Chromatic Moon

When bound by the limits of the human eye, the Moon can seem like nothing more than a mottled, monochromatic sphere that is too distant to understand. However, within the wavelengths of the sunlight reflected off the Moon's surface, there are hidden clues that provide insight into the composition of the Moon's surface and echos of its violent past.

Creating a color-enhanced image of the Moon has been on my bucket list for a while now, but my photography work largely ground to a halt in 2025 due to medical concerns that I am still in the process of getting a handle on. I have plenty of prepared or partially-completed projects awaiting my attention, but an impromptu shooting session on a beautifully clear night finally gave me the momentum I needed to complete this goal.

I have captured and developed countless images of the Moon over the past few decades, so I have been aware of the subtle shades of color on the Moon's surface for a while now, but the data in a single image was always unsatisfactory. After I started working on astrophotography, it was clear that image stacking would be the best process to extract these hidden details, and I now have enough experience with the process to expand into new endeavors.

Anyone who pays attention to the Moon knows that it can appear in a wide spectrum of colors depending on how the light reflected from the Moon reaches our eyes (or camera for that matter). When close to the horizon, obscured by smoke in the atmosphere, or moving through the Earth's shadow, the Moon can appear to be yellow, orange, or even a deep shade of red. When behind cloud-cover, it can appear to be shades of green, blue and purple. However, on a clear evening when the Moon is well above the horizon, it is most often observed as a monochromatic arrangement of muted greys and dark blotches accented by the bright white scars of past impacts.

The stacked, color image of the full Moon prior to color enhancement.

Click on the image to see a larger version

Our perception of an object is influenced by many factors. The wavelengths of light that an object absorbs and reflects is largely defined by the properties of the materials being viewed. However, regardless of what energy the object reflects, the human eye is only sensitive to a very small subset of the electromagnetic spectrum. To distort reality further, the composition of the rods and cones of the eye makes us overly sensitive to specific wavelengths (primarily green in humans).

So what does this mean in regard to the Moon? It means that we don’t see the Moon as it actually is; we can only interpret the Moon within the limits of our human senses. However, progressive advancements in photographic equipment and processing software now allows us to observe a larger portion of reality than ever before.

In order to extract the Moon's veiled secrets, it is necessary to take anywhere from dozens to thousands of images and stack them into a single, composite image. In the simplest terms, image stacking software analyzes the images inputted and uses that data to make statistically-driven assumptions on the most-likely value of each pixel. Over the time the images are taken, the Moon itself remains largely the same, but distortions from the atmosphere create inconsistent noise in the data that can be filtered out. The program processes millions of pixels until a final image is created with the optimized data that manifests as sharper details with less noise.

I’m still perfecting this process and the programs that make it possible, so instead of taking hundreds or thousands of images of the Moon, I only took around a hundred. I went through all of the images manually and picked 17 that were the sharpest (though I now know that I may be able to use software to do this laborious task in the future).

Color enhanced rendering of the stacked full Moon data

For many of my previous projects, I have aligned images manually because the specialized software either wasn't available to me, or the image didn't have enough reference points to align to (as has been the case with solar eclipses). However, this time the full Moon had plenty of high-contrast reference points that could be utilized by software normally used for planetary photography.

Some of the best programs for alignment and stacking are old Windows programs made decades ago by innovative astronomy/astrophotography enthusiasts. It was a bit of a challenge to get these programs to work on my M1 Macbook Pro, but I finally found a way that allows me to use the programs natively with Silicon-based Mac OS instead of needing my resource-heavy virtual desktop (Windows 11 via Parallels). I hope to create a post in the near future about installing, running, and using these programs for fellow Mac astrophotographers.

I pre-processed the 17 images using the Planetary Imaging Pre-Processor (PIPP) software to align, crop, and export the images. It was necessary to align the images because the Moon moves through the frame quickly at 1200mm. I then imported the pre-processed images into AutoStakkert to compile the 17 images into a single composite image that has more detail and less noise (see image above).

