Science

Here’s how to edit James Webb Space Telescope images

Want to play with telescope images in your spare time?

There is a large community of people using images from the James Webb Space Telescope to create breathtaking images. Among them is Judy Schmidt, who recently created an impressive image of the Phantom Galaxy (M74) based on Webb data.

Schmidt met with Space.com to show the basics of how to convert raw data into an image using free software as well as standard imaging software such as Adobe Photoshop. Schmidt has 10 years of experience, but he says anyone with an interest can make beautiful images with a little experimentation and enthusiasm.

You can view more impressive images of Webb’s photographs and other space objects on Schmidt’s Flickr page. (will open in a new tab). Many of the concepts discussed below are available in her 2017 YouTube Image Guide. (will open in a new tab).

Related: Stunning James Webb Space Telescope image shows stars forming in strange wheel-shaped galaxy
Gallery: First photos of the James Webb Space Telescope

Judy Schmidt headshot

Amateur astronomical image processor

Judy Schmidt has been processing amateur astronomical images for ten years. She received her degree in Graphic Design and Multimedia from OSU-Okmulgee in 2003 and currently resides in Modesto, California with her son, cat and husband.

Space.com: For those who are not familiar with this, where can I even look for these images? Where are raw images stored?

Schmidt: It’s part of the MAST archives. (will open in a new tab) [the Barbara A. Mikulski Archive for Space Telescopes.] Assuming we’re looking for the Phantom Galaxy, its correct name is M74. We will simply enter the name of this galaxy into the MAST search bar, as if you were using Google. I usually prefer to use the advanced search because it’s easier for me to filter out a lot of things.

[Editor’s note: Look at the left-hand side of the MAST archives webpage for the advanced search parameters.]
  • Check the box in the Mission section labeled JWST.
  • We need to avoid yellow and orange results. Yellow is data you cannot access and orange is scheduled observations. To filter them out, scroll down to “Data Rights” and select “Public”.
  • Another very useful thing is “Calibration level”. This is the “wrongness” of the data. Select calibration level 3 to get images that have been aligned and aligned.
  • Also remember to select “images” so we’re looking at images and not spectra.

Images of NGC 628 taken by the James Webb Space Telescope. "ghost galaxy") shows glowing dust in this citizen science image.

Glowing dust is visible in an image of NGC 628 (Ghost Galaxy) taken by the James Webb Space Telescope. (Image credit: NASA/ESA/CSA/Judy Schmidt)

Schmidt: Once you’ve done that, I’ll explain the filters as quickly as I can. The image information has a column labeled “Filters”. This is a piece of metadata showing through which filter the telescope looked at the object. For example, you can see on MIRI [mid-infrared instrument] page (will open in a new tab) that F770 is 7.7 µm. In this example, 770 is the shortest wavelength at which these observations were made. This is important to know because you want the shorter wavelengths to be more blue in your color image.

Space.com: It would be natural if you used your eyes, right? Because red wavelengths are longer and blue ones are shorter, right? Though obviously we’re using an infrared telescope, so it’s not going to be completely analogous.

Schmidt: Yep. Infra-red filters, despite being broadband, different filters seem to contain different narrow emission lines.

Space.com: In general, the key to success will be to use multiple filters for different wavelengths. You want longer ones, you want shorter ones. How much, at least, is good for work? Two three?

Schmidt: I download them all and puzzle over them until they look right. Once you’ve selected your image, click “show filter” and you’ll see a thumbnail. With this M74 filter I don’t know exactly what I’m looking at yet because it’s so small but looks amazing. If you want to take a closer look, you can click on the magnifying glass and the image will download to your computer.

The James Webb Space Telescope in 2020.

Most of the James Webb Space Telescope dataset is available online free of charge in the MAST archive. (Image credit: NASA/Chris Gunn)

Space.com: Once you’ve chosen your dataset, how do you go about working with it?

Schmidt: You click on “Add Data Products to Download Cart”. Try not to download everything you see first. Right now I see over 1000 files. I would recommend that you choose I2D, a corrected 2D image. This is a FITS file that seems fairly familiar to anyone involved in astronomy. The FITS file is compressed into a ZIP file.

Open the ZIP file with FITS Liberator. (will open in a new tab). It’s free and available from ESA. [the European Space Agency] to get people like me, and hopefully more hobbyists, into image processing. Images often have ultra-high dynamic range, and we have to adjust it so that we actually see something. My favorite is to use the stretch function called ArcSinh. [Editor’s note: Consult the FITS user guide (opens in new tab) for more information on all functions.]

Space.com: What does this feature do?

Schmidt: It takes an image from a line display and basically applies a curve to that line so that the darkest parts of the image get brighter and then the brighter parts of the image remain. Find the histogram in this function. This will tell you where most of the pixels are in terms of brightness. On the right is the brightest part of the image, and on the left is the darkest. You want to move the hill to the middle of the screen. When we do this, we end up with a cute little mound instead of an angry spiked mound.

Space.com: Now I can actually see the details of the image. Not everything is black.

infrared image of jupiter

Judy Schmidt recently created this image of Jupiter from data from the James Webb Space Telescope. (Image credit: NASA/ESA/CSA/Judy Schmidt)

Schmidt: Now save it as a 16-bit file. (32-bit is overkill, 8-bit is pixelation.) When you do this, make sure you always have the upside down image selected. Otherwise, you will get a view from a telescope that has mirrors. I save it in TIFF format, which is a very common file format. Then I apply what is called an adjustment layer. (will open in a new tab) in photoshop. [Editor’s note: Consult the Adobe Photoshop user guide (opens in new tab) for more information.]

What’s great about an adjustment layer is that you can move back and forth while editing. You don’t actually touch the pixels, which is called non-destructive editing of the image. This is what I love to do. I like to keep the original in its original state so that if I screw up I can go back and fix it.

As I said before, I recommend downloading as many filters as possible, studying each one carefully, and then making a decision. This is what I do.

Next, you’ll have a grayscale image, so we’re going to convert it to a standard RGB image. [red, green, blue] image. I put my single filter in a group along with everything I change, like curves. I’m just like the file system. I can change everything in this group and then tell Photoshop that I want this group to occupy only the red channel. This makes a very simple color image.

Advanced tricks from here:

  • Go to Advanced Blending (will open in a new tab) box. This is my way of dividing the filters into channels, for example setting one to take only red and the other only blue.
  • If there is nothing in the green, I can add another filter or create what I call a “pseudo green channel”. Essentially, the pseudo green is created using the channel mixer. (will open in a new tab). He takes half red and half blue and puts those halves into the green channel.
  • Make sure your RGB channels add up to 100 percent or as close to that as possible.

Space.com: If you ever get stuck on how to manipulate an image, what steps would you take to get yourself help?

Schmidt: I have no one to ask. There is no one. I just have to figure it out myself.

Space.com: So you’re diving into Photoshop’s settings. You are browsing the MAST website. You also look at the MIRI filter website that you showed me, along with any other tools of course, and then take it from there.

Schmidt: It’s definitely a mystery. But I’ve been doing it for 10 years now, so it’s almost automatic for me.

This interview has been edited and condensed.

Follow Elizabeth Howell on Twitter @howellspace (will open in a new tab). Follow us on Twitter @Spacedotcom (will open in a new tab) or on facebook (will open in a new tab).

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