning the fixed stars, zooming with the Zoom menu can also help.
With the menu Zoom ➔ zoom to fit, the image is readjusted to the editing window.
5.) The View ➔ Blending menu opens a window that displays all loaded images.
This can provide a better overview. In addition, as an alternative to the Color ➔ rgb mode menu, you can overlay any number of images.
(See example "Dumbbell Nebula-M27" below.)

More practical examples:

The JS9 application was developed by CENTER FOR ASTROPHYSICS|HARVARD AND SMITHSONIAN and didactically reduced by us: https://js9.si.edu
The program is subject to the MIT license. Source code @GitHub
Astronomy and internet in Münster (AiM): http://www.aim-muenster.de