DID YOU KNOW...?
Our Moon has far more color than its typical black and white portrayal in media.
Continue on for proof and an explanation of my image, including the processing and acquisition of the image.
Image Acquisition and Processing
First, I must first acknowledge some difficulties I ran into. Originally, I attempted to use PROMPT-MO-1 to take these images but the telescope was recently down for maintenance and did not have updated bias and flat pictures which lead me to originally create an image with very unnatural colors and flaws. I had to recover PROMPT-5 image data from another student, James B.
I took this mosaic image of the Moon remotely using the telescope PROMPT-5 through Skynet. PROMPT-5 cannot capture the whole Moon in one shot, so I opted to use a 5 x 5 grid dithering pattern to ensure the entirety of the moon was captured. In order to accentuate the true colors of the Moon I took exposures using three filters. The filters, exposure numbers, and exposure times are listed in the table below.
Filter Name | Exposure # | Exposure Time (sec) |
U | 25 | 0.2 |
Halpha | 25 | 0.2 |
OIII | 25 | 0.2 |
My Moon images were all processed in Afterglow. I had 75 exposures total, however a few exposures failed so I had to use a few "patches" of archival data to ensure I got a comprehensive stacking job. The first step I took was aligning the images. Using the aligner tool menu in Afterglow, I enabled Mosaic Mode and disabled Rotation, Scale, and Skew. I chose to use the formula AKAZE with a radio threshold of 0.4
After successfully aligning my images, it was time to stack them into three separate mosaics --- one for each respective filter I used. I made a U stack, a Halpha stack, and an OIII stack. For all three mosaic stacks I chose to use an equalization order of 0. I grouped my three stacks together. Below are the respective stacks. I colored Halpha red, OIII green, and U blue.
I opted to change my color balance method from linear to midtone to bring out the detail in both the faint and bright areas of my image. I then exported and post-processed my image in Photoshop, playing with the exposure and contrast to best bring out the details, and more importantly, the colors of the moon.
Continue on for further analysis of my image and an explanation of these colors I keep mentioning!
Analysis
First I want to point out a few well-defined craters in my Moon Mosaic. I have chosen to highlight the Aristarchus, Copernicus, Kepler, and Tycho craters.
These craters formed when an impactor collided with the Moon in the past. These collisions are so large they cause debris to be ejected hundreds of kilometers from the impact site, forming something known as an ejecta blanket.
Let's take a closer look at the Aristarchus Crater.
Specifically, pay attention to the different colors featured in the image.
See the yellow ejecta ring surrounding the crater? This is known as the Aristarchus Plateau or Wood's Spot. This yellow coloring comes from yellow glass deposits throughout the ejecta ring.
If you focus on the center of Aristarchus you may notice some bluer regions. Mineralogy tells us that these blue regions are titanium-rich glassy deposits.
Another important colorful feature on the Moon, the Lunar Maria. Maria are large, dark basaltic plains on Earth's Moon that were formed by volcanic activity triggered by ancient asteroid impacts on the far side of the moon. Highlighted below are three specific Mare I want to touch on.
Mare Tranquillitatis, more popularly known as the Sea of Tranquillity, is predominantly blue. In this image it is partially covered by shadow and thus is a little hard to distinguish but the blue is there. The blue color comes from titanium-rich basalt.
Mare Serenitatis appears more coppery brown due to the widespread existence of brown, iron rich lavas.
Mare Imbrium's coloring is a mix of the two cases above. The bluer regions are titanium-rich basalt, the brown are iron rich lavas.
Final Remark
It's interesting to know the composition of the moon, however, it's even more interesting to actually be able to visualize it.
I learned a great deal from this project. I have used the Skynet and Afterglow softwares previously in ASTR 101L at the University of North Carolina at Chapel Hill, but never to such an extent. For reference, we were taught to take an image of the moon but it was only one little chunk/tile and only one exposure. This was my first time using a dithering pattern to create a mosaic and my first time imaging the moon as a whole.
I would like to attempt this project again in the future using data that is completely my own. However, I am proud of how my image came out and I look forward to learning more and honing my astrophotography skills!
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