Bring the Moon's Real-Time Appearance to Your Desk

Have you ever wondered what the Moon looks like at this very moment, even if it's hidden behind clouds or below the horizon? A clever project by Karsten Mueller brings that experience to your desk. Using a round display, an ESP32-S3 microcontroller, and a 3D-printed case, this device shows an accurate approximation of the Moon's appearance based on your local time, latitude, and longitude. Unlike standard moon phase displays, it adjusts for your precise location and accounts for times when the Moon is not directly visible. The software makes it possible to see a representation of the Moon even during daylight or when it's obscured by Earth. The project is fully open-source, with imagery options ranging from a personal photo to NASA data. Here's a closer look at this fascinating gadget.

What exactly is this desk Moon project?
How does the device calculate the Moon's appearance?
What hardware components are used?
Can it show the Moon even when it's not visible?
Where does the imagery come from?
Is this project open-source and where can I find it?
What makes this different from a typical moon phase display?

What exactly is this desk Moon project?

This project, created by maker Karsten Mueller, is a small desktop device that displays a realistic image of the Moon as it would appear from your exact location at any given moment. It consists of a circular display housed in a simple 3D-printed case, all controlled by an ESP32-S3 microcontroller. The key innovation is the software: instead of just showing a generic moon phase, it takes into account your local time, latitude, and longitude to render an approximation of the Moon's current appearance. This means the terminator line—the boundary between day and night on the Moon—matches what you would see if you looked up, regardless of whether the Moon is actually visible in the sky.

Bring the Moon's Real-Time Appearance to Your Desk — Source: hackaday.com

How does the device calculate the Moon's appearance?

The calculation relies on astronomical algorithms that simulate the Moon's orbit and the angle of sunlight hitting it. By entering your local time, latitude, and longitude, the ESP32-S3 computes the exact phase and orientation of the Moon as seen from your location. It then generates a corresponding 2D image, mapping the lit and shadowed areas. The result is a dynamic display that updates as the Moon progresses through its cycle. Even if you are in a different hemisphere, the device adjusts the orientation so the terminator aligns correctly with your perspective. This level of detail is far beyond simple phase icons, making the device both a functional tool and an educational piece.

What hardware components are used?

The device is built around three main components:

Circular display: A round LCD screen that shows the Moon image at a resolution suitable for a desktop gadget.
ESP32-S3: This powerful microcontroller handles all computations, including timekeeping, location-based calculations, and driving the display.
3D-printed case: A simple enclosure that holds the electronics together and gives the device a clean, compact look.

The simplicity of the hardware makes it easy to replicate. You can source the parts from common electronics suppliers and print the case yourself. The project's GitHub repository includes the necessary 3D files, firmware, and instructions.

Can it show the Moon even when it's not visible?

Yes, that's one of its most impressive features. The software calculates the Moon's appearance regardless of whether it is actually above the horizon, hidden by Earth (during a new moon or eclipse), or obscured by daylight. For instance, during the day, the Moon may be present in the sky but washed out by sunlight—the device still shows its correct phase. Similarly, when the Moon is on the opposite side of Earth, it displays the dark side (new moon) or whatever portion is illuminated from your perspective. This continuous representation helps you understand the Moon's position and phase even when you can't see it.

Where does the imagery come from?

Karsten Mueller initially used a photograph he personally took of the Moon as the base image for the display. However, the software also includes an option to pull imagery from NASA's database. This allows you to choose between a custom, high-resolution photo or a standardized NASA image. The device then applies shading and rotation to this base image according to the calculated phase and orientation. The result is a realistic view that mimics the texture and features of the lunar surface. Having both options gives flexibility: the personal photo adds a unique touch, while NASA data ensures accuracy and consistency.

Is this project open-source and where can I find it?

Yes, the project is fully open-source. The original write-up is in German, but Karsten has also provided an English page on Hackaday.io. All source code, 3D printing files, and assembly instructions are available on GitHub. You can visit the Hackaday.io project page for details and then head to the linked GitHub repository to download everything needed to build your own. The open-source nature means you can modify the software or hardware to suit your preferences, making it a great weekend electronics project.

What makes this different from a typical moon phase display?

Standard moon phase displays—such as those on clocks or weather stations—show a simplified, generic representation of the Moon's phases (e.g., crescent, half, full) that cycles roughly every 29.5 days. They do not account for your geographic location or the Moon's orientation in the sky. This project goes far beyond that by calculating the precise terminator line and rotation as seen from your local time, latitude, and longitude. It also works when the Moon is not visible, which a typical display cannot simulate. Moreover, it uses a realistic image rather than a symbol, and it updates continuously. The result is an accurate, educational, and visually appealing device that fosters a deeper connection with the Moon.

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