Novel mirror telescope for prominences

The present investigation is concerned with the theoretical principles and the practical realization of a mirror telescope for the observation of prominences, taking into account an instrument with a 4-A filter and a conical diaphragm. In connection with the design of the instrument, a perfect solution could be found for problems related to scattered light. A short design length could be achieved, and there is little generation of heat during operation. No chromatic correction is required, and it is possible to reduce the aperture ratio of a reflector to 1/10. Attention is given to the factors responsible for the occurrence of scattered light, the employment of parabolic mirrors without coating, parabolic mirrors with coatings obtained by means of a vapor deposition process, the use of a titanium dioxide coating, details of practical design, and the first results obtained with the new instrument.