Our spectrographs

All five of our observatories are equipped with Aquila spectrographs designed and constructed by Steven Lee of AAO.

In a spectrograph, the light collected by the telescope is split up the into separate colours to give a spectrum. Each spectrum tells us about the physics (dynamics) and chemistry (which elements are present) of our astronomical targets. We are collecting many spectra on several black hole systems in our Galaxy, successively with time, so we can follow how their physics and chemistry evolves. In our spectrographs, light from the object being studied is separated by wavelength by a special kind of grating called a Volume Phase Holographic (VPH) grating made by Chris Clemens' company Syzygy Optics. A normal grating has a pattern of etched lines (alternately transparent and opaque) and the light passes through and diffracts in a clear way. A VPH grating instead has a pattern in refractive index, not in transparency, so while the same diffraction process takes place essentially none of the light is lost. This means that the throughput of light through the instrument is consequently much higher. The light collected by the telescope is fed via a Fibre Injection and Guiding Unit (FIGU) made by Shelyak Instruments, from which it travels along fibres into the spectrograph enclosure. The spectrographs sit on the floor of our observatories, on cold concrete, next to the telescopes' piers.