Cosmic Sleuth: Build a DIY Spectrometer to Decode the Secrets of Starlight!

Gazing at the stars, have you ever wondered how we know what they are made of? The answer lies not in a spaceship, but in the light itself. Every star, nebula, and galaxy broadcasts its cosmic signature across the universe encoded in a rainbow. With this DIY Smartphone Spectrometer, you can build the very same tool astronomers use to capture these signals and become a cosmic detective in your own home.

This project guides you in crafting a precision spectrometer from 3D-printed parts and a diffraction grating. It transforms your smartphone into a powerful scientific instrument, allowing you to perform the same foundational analysis as the Hubble or James Webb Space Telescope: spectroscopy. Uncover the hidden elements in light bulbs, recreate the Sun's absorption lines, and understand the physics that empowers us to explore the cosmos from billions of light-years away.

Let's build a bridge between your workshop and the stars!

A Maker's Journey to the Stars

This project is a journey into the heart of astronomical discovery. I built it to make the abstract, tangible. To take a principle confined to textbooks and massive observatories and place it squarely in the hands of a curious maker.

You will gain hands-on experience in the core skills that power modern astrophysics:

1. Precision Optical Engineering: Assemble a stable light path, understanding how a slit, lens, and diffraction grating work in concert to resolve light's components.
2. The Art of Calibration: Just like astronomers calibrate their massive instruments, you will use known light sources to transform colorful smartphone images into precise, quantitative data—a pixel-to-wavelength map.
3. Data Detective Work: You will learn to read spectral lines like a secret code, using reference tables to identify elements, mirroring how scientists analyze stellar data.
4. Connecting Earth and Sky: By analyzing the Sun's spectrum from your backyard, you will perform the same analysis as an astronomer studying a star a hundred light-years away.

This is your launchpad into a deeper understanding of the universe. It proves that the tools for cosmic exploration can be born from creativity, curiosity, and a 3D printer.

Supplies: Gathering Your Starlight Capture Kit

Hardware Components

1. Black 3D Printed Parts (Main Body, Slit Assembly) -to create a light-tight "observatory" for your sensor -STL files provided below.
2. Diffraction Grating (500-1000 lines/mm) - The heart of the device, your "light-splitter."
3. Smartphone with a capable camera.
4. Small Screws (M2/M3) for a solid build.
5. Universal Smartphone Telescope Mount

https://e.tb.cn/h.S6nlyYemhOpCZng?tk=8K0IfZQe3Xd

Cosmic Data Resources

1. Your Smartphone Camera App (with manual focus capability).

https://publiclab.github.io/spectral-workbench.js/examples/new-capture/

1. Spectral Line Reference Table (Your "Decoder Ring" for elements, provided in the Appendix).

Your spectrometer is a miniature observatory. Its design is optimized for stability and precision, ensuring the light from a source like a distant star—or a nearby lamp—is analyzed without distortion.

Printing Your Cosmic Tool:

1. Download the STL files attached to this step.
2. Print with Purpose:
3. Material: Standard PLA is perfect.
4. Infill: 25% provides a great balance of strength and speed.
5. Resolution: 0.2mm layer height for a smooth finish.
6. Post-Processing: Ensure the two body halves fit together snugly. A light-tight seal is crucial, just like in a real space telescope!

You are now assembling the core of your spectrometer: the optical tube. This single, 3D-printed component is meticulously designed to house the critical optics and create a precise path for light—its integrity is key to capturing clear, accurate data.

1. The Monobloc Optical Tube: A Sealed Light Path

Your spectrometer's body is a monobloc optical tube, 3D-printed as a single, continuous unit from black material. This design is crucial for two main reasons:

1. Inherently Light-Tight: The black material absorbs stray light, and the seamless construction prevents light leaks. This ensures that the only light reaching your camera is the one that has passed through the intended optical path, just like in space telescopes that must block out all unwanted light to observe faint celestial objects.
2. Precision & Stability: The fixed geometry guarantees that the internal components, once installed, remain perfectly aligned. This rigidity is essential for obtaining consistent, reproducible results.

2. The Pre-Printed Entrance Slit: Defining the Signal

At the front of the tube, you'll find the pre-printed entrance slit.

1. Its Role: This slit is your spectrometer's aperture. Its narrow, fixed width is VITAL because it defines a thin, precise line of the light source. This is the first and most critical step in creating a high-resolution spectrum. A wider slit would allow too much light to enter from different angles, resulting in a blurred and poorly resolved spectrum, making it difficult to distinguish individual emission or absorption lines.

3. Install the Diffraction Grating: The Heart of the System

This component performs the core magic of splitting light into its constituent colors, a process identical to that used in the most advanced astronomical spectrographs.

