Astronomical spectroscopy for research, industry, education and leisure

Description – eShel

is your complete echelle spectroscopy solution for your astronomical projects. It is based on our strong experience in spectroscopy (with design and manufacturing of the Lhires III and Lhires Lite) and nights of observations including with MuSiCoS & Narval spectroscopes. This practical experience helped us to design a robust and productive solution in the field.

We designed the spectroscope with Christian Buil, a higly recognized optician expert. The software module has been written by Michel Pujol, an expert in Tcl/Tk and AudeLA platform. They both complement our expertise to bring you the best solution in echelle spectroscopy for astronomy!

Choice of optical fibre has been made to increase radial velocities measurement accuracy and for a better confort in using the eShel.

The complete solution is made of four major modules:

Fiber Injection & Guiding Unit

  • M42 T-adapter telescope interface
  • Backfocus 43mm
  • Miror with light going through a 50µm hole for the f/6 standard version (a 75µm f/9 version exists – contact us for details)
  • Calibration fiber input (remote controlled mirror position)
  • Fibre optics
    → 50µm object fiber
    → 200µm calibration fiber
    → fibers protected by metal/plastic casing
    → FC fiber connectors
  • Guiding camera (C-mount)

some guiding images on Saturn, star and Thorium lamp

autoguiding on a star

Calibration Unit

  • Thorium-Argon lamp with high voltage power supply for precise calibration
  • Flat lamp for echelle order geometry and blaze processing
  • Electronic to control remotely calibration frame acquisition


echelle spectroscope

  • Cross-dispersed echelle spectroscope
    → f=125mm collimator (f/5)
    → R2 high efficiency echelle grating
    → coated prism cross-disperser
    → 85mm f/1.8 objective
  • Compact
  • High power of resolution R=10000
  • Visible domain (around 450-700nm)
  • Optimized for large telescope (50µm fiber)


eShel Software

  • Easy to use
  • Open source, based on AudeLA platform and Tcl/Tk language
  • work on MS Windows platform
  • multi-language support
  • Remote-controlled operations
  • Automatic spectra reduction procedure after acquisition
  • FITS file support with multiple HDU
  • Export individual orders or merged spectrum
  • Download here an exemple of a processed echelle spectrum of our Sun (open with multi-HDU FITS reader such as fitsview).


exemple of a calibrated spectrum of beta Per, between H-beta & H-alpha

Spectrum of delta Scorpii (Be star). Note the evident emission of Balmer lines. Canon 40D, 9 x 300 s exposure with the 0,2m telescope (C.Buil)


  • Several applications are possible with the echelle spectroscopy solution:
  • Be stars monitoring
  • spectroscopic binaries
  • exoplanets
  • planetary nebulae
  • spectral classification
  • asteroid classification
  • lunar geology
  • planet composition
  • abundance measurement
  • novae
  • RR Lyrae
  • Herbig Ae/Be
  • T Tauri
  • Wolf-Rayet

beta Lyr – Shelyak [:-)] & P Cygni – 7 x 300 s exposure / 0.2 m tel. Click to enlarge

Here is also a good exemple of echelle spectroscopy with an animation of raw images of BW Vul, a pulsating star. 5min expoures, 60cm f/3.5 telescope at pic du Midi; QSI 516s camera (click on animation image to enlarge):

Here is a spectrogram of BW Vul around Sodium doublet:

External links

Software & Documentation

Get our user documentation here:

Check latest beta version of AudeLA software which now inlcudes eShel module in standard:

Check also vcredist_x86 Microsoft program that you may need to install fo AudeLA to run properly.

For a personal quote, send an email to: