Fibre Fed Echelle Spectrograph
For Use With Telescopes of Modest Aperture

by Martin John Porter, BSc, MSc(this).

Based on a Thesis submitted to The University of Queensland
for the degree of Master of Science,
Department of Physics, 1993.
(Revised and extended 2000, 2012)


In recent years there has been a strong trend towards the automation of modest sized observatories, especially those involved with photometry. Although undoubtedly useful, there is clearly a need for more advanced instrumentation such as spectrographs. It is for such an application that this was developed.

The design of a prototype version of the instrument is presented here. Topics covered include details of the design of the spectrograph as well as component choices and an optical analysis of the complete instrument. The results of testing are then considered and areas where the design may be improved are suggested.

Although spectrographs of this type are not unique, features which distinguish this design from others are its intended use with telescopes of only modest aperture, fixed format design covering the visible spectrum in a single exposure, and short exposure times.


The document presented here is a modified form of the author’s Masters Degree Thesis, originally submitted in 1993. Modifications to the document have been for the purpose of making it suitable for electronic publication plus the inclusion of subsequent work.

It is the author’s hope that in making this document available electronically, its improved accessibility will allow it to provide "food for thought" to a much larger number of readers.


  • Introduction: Design philosophy and scope of the investigation are discussed: [open PDF].
  • Design: The design presented here is for a cross-dispersed echelle spectrograph incorporating the use of an optical fibre input and a CCD detector. [Open PDF].
  • Optical Fibre: In this part the characteristics of optical fibre chosen for this project will be discussed. [Open PDF].
  • Analysis & Collimator: In this, and the following three parts, each component of the spectrograph is analysed using a simple first order ray-trace method. [Open PDF].
  • Prism & Grating: Here the prism and grating are analysed. [Open PDF]
  • Camera/Detector & Images: Once the camera lens is investigated, the overall system can be analysed and a theoretical image of the fibre on the detector can then be calculated. [Open PDF]
  • Resolving Power & Efficiency: In this part the resolution and efficiency of the spectrograph is estimated. [Open PDF]
  • Preliminary Results: This part contains the results of preliminary testing of the spectrograph. [Open PDF]
  • Conclusions & Future Directions: [Open PDF]
  • Maths: Here are some more details of the analysis methods used. [Open PDF]
  • Bibleography: [Open PDF]
  • Updating the Spectrograph: As part of subsequent work a number of aspects of the original design were revisited. [Open PDF]