Recently, design examples of wide field three mirror Mersenne-Schmidt system had been presented by R.V. Willstrop. The work presented in this paper is an extension of Willstrop's early work. By applying overall system optimization, the maximum image size within a 4-degree field of a well-designed Mersenne-Schmidt system can be as small as 0.16 arc sec. If small edge vignetting is allowed, within a five-degree wider field of view, the maximum image size of the Mersenne-Schmidt system would be as small as 0.34 arc sec. In the second part of this paper, the Mersenne-Schmidt telescope is discussed in comparison with a Schmidt camera. Discussion shows that both systems can achieve a wider field of view. However, from astronomical requirements, the Mersenne-Schmidt telescope has better image quality, wider waveband coverage, greater light power, shorter tube length and larger usage area of the primary mirror. For a light collecting area larger than that of existing ones, the Mersenne-Schmidt telescope would be a better choice for astronomical frontier work.