The Atmosphere Between Us and the Stars.

Using the Night Sky to Probe the Atmosphere Above Us

Introduction

Ground-based astronomers do not observe stars directly. They observe starlight after it has passed through the Earth’s atmosphere. Molecules, aerosols, clouds, and airborne particles scatter or absorb some of this light before it reaches the telescope. For astronomers, this atmospheric extinction is a source of uncertainty that must be understood and, where possible, corrected. For atmospheric scientists, however, the attenuation of starlight contains information about the atmosphere itself.

Recent hazy conditions in Singapore have made conventional astronomical observations difficult. In this project, you will turn that difficulty into the subject of your investigation.

Project Details

Your group has joined an astronomical research laboratory. The recent period of haze has opened up the possibility of investigating questions that we might not ordinarily explore.

Specifically, your PI wants to know whether observations of the night sky can help us investigate the atmosphere. In particular, she wants to know:

What can observations of the night sky tell us about the optical properties of the atmosphere at our observing site, and how reliable are those conclusions?

The laboratory has a telescope, a digital camera, a spectrometer, and computational tools. Your group should decide which of these resources to use, then develop and test a method for assessing the optical properties of the atmosphere during your observing period.

Your group will need to decide:

  • which astronomical objects to observe and why they are suitable for your investigation;
  • which primary measurable quantity to use and what atmospheric property it represents;
  • how to collect, calibrate, and analyse your observations;
  • which atmospheric, instrumental, and computational effects could influence your measurements;
  • how to test the repeatability of your method and assess its uncertainty; and
  • what conclusions your evidence can reasonably support.

Possible indicators include the attenuation of starlight, sky brightness, signal-to-noise ratio, image contrast, the number of detectable stars, or another quantity you can justify. These indicators are not interchangeable, and you do not need to measure them all.

Explain whether your chosen quantity is a direct measurement, a value derived using a model, or a proxy for atmospheric conditions.

A useful outcome may be a working measurement, a qualified estimate, or a clear account of why the method needs further refinement. In each case, explain your reasoning, uncertainties, limitations, and what you would improve next.

Here are some publications to get you started. The objective is not to reproduce a published method mechanically or to guarantee a definitive haze measurement. Use the literature to inform your choices, then design, test, and refine a method suited to the available equipment, observing conditions, and project duration.

  1. Jurado Vargas, M., et al. (2000). Atmospheric extinction of stellar radiation in the optical domain. European Journal of Physics, 21(3), 245–252. https://doi.org/10.1088/0143-0807/21/3/307

  2. Lanciano, O., & Fiocco, G. (2007). Nighttime measurements of atmospheric optical thickness by star photometry with a digital camera. Applied Optics, 46(22), 5176–5182. https://doi.org/10.1364/AO.46.005176

  3. Román, R., et al. (2025). Star photometry with all-sky cameras to retrieve aerosol optical depth at nighttime. Atmospheric Measurement Techniques, 18, 2847–2875. https://doi.org/10.5194/amt-18-2847-2025

  4. Malasan, H. L., et al. (2020). Study of aerosol content based on spectrophotometric observations: A comparison with long-term extinction profile from photometric observations. IOP Conference Series: Earth and Environmental Science, 537(1), Article 012008. https://doi.org/10.1088/1755-1315/537/1/012008

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