The OMC is a quality instrument as far as optics are considered but it is also mechanically excellent. It came into being as a challenge in achieving a wide field, photo visual Maksutov Cassegrain with incredible stability and versatility.
The design is not a standard spherical one with a main mirror the same size as the corrector. That is the traditional Maksutov design but, it lacks off axis performance and suffers from coma. The OMC140 has an ellipsoidal primary which is over 12mm larger in diameter than the Maksutov corrector. This added aspherisation of the primary allows much wider flatter fields to be achieved and it virtually eliminates coma.
The carbon tube of the OMC allows almost perfect stability of focal length. The unique cantilever focusing method ensures image shift/mirror flop are things of the past. Focusing is carried out by means of a spring loaded micrometer thimble, coupled to the internal mechanism to give the most precise and the smoothest focusing action you could think of.
