Astronomical infrared telescopes

Consideration is given to the requirements on the image quality and potential gain in observing efficiency with large infrared telescopes. It is concluded that such large instruments cannot be light buckets with poor image quality. Specific engineering designs of large instruments should be undertaken to determine designs and costs associated with producing large instruments with image quality less than 2 see of arc. It is important that such instruments be built so that the field of infrared astronomy can be extended to the detection of fainter infrared sources. The question of optimum size of telescopes from the point of view of information gained per dollar is considered. If such a most economical size exists, it is certainly much larger than presently existing 1.5-m (60-in.) infrared telescopes.