Simplified checking bench for telescopes and auto-checkable telescopes The field of the invention is that of the checking and measurement of the optical quality of optical instruments comprising optical elements of large dimension, of telescope type. The measurement of optical performance is the key point of the program of tests of a telescope after its assembly. More exactly this entails carrying out a set of measurements before and after a certain number of trials in vibratory or thermal environments so as to check the variations in the optical performance of the instrument when it undergoes diverse constraints. The optical quality of the instrument is characterized by a wavefront phase error, also called the "WFE", the acronym standing for "Wave-Front Error". This WFE takes into account the aberrations of the mirrors of the telescope, and also the various defects of alignment of the mirrors constituting the telescope or of the detector with respect to the telescope. Knowing the WFE, the Optical Transfer Function of the telescope, also denoted OTF, is deduced therefrom. This function is linked to the former by a conventional auto-correlation relation. Knowing the optical transfer function OTF, the Modulation Transfer Function MTFof the instrument is then calculated by switching to the modulus of the optical transfer function. The defects of alignment between the various components of the instrument not being predictable, measurement of the MTF is indispensable for characterizing the instrument. Currently, measurement of the MTF of a telescope requires the use of very precisely adjusted optical components of high optical quality, of diameter at least equal to that of the telescope and arranged in a thermally and mechanically stabilized vacuum enclosure in order to filter the vibrations. Such measurement is therefore extremely expensive, the hardware required comprising at least one optical collimator of large dimension and a stabilized vacuum enclosure together equals several million euros. This cost becomes prohibitive when dealing with checking a large telescope outside of its manufacturing unit in operational use. Indeed, it 2 becomes impossible to envisage a conventional iVITF measurement at the end customer, in the course of programs of tests with a checl