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Observational Techniques 1: Optical and Infrared Astronomy

Observational Techniques 1: Optical and Infrared Astronomy

Course Outline: 

The aim of this course, which comprises nominally of 20 lectures plus associated hands-on exercises/ projects, is to give a general introduction to optical and infrared observational astronomy, emphasising the instrumentation and techniques used. This includes discussion of basic telescope optics and design, active and adaptive optics, techniques for light detection and the principles and practices employed in photometry and spectroscopy.

Illustrated examples are given of the different types of science achieved by various astronomical instruments and techniques. Practicalities of observing and reducing astronomical data are also introduced in the course. The concept of the Virtual Observatory (VO) is presented, which includes a tutorial session in the NASSP computer laboratory using various VO tools. Particular emphasis is given to get practical experience on data reduction and analysis through various tutorial sessions.

Course Assessment

A written examination at the end of the semester will make up 50% of the course assessment and remaining 50% comprise based on photometric (15%) and spectroscopic (15%) data reduction exercises. A short project based on the Virtual Observatory exercises will comprise 20% of the assessment.


The lectures will cover the following major topic areas:
  • Observing Basics (1 x 2h lectures)

 Astronomical coordinate systems; spherical trigonometry; precession & nutation; parallax; proper motions; stellar aberration; atmospheric diffraction and dispersion; time systems.

  • Telescopes (2 x 2h lectures)

Basic optics; aberration theory; telescope parameters and configurations; telescope lenses, mirrors, tubes, mounts, domes and enclosures; mirror coatings; active and adaptive optics (A-O); optical nature of the Earth’s atmosphere, Fried parameter and structure parameters; Optical and Modulation Transfer Functions; Strehl ratio; science with AO; modern large telescopes

  • SALT (1 x 1h lectures)
The Southern African Large Telescope (SALT).
  • Detectors (2 x 1.5h lectures)

The human eye; the magnitude scale; photographic techniques; photoelectric effect; photomultiplier tubes; image tubes; microchannel plates; semi-conductor basics; CCD principles; CCD design and operation; noise sources and signal to noise equation; cosmetic defects; practicalities of CCD data reductions; demonstration of CCD operation.

  • Photometry (1 x 2h lectures)

Absolute and bolometric magnitudes; colour index; blackbodies; filters and photometric systems; spectral energy distributions; two-colour diagrams; dust extinction and reddening; line blanketing; colour-magnitude (C-M) diagrams; atmospheric extinction, absorption and emission; reducing photometric data; differential photometry; Fourier theory and period analysis. 

  • Spectroscopy Principles (1 x 2h lectures)
Early history; dispersion and prisms; objective prism spectroscopy; diffraction gratings, the grating equation and grating parameters; échelle gratings; grisms; volume phase holographic gratings (VPHGs); spectrometer design, collimators and cameras; spectrograph examples including the SALT RSS; slit effects; CCD gain and digitization; signal to noise calculations; sky background. 
  • Virtual Observatory (1 x 1h lectures)

Definition of the VO; VO tools; VO examples.

  • Near Infrared Techniques (1x 2h lectures)

Challenges posed by observing at infrared wavelengths and how they are dealt with; infrared detectors and photometers and their use on the various telescopes at Sutherland. A detailed discussion of why we bother with observing at infrared wavelengths, given how difficult it is..

  • Astronomical Data Reductions (Photometric and Spectroscopic) and Virtual Observatory

Different types of observations, reduction methods and resources available; CCD data reductions and the tools; FITS data format; errors and signal-to-noise (S/N)

  • A. Photometric Data Reductions (2 x 2h lab)
photometric reduction methods and calibrations; astrometry and source detection; the IRAF data reduction package. Practical exercises in reducing real data.
  • B. Spectroscopic Data reductions (2 x 2h lab)

spectroscopic reduction overview; data reduction methods; Wavelength and flux calibrations; the IRAF data reduction package. Practical exercises in reducing real data. 

  • C. Virtual Observatory Lab (2 x 1.5h lab)
Lecture Resources 
Lecture notes and PDF copies of the lecture presentations are available on the NASSP website for most of the OT1 lectures. See http://www.star.ac.za/david-buckley
Most of this material pertains to the 2010 course, but is still mostly relevant. Updates will be provided 
during the semester.

Programmes | by Dr. Radut