1. Action: Carefully secure the diffraction grating film over its designated rectangular port inside the pre-printed tube. Ensure it is seated flat and securely.

4. Align with Your Smartphone: Completing the System

Objective: To couple the spectrometer's optical tube perfectly with your smartphone's camera, ensuring the entire spectrum is captured sharply.

Operation:

1. Attach the provided phone mount to the end of the optical tube.
2. Secure your smartphone in the mount, carefully aligning the tube's exit port with the phone's main camera lens. Ensure there is no gap between the tube and the phone's camera glass.
3. The final configuration should have the spectrometer's pre-printed entrance slit pointing directly towards your light source, and the camera looking straight into the tube, ready to capture the dispersed spectrum.

Objective: To capture the spectral image of a light source and extract characteristic wavelength data for analysis.

Procedure:

1. Capture the Spectrum:
2. Launch the web application and enter the capture mode.
3. Point the spectrometer's slit directly at your target light source (e.g., a light bulb, flame, or reflected sunlight).
4. Ensure the light intensity is moderate—neither too bright to cause overexposure nor too dim to be detected—to prevent spectral distortion.
5. On the spectral analysis web interface, click the "Capture" button to acquire the spectrum image.
6. Extract Characteristic Data:
7. Open the saved spectral image for analysis.
8. Using the image's calibrated scale or the software's analysis tools, precisely measure and record the wavelengths (or frequencies) of the observed dark lines (absorption spectra) or bright lines (emission spectra).
9. Accurately note the pixel positions corresponding to these characteristic spectral features, as this data is essential for identifying chemical elements.

Your spectrometer is now a functional instrument, ready for its "first light" observations. Conduct these experiments to master its operation and discover how the light from everyday sources connects to the grand phenomena of the cosmos.

Mission 1: Decode Artificial Stars

1. Primary Objective: To understand the fundamental difference between continuous, broad-spectrum sources and discrete, atomic emission sources. This is the first step in classifying any light source, whether in your home or in a telescope's eyepiece.
2. Procedure: Capture and compare the spectra of an LED bulb and a Compact Fluorescent (CFL) bulb.
3. The Cosmic Link: The LED's smooth, broad peaks are characteristic of semiconductor physics, while the CFL's sharp, discrete lines are the unmistakable signature of atomic transitions in mercury vapor. Analyzing these differences trains you to distinguish between different physical processes that generate light, a foundational skill for interpreting the complex mix of signals from distant stars and galaxies.

Mission 2: Analyze Our Home Star, the Sun

1. Primary Objective: To observe and identify absorption lines in a continuous spectrum, directly replicating the method used to determine the chemical composition of stars.
2. Procedure: Safely point your spectrometer at the blue sky (indirect sunlight, NEVER at the Sun directly) to capture the solar spectrum.
3. The Cosmic Link: You will see the Sun's continuous rainbow crossed by dark Fraunhofer lines. These are the unique absorption fingerprints of elements like hydrogen and calcium in the Sun's cooler outer atmosphere. Identifying the prominent hydrogen-alpha line at 656.3nm means you are detecting the primary fuel of our Sun—and the most abundant element in the universe.

Mission 3: Recreate the Glow of a Stellar Nursery

1. Primary Objective: To observe pure, bright emission lines and understand their origin in low-density, excited gases—the same state as many glowing cosmic clouds.
2. Procedure: Capture the spectrum of a neon sign or a hydrogen gas discharge tube (if available).
3. The Cosmic Link: The bright, isolated lines you see are the hallmark of emission nebulae, like the Orion Nebula—vast clouds where new stars are born. In these cosmic nurseries, ultraviolet radiation from hot young stars excites the surrounding gas, causing it to glow with specific colors, just like your terrestrial light sources.

Take your discoveries further. Compare the solar spectrum you captured to published data from observatories. Can you find the lines for Calcium (at 393.4, 396.8nm) or Sodium (the D-line)?

Try to measure the spectrum of a remote LED bulb. Does its composition change with color?

Congratulations, Cosmic Sleuth! You have not just built a device; you have acquired a new sense. You can now see the hidden components of light, a skill that forever changes how you perceive the world and the universe.

This project embodies the spirit of space discovery by directly connecting a hands-on maker project to the most profound techniques of space exploration. The light from a star is a message. With curiosity and this tool, you have learned to read it.

This is only the beginning. Where will your curiosity take you next?

1. Upgrade to a Raspberry Pi HQ Camera for deep-space-level sensitivity.
2. Write a Python script to automate your analysis.
3. Point your spectrometer at the Moon and compare its reflected spectrum to the Sun's direct light.

The cosmos is calling. We are all made of stars. Now you have the tool to see it.

Let's build a gallery of light from our community of cosmic makers!