El TIGRE (previously known as HRT) is a private, thus flexible, telescope initally used at Hamburg University (hence its name). It is installed in La Luz, in Mexico, a 2400 meter site belonging to the University of Guanajuato. The involvement of the University of Liège has been on the logistics side: telescope accommodation and infrastructure, as well as part of the Hamburg to Mexico transportation costs.
The telescope's primary mirror is of 1.2 m diameter, i.e. well adapted for bright stars studies: it is of Nasmyth type with a modern Alt-Az mount (like the ESO/VLT in Chile). This telescope, at the forefront of technology, collects the stellar light via a 3-mirror system and concentrates it on a platform on the side of telescope, where the main instrument is located. The latter thus remains fixed while the telescope is moving, ensuring a high stability.
The telescope is equipped with an instrument called 'spectrometer' that accurately analyzes the spectrum, i.e., the distribution of light with respect to frequency. Each chemical element holds a unique spectral signature and each physical phenomenon leaves a "foot print" in the spectra. The spectrum is thus a kind of celestial bar-code that contains the full information to understand the stars. The only challenge is to record these spectra correctly. To this aim, the TIGRE instrument is of échelle-type hence it possesses a very high spectral resolution: it can thus distinguish all the details of the luminous messages sent by the stars. Such a high resolution is required in order to accurately determine the stellar properties.
The specificity of the project is to enable long sequences of observations (months to years), which is no longer possible in large observatories where only a few hours of observing time are allocated. Therefore el TIGRE is a unique tool for stellar astrophysicists.