“Minimum D” in the above photo means the inter-axis distance of the OTAs at the IPD of 60mm.
Two pairs of the EMS-UL SET in the making-2
MATSUMOTO-EMS | 天体望遠鏡革命
Innovation of Astronomical Telescope
正立ミラーシステム（EMS）を開発した松本龍郎のサイト。 たった２回の反射で天体望遠鏡の像を正立像にします。
Tatsuro Matsumoto; Inventor of the EMS, Erecting Mirror System. EMS offers non reversed upright image with no additional undesirable abberations.