  High precision astrometry aims at source position determination to a very
small fraction of the diffraction image size, in high SNR regime. One of the
key limitations to such goal is the optical response variation of the telescope
over a sizeable FOV, required to ensure bright reference objects to any
selected target. The issue translates into severe calibration constraints,
and/or the need for complex telescope and focal plane metrology. We propose an
innovative system approach derived from the established TMA telescope concept,
extended to achieve high filling factor of an annular field of view around the
optical axis of the telescope. The proposed design is a very compact, 1 m class
telescope compatible with modern CCD and CMOS detectors (EFL = 15 m). We
describe the concept implementation guidelines and the optical performance of
the current optical design. The diffraction limited FOV exceeds 1.25 square
degrees, and the detector occupies the best 0.25 square degree with 66 devices.
