A 20 m space telescope is described with an unvignetted 1° field of view—a hundred times larger in area than fields of existing space telescopes. Its diffraction-limited images are a hundred times sharper than from wide-field ground-based telescopes and extend over much if not all the field, 40 arcmin diameter at 500 nm wavelength, for example. The optical system yielding a 1°, 1.36 m diameter image at f/3.9 has relatively small central obscuration, 9% by area on axis, and is fully baffled. Several carousel-mounted instruments can each access directly the full image. The initial instrument complement includes a 400 gigapixel silicon imager with 2 µm pixels (0.005 arcsec), and a 60 gigapixel HgCdTe imager with 5 µm pixels (0.012 arcsec). A multi-object spectrograph with 10 000 fibres will allow spectroscopy with 0.02 arcsec resolution. Direct imaging and spectroscopy of exoplanets can take advantage of the un-aberrated, on-axis image (5 nm RMS wavefront error). While this telescope could be built for operation in free space, a site accessible to a human outpost at the Moon's south pole would be advantageous, for assembly and repairs. The lunar site would allow also for the installation of new instruments to keep up with evolving scientific priorities and advancing technology. Cooling to less than 100E K would be achieved with a surrounding cylindrical thermal shield. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

中文翻译：

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20 m 宽视场衍射极限望远镜

一个 20 m 的太空望远镜被描述为具有无渐晕的 1° 视场——面积比现有太空望远镜的视场大一百倍。它的衍射极限图像比宽视场地面望远镜的图像锐利一百倍，并且延伸到很多（如果不是全部）视场，例如，500 nm 波长下的直径为 40 弧分。在 f/3.9 下产生 1°、1.36 m 直径图像的光学系统具有相对较小的中心遮挡，轴上面积为 9%，并且完全被遮蔽。几个安装在转盘上的仪器可以直接访问完整图像。最初的仪器补充包括具有 2 µm 像素（0.005 弧秒）的 400 千兆像素硅成像仪和具有 5 µm 像素（0.012 弧秒）的 60 千兆像素 HgCdTe 成像仪。具有 10 000 根光纤的多目标光谱仪将允许光谱分辨率为 0.02 弧秒。系外行星的直接成像和光谱学可以利用无畸变的轴上图像（5 nm RMS 波前误差）。虽然这台望远镜可以建造用于在自由空间运行，但在月球南极的人类前哨可以进入的地点对于组装和维修来说将是有利的。月球站点还将允许安装新仪器，以跟上不断发展的科学重点和先进技术。冷却至低于 100E K 将通过周围的圆柱形隔热罩实现。这篇文章是讨论会问题“月球天文学：未来几十年”的一部分。在月球南极建立一个人类前哨可以进入的地点对于组装和维修来说是有利的。月球站点还将允许安装新仪器，以跟上不断发展的科学重点和先进技术。冷却至低于 100E K 将通过周围的圆柱形隔热罩实现。这篇文章是讨论会问题“月球天文学：未来几十年”的一部分。在月球南极建立一个人类前哨可以进入的地点对于组装和维修来说是有利的。月球站点还将允许安装新仪器，以跟上不断发展的科学重点和先进技术。冷却至低于 100E K 将通过周围的圆柱形隔热罩实现。这篇文章是讨论会问题“月球天文学：未来几十年”的一部分。