An all-spherical catadioptic system made of glass of one type is proposed for the monitoring of large sky areas. We provide an example of such a system with the aperture of diameter 400 mm and the curved field of 30 degree in diameter.
@article{arxiv.1507.07110,
title = {All-spherical telescope with extremely wide field of view},
author = {V. Yu. Terebizh},
journal= {arXiv preprint arXiv:1507.07110},
year = {2015}
}