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Simple CCD Spectrographs

(c)1997..2016 John E. Hoot
SSC Observatories

Traditional spectrograph designs are too large and complex to be useful on small amateur telescopes. Rather than using the traditional format, the slitless spectrograph discards all of the optics to the left of the diffraction grating in the figure below.

The Slitless Imaging spectrograph are characterized by several key attributes that contribute to their relative simplicity:

  • Small Dispersion Angles
  • On Axis Imaging
  • Relatively Course Diffraction Gratings

These features allow for the simplification of the mathematics of classical spectrographs as follows:

An example of simple CCD spectrograph is diagramed below:

 Software to generate 100 LPI and 200 LPI grating on conventional overhead transparency films along with software to extract and process spectra can be found on SSC's web page.

CCD spectra are taken and processed in the same manner as any other CCD image. You want to be sure that the image does not saturate and that both the source star and spectra are contained in the frame. Best results are obtained when spectra or oriented parallel to the long axis of the CCD imaging chip.

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