 Single-projector mirror systems, pioneered by Mirrordome from Swinburne, but now offered by a plethora of manufacturers, are placed on the edge of the dome to increase seating, decrease costs, and to allow analog planetariums to become digital without giving up their star projector.It is also possible to build such a system at relatively low cost.The main disadvantage is noticeably lower projection quality compared to purpose-built lenses, despite being able to project a higher proportion of the projector resolution.