M31 Mosaic - Eight frames of the Great Andromeda Galaxy
Location: Taken remotely from Grapevine, Texas using the Conley Observatory at the Comanache Springs Astronomy Campus near Crowell, Texas
Temperature: 90 - 92 degrees F
Date: August 2019
Scope: 12.5" RCOS Ritchey-Chretien
Mount: Software Bisque Paramount ME
Cameras: FLI Proline PL-16803 astronomy camera and Nikon D810a (for a small amount of color.
Exposure Info: Eight frame LRGB mosaic for the grayscale data, taken with the PL-16803 unbinned. Approximately 16 hours total luminance. Color data taken mostly in 5 RGB frames covering the galaxy disk, each frame averaging 2.5 hours for approximately 12.5 hours of total RGB color. A small part of color was borrowed from Nikon D810a image of taken last year (36 minutes using a small Tak FSQ-85ED apo refractor).
Total Exposure Time: Just over 29 hours!
Processing of Grayscale Frames: Calibration, star alignment, and integration of individual frames done within PixInsight. Each frame received Multiscale Linear Transform, Dynamic Crop, Histogram Transform, Local Histogram Enhancement, and HDR Multiscale Transform in PixInsight. Grayscale frames assembled in PixInsight using Gradient Merge Mosaic process. Noise reduction and local contrast enhancement performed in Photoshop CC (using ProDigital Actions) on the full mosaic grayscale frame.
Processing of Color Frames: Calibration, star alignment, and integration of individual frames done within PixInsight. Each frame received Multiscale Linear Transform, Dynamic Crop, and Histogram Transform in PixInsight. Color frame brought into Photoshop CC and aligned , frame by frame, with the grayscale master frame. Color frames were balanced, heavily saturated, cleaned of noise (a variety of techniques), and blended with luminance data using Color blending mode. Additional color for background stars (those not covered by the mosaic frames) was added within Photoshop CC using the Nikon D810a image taken last year.
About this Image...
Shooting a mosaic, especially an 8-frame color LRGB image, is not for the faint of heart! But every now and then we astrophotographers get the urge to push our skills and our equipment. The result of such mosaics, like this one of the very familiar M31, Andromeda Galaxy, is to achieve fine resolution (detail) as delivered by the long focal length optics WITH the wide field of view typically given by shorter focal length scopes and lenses.
Meaning? A huge galaxy such as Messier 31, Andromeda’s catalog designation, can be captured completely, yet in terrific detail.
This galaxy (found within the constellation Andromeda) isn’t the closest galaxy to us, but it’s pretty close...only 2.5 million light years away. That’s 1.47 x 10^19 miles, if you need that perspective. As pictured, you could fit 7 or 8 or our moons across the disk of this galaxy from our sky perspective. It’s huge and it’s a naked eye object in most rural-to-suburban skies.
Oh, BTW, any star that you see in this image (click on it to see the full resolution image) is in our own Milky Way galaxy, since we have to look through our own neighborhood to see the next. Stars in Andromeda are too small to see from this distance, though you can witness clusters of them together, especially all the globulars that have their own set of designations.
How many stars are there in Andromeda? Well, you are staring at about 1 trillion stars, give or take a couple. That is about 4 or 5 times the number within our own galaxy.
One of the more intriguing aspects of M31 is that the light captured here first left that galaxy around 2.5 million years ago. In other words, looking into the sky is about as close to actual time travel as we can experience.