Spectroscopy, from initiation to performance
22 132,80 € incl. VAT - 18 444,00 € excl. VAT
The eShel III spectrograph is a professional-grade, multi-wavelength fibre-optic instrument.
When it is not possible to choose between resolution and spectral range, as is the case, for example, in the study of exoplanets, an Echelle spectroscope is required, as it provides numerous high-resolution orders (R = 10,000).
The eShel spectroscope covers a range of approximately 370 to 910 nm (orders 25 to 60).
The complete eShel system comprises the spectroscope itself, as well as the guide cap (F/6), the calibration module (with ThAr lamp), the high-voltage power supply and the optical fibres (20 m long).
| Description | Shelyak ref. | Included |
Acc. type
|
Cooled
|
Comment
|
| Camera Atik 460EX Mono | SE0124 | Camera Science | yes | The standard CCD camera for the eShel II | |
| Caméra ASI2600MM-Pro | EL0271 | Camera Science | yes | New generation CMOS camera |
The eShel III spectroscope enables work across a wide spectral range (390 to 700 nm) at high resolution (R = 10,000). This is made possible by the use of multiple orders (in this case, between 25 and 60); an Echelle spectrum can be read ‘like a book’: the end of one order is found at the start of the next.
The decision was taken to offer a fibre-optic solution in order to improve the accuracy of radial velocity measurements (the instrument is separate from the telescope, ideally in a temperature-controlled room) and to enhance user comfort.
We have developed this instrument based on our experience with the Musicos and Narval professional spectroscopes.
This technique achieves high spectral resolution by using the >30 diffraction orders of a grating The resulting spectrum passes through a cross disperser, which “slices” the spectrum into successive orders, occupying the entire surface of the camera’s sensor. In this way, the entire spectral range in the visible spectrum is obtained over some twenty orders (in the case of the eShel).
Schematic diagram of an Echelle spectrograph (© François Cochard)
This is the main module that generates the Echelle spectrum. It covers the spectral range from approximately 370 to 910 nm with a resolution of R=10,000 (using an ASI 2600 MM Pro camera, not included). It has an FC/PC connector for attaching 50 µm object fiber. 
Example using the solar spectrum
Sunlight spectrum
Orders #22 through #61 are uniformly focused.
Spectrum of Chi Oph Be star
This allows us to process orders #25 through #60 and extend the usable spectral range from approximately 370 to 910 nm. 
The manual version of this lens comes with a helical focuser, enabling precise focusing of the spectrum. There is also a motorised version fitted with a PrimaLuce Lab motorised focuser (ideal for remote operation or when the spectrograph is not located next to the control PC).
By Olivier Garde The eShel II spectroscope features an 85-mm focal-length camera lens that is no longer manufactured; an alternative had to be found, so Shelyak Instruments designed its own 122-mm focal-length Petzval-type lens. This “custom” design has made it...
You'll find all our Demetra video tutorials on this web page. Demetra is a free software package for processing spectra from the ALPY 600, LISA and eShel spectrographs from the Shelyak Instruments range. Playlist of Demetra tutorials Tutorial #1 Introduction to...
