Lens system for astronomical telescope

摘要

The objective lens system for a telescope has a positive initial lens group (10) and a second lens group following sequentially from the object side. The second lens group has two lens subgroups. The first subgroup (20A) is for the correction of the axial chromatic aberration which can be combined with the first lens group (10). The second subgroup (20B) is for the correction of the image field curvature, and can be combined with the first lens group (10). The first lens group (10) can have alternative combinations with the two lens subgroups.