The Two-Mirror Telescope (2MT)

Abstract

SUMMARYTwo eight-metre mirrors on an alt-azimuth mount are considered as a Future Large Telescope. The combined collecting area is ten times that of a four-metre class telescope, and the main modes of use are for optical spectroscopy and infrared imaging. In one square arc second, at 10µm wavelength, the telescope with adaptive auxiliary optics will yield 30 to 100 fully resolved image elements (not speckles). The mechanical arrangement proposed to give path length stability is to link the two tube centre sections along a horizontal axis and to use a total of four altitude bearings. A combined focus is necessary for the highest angular resolution, but other work such as spectroscopy can be carried out either at a combined focus or using separate instrumentation for the two eight-metre apertures. Twin prime and Cassegrain foci and horizontal Nasmyth platforms are intended for such pairs of spectrographs and other instruments, depending on their weight and field requirements. A pair of prime focus spectrographs with f/0.8 cameras is one appropriate system. (The horizontal Nasmyth platforms to accommodate larger spectrographs are a feature of this telescope which is not feasible in other MMT-type configurations). Another significant capability is that for a coud6-type light path from either aperture to the vertical axis. This can be achieved with four reflections (including the primary) for some applications. In addition to the conventional uses of the coudg light path, there is the possibility of using it to produce interferometric links to other telescopes. These links may be important as a future extension of the instrument.