Methodology
Obtaining JWST Images
The Mikulski Archive for Space Telescopes (MAST) is a premier data archive for space-based astronomical observations. It hosts a wide array of data from JWST, the Hubble Space Telescope, and other missions, making it a crucial resource for exploring the universe.
Explore the universe with the MAST Portal. Whether for research, education, or curiosity, MAST offers the data and tools you need to reach for the stars.
You can visit the MAST portal For more details on how to obtain images for specific galaxies, nebulae, etc.
Raw Images
The JWST captures detailed images of the universe. These raw images, available on the MAST Portal, provide valuable data for exploration and analysis.
When the target name is inserted MAST portal will then list all the raw data captured by various telescope it contains. The data can then be filtered out by type of data, mission(which space telescope), date, etc. These raw images comes in different filter as it captures different details of the celestial object each providing crucial information regarding the object.
Pre-processing Raw Images
The downloaded raw images can then be processed using suitable image processing software such as SIRIL, FITS Liberator, Photoshop and/or GIMP. First the raw images needed to be stretched as it is captured in the wavelength of light invisible to the naked eyes. this stretching processed literally stretched the brightness intensity so that the images will start to reveal the intricate details hidden within. and such process can be achieved through SIRIL or FITS liberator.
Processing Raw Images
The stretched raw images then can be saved in 'TIF' file format so that it can be accessed using the image processing software that we about to use. Both Photoshop and GIMP provide the same functions and the same end result can be achieved either way. the purpose of these software are mainly to stack the multiple raw images into single file and at the same time assigned colors to each of the filter image so that the final stacked image will contain all the colors that would help radiate the vibrance and contrast of the celestial object.
With the 'colorize' function colors can be assigned through the hue value onto the raw images according to its filter. With enough raw images stacked on top each others representing different hue value, a vibrant and mesmerizing image can be obtained.
JWST Filters
Filter sets are specific ranges of wavelengths that the telescope’s instruments can isolate and capture. Each filter allows only certain wavelengths of light to pass through, effectively capturing images at specific parts of the electromagnetic spectrum. This helps in analyzing different aspects of astronomical objects, such as their temperature, composition, and structure.
The filter names follow a specific convention: "Fnnnx" where "nnn" refers to the central wavelength (e.g., 200 for 2.00 μm) and "x" indicates the filter width (W for wide, M for medium, and N for narrow).
1. Narrow Band Filters: These filters have a small range of wavelengths, typically focusing on specific spectral lines. They are used for detailed studies of particular features, such as emission lines from certain elements.
2. Medium Band Filters: These filters cover a broader range of wavelengths than narrow band filters but are still more selective than wide band filters. They offer a balance between specificity and broader wavelength coverage, useful for observing specific regions of the spectrum while capturing more detail than narrow bands.
3. Wide Band Filters: These filters allow a broad range of wavelengths to pass through, making them ideal for general imaging and surveys. They are used when a broad view of an object or area is needed, capturing a wide range of wavelengths in a single observation.
These classifications help scientists select the appropriate filter based on the specific needs of their observations, whether it’s detailed analysis of certain spectral features or broad imaging of celestial objects.
Colour Mapping
Raw images captured by the JWST are originally in grayscale, representing the intensity of light at specific wavelengths. To create the stunning, colorful images we often see, scientists assign colors to these grayscale images based on the filters used during the observation. This process helps visualize the data in a way that highlights different features and makes the images more interpretable.
Colors are assigned to each grayscale image according to its filter. Typically, shorter wavelengths are mapped to blue, mid-range wavelengths to green, and longer wavelengths to red as shown on the figure above in the NIRCam Filters.
Color mapping is the process explained previously where we change the hue value for the raw image in the image processing software so that the grayscale image can be converted into a colored image.
Final Image
The colored images from different filters are then combined to form a single composite image.This composite image can show a full spectrum of colors, representing the different wavelengths captured by the telescope.
As multiple raw images uploaded into Photoshop/GIMP the opacity of each image are adjusted to be somewhere around 50% so that the details and color of each image seeps through each other forming the final image.
