Lenses, Telescopes, Astrographs, and Mountings

  • Martin Mobberley
Part of the Patrick Moore's Practical Astronomy Series book series (PATRICKMOORE)


The f-ratio of a lens, or a telescope, is calculated by dividing the instrument’s focal length by the aperture. For the comet or nebula imager the instrument’s f-ratio (smaller means faster) is of vital importance, along with the sensitivity of the detector and the darkness and transparency of your sky. For big comets that move rapidly across the sky imaging with a very fast wide-field system has huge advantages, especially if imaging in color, whether using filtered RGB methods, LRGB methods or using a one-shot color CCD detector.


Wide Field Primary Mirror Optical Aberration Secondary Mirror Star Image 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  • Martin Mobberley
    • 1
  1. 1.Denmara Cross GreenSuffolkUnited Kingdom

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