AST 201: Introduction to Astronomy

3 credits | Prerequisites: PHY 101, MAT 104

Course rationale

This is an elective course designed for students majoring in physics, mathematics, engineering or computer science. Students can take it as part of a minor or specialization in astronomy and astrophysics or as a free elective. The course intends to give an overview of observational astronomy including basics of light, optics and telescopes, coordinate systems and detection and data analysis mechanisms.

Course content

History: a brief overview of ancient and medieval astronomy; revolution of Copernicus, Galileo, Kepler and Newton; rise of modern multi-wavelength astronomy. Light: nature of light, messengers in astronomy; wave, particle and ray models of light; measurement of light: luminosity, flux, brightness; spectra, astronomical magnitude systems. Uncertainty: accuracy and precision, populations and samples, population statistics, probability distributions, estimating uncertainty, central limit theorem, propagation of uncertainty. Spacetime and motion: astronomical coordinate systems, ICRS, the line-of-sight dimension, distance measures, atomic time, solar time, space motion, proper motion, radial velocity. Catalogs and databases: star names, star catalogs, names and catalogs of non-stellar objects outside our solar system, atlases and charts, websites and databases. Optics for astronomy: principles of geometric optics, reflection and refraction, lenses and mirrors, optical fibers, optical materials, simple telescopes, telescopic resolution, seeing, aberration, shapes of spherical surfaces, coma, astigmatism. Telescopes: telescope mounts and drives, reflecting telescope optics, space telescopes, ground based telescopes, large mirrors, computers, observatory engineering, adaptive optics. Matter and light: atomic energy levels, absorption and emission, collision and excitation, isolated molecules, solid-state crystals, photoconductors, MOS capacitor, the vacuum photoelectric effect, superconductivity. Detectors: detection mode, efficiency and yield, noise, linearity, stability, response time, CCD, photo-emissive devices, infrared arrays, thermal detectors. Digital images: detector arrays, pixels and response, digital images, CCD gain, digital image manipulation; preprocessing array data: bias, linearity, dark, flat and fringe; combining and mosaicing images, digital aperture photometry. Photometry: a short history of photometry, the response function, color indices, photometric systems, passage of light from source to detector, data reduction strategy, atmospheric effects, extinction. Spectrometry: dispersive spectrometry, dispersing optical elements, spectrometers without slits, split and fiber spectrometers, spectrometer design for astronomy, spectrometric data handling, interpreting a spectrum.

Course objectives

  1. Introduce the nature of light and its enormous role in astronomy as the messenger.
  2. Evaluating the uncertainties inherent in the measurement of light.
  3. Situate all astronomical objects in spatio-temporal coordinate frames.
  4. Introduce the basic principles of optics for astronomical telescopes.
  5. Describe the working principles of detectors as the interface between light and matter.
  6. Explain the conversion of detected information into digital images.
  7. Introduce the methods of measuring light (photometry) and its spectra (spectrometry).


  1. Frederick R. Chromey, To Measure the Sky: An Introduction to Observational Astronomy, Cambridge University Press, 2010.
  2. Hale Bradt, Astronomy Methods: A Physical Approach to Astronomical Observations, Cambridge University Press, 2004.
  3. Fundamental Astronomy, edited by H. karttunen et al., 6th edition, Springer, 2017.
  4. M. Shane Burns, A Practical Guide to Observational Astronomy, CRC Press, 2022.