The Nautilus is essentially the same as the Poseidon and It has the same EBC coating giving it excellent light transmission. It is slightly lighter in weight at 2.9 lbs. (3.0 lbs with