Designing for high reliability and low maintenance should not be left to just the mechanical aspects of an optical system. Ideally, the optical design itself should strive towards these goals. As an example, we consider an infrared telescope which is intended to cover a moderate field-of-view at fast f# speed. There are a variety of two-element designs that might be considered as design candidates and which will perform well, on paper. The actual performance of a system often depends, however, on how well it can be aligned and how stable the alignment is under adverse environmental conditions. This paper describes a single element design which completely avoids this problem, for there is nothing to misalign. It is a thin aspheric Mangin mirror which has several desirable features in addition to good performance. In some cases the aspheric can be omitted. Representative design examples are shown and discussed.