Click on the image to see a larger version

With the pre-processing complete, I pulled the resulting stacked image into Photoshop and began modifying the raw data to enhance the portions of the Moon that had more color. Unlike some astrophotography processes that assign colors to specific wavelengths of light to describe the data that the human eye cannot see (H-alpha, etc.), the slight variations of color in the Moon's reflected light exist in the visual spectrum and are determined by the specific wavelengths reflected by the materials that dominate the different regions of the Moon's surface.

I made the graphic above to help describe the Moon's features, soil composition, and some U.S. landing sites all in one image. Unfortunately, I had to darken the image of the Moon slightly so that the text is more readable. As noted in the graphic, the lunar highlands have more silicon, calcium, and aluminum which reflect the majority of the Sun’s white light. The lunar lowlands were created by massive impacts that caused lava to flow into wide basins. These basins correspond with the large dark regions that are referred to as lunar maria or the seas of the Moon. The hard volcanic rocks (basalts) in the basins that are rich in titanium tend to reflect more blue light. The largest region of blue light is observed in the Sea of Tranquility. Basalt that is richer in iron tends to reflect more red light. These iron-rich regions are most prominent in the Sea of Serenity and the Sea of Rain.

The Reflection/Absorption Paradox - Humanity has been largely inconsistent on whether objects are defined by what they are made of, or how they are observed by others. On one hand, we are told that we are what we eat, so what we absorb into ourselves determines a portion of what and who we are. The light from the Sun that our body absorbs is turned into heat that helps to keep us warm, and absorbed UV-B rays can convert molecules in our skin into pre-vitamin D3 which keeps us healthy. However, if I was asked to describe myself or others, at some point I would end up describing the physical characteristics that I can see which are defined by the wavelengths of light in the visible spectrum that the surfaces of the body reflect. At least as it applies to the electromagnetic energy of the Sun, perhaps it is correct to say that humans can be described both by the energy we absorb and the energy we reflect. In my mind, this notion may have interesting social implications when extrapolated across life and society as a whole.

Moon Image Comparison (Regular left, color enhanced right)

While the Moon may appear to have some geological similarities to the Earth, the soil on the Moon is actually very different from the layers of organic, oxidized soil that we are used to. The lack of liquid water makes the soil very dry and powdery. Millions of years of meteor bombardments have pulverized the soil and distributed it over large areas creating fine layers of lunar regolith (a thin top layer of material). Recent lunar missions conducted by India determined that this top layer of soil may be highly insulative based on temperature readings from a probe on the lander. Lunar regolith also contains a considerable amount of small glass beads formed by the incredible heat of meteor impacts.

Beyond its compositional differences, the individual particles of lunar soil differ greatly from terrestrial soil. The lack of erosion from wind, water, and tectonic forces means that the fine particles of soil are jagged and can be dangerous to soft membranes such as those in human lungs and nasal passages. The Moon is also missing a functional magnetosphere and sufficient atmosphere to repel charged particles from the Sun (and from the tail-end of the Earth’s magnetosphere that also sheds charged solar particles towards the Moon), so the soil has a notable electric charge that causes it to bind aggressively to surfaces. In short, while the Moon may consist of similar elements to that of Earth, there are many ways in which the lunar environment is much more inhospitable and perilous. As difficult as it can be for humans to survive on Earth at times, those struggles pale in comparison to how hostile other moons and planets in our solar system can be.

This is only the first of what will hopefully be many more studies into stacking lunar images. I want to try to increase focal length and combine more images for more detail, compare video vs photo stacking, and experiment with different Moon phases that create more contrast in the lunar surface. Only time will tell if I can fulfill those aspirations, so follow me on my socials for updates (links at the bottom right of the page), or sign up for email notifications of new posts (sign up at the bottom, left of the page; I don't send any emails other than notifications of new blog posts).

© 2017-2026 Shaun C Tarpley

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