The Couder telescope - better than the Schmidt?

The present investigation is concerned with an application of slight modifications to the original Couder design. These modifications make it possible to obtain images under 0.4 arcsec in diameter up to 1.8 deg off axis in an f/2.5 telescope, and under 1 arcsec 2.25 deg off axis at f/2. It is pointed out that because of its perfect achromatism, the Couder telescope becomes fully competitive, in terms of image quality, with the Schmidt camera. Attention is given to the original Couder design, the modified Couder telescope, and a comparison of the modified Couder telescope with the Schmidt camera.