Astro-Image | Barred Spiral NGC 1300

Spiral galaxies are common in the universe. This example of the Pinwheel Galaxy M101 from the Hubble Telescope is found in Ursa Major, the Big Dipper.

Hubble Space Telescope | M101

About ⅔ of the spiral galaxies also have a feature in the center called a bar. This next example, also from Hubble, is known as NGC 1300. Some bars are very long and pronounced, as this one. Other galaxies have a bar that is quite short.

Hubble Space Telescope | NGC 1300

Notice in each galaxy the blue cast in the spiral arms. It comes from the glow of relatively young stars. Older stars tend to glow white, yellow, or orange. The vein-like structures are regions darkened by the absorption of dust.

I like to download greyscale images from the Hubble Legacy Archive site and try to combine them into color images. Hubble and other astro-imaging systems collect images in greyscale with their detectors. Filters of various wavelengths are placed in the light path. By using red-filtered, green-filtered, and blue-filtered images, they can be combined into an RGB color composite such as those above.

After selecting and downloading the 3 greyscale images, I open each in an app called FITS Liberator v4. Contrast and brightness are adjusted. The images are then saved as tif files labeled red, green, and blue. Next, the 3 tif images are opened in Photoshop Elements. Each greyscale is colorized into red, green, and blue versions. The green image is copy and pasted as a layer onto the red layer. The Blending Mode for the green layer is set to Screen so the green and red layers mix their colors. The blue image is copy and pasted as a layer onto the green layer with Blending set to Screen. Some adjustment might be needed to align the stars in the 3 layers.

My attempt for NGC 1300 is below. My choices of contrast and brightness for each greyscale image affects the final outcome of the colors of the RGB version. The Hubble images I chose were of the right half of the galaxy.

More examples of my attempts can be found here.

15 thoughts on “Astro-Image | Barred Spiral NGC 1300

  1. Every time I see interstellar images like this, I am truly star struck. I have flashbacks to Philosophy 101 and the first question: Why is there something vs. nothing?

  2. Hi Jim, I thought of a question for you just today. Does the moon rotate around the earth at the equator or on a different eclipses? I was thinking about how the rise and set points on the east/western horizon varies between solstices, which I realize is due to the tilt of the earth towards/away from the sun, but also the moonrises move northeast and southeast as well. Only on the equinoxes do both sun and moon follow a similar path. Curious minds need to know!

    • Good question. If the Moon orbited Earth directly above the equator, it would rise and set at the same places on the horizon throughout time. Instead, the Moon’s orbit is tilted with respect to the equator by about 5˚ causing it to rise and set at varying points on the horizon throughout time. Both the Sun and Moon vary their rise/set points giving those patterns you notice. You are observant.

  3. Very informative post! I looked up the Liberator software. I am looking forward to images from the James Webb Telescope. It will capture images in infrared. You will be able to assign colours to colours not visible to the eye. Take care. Bob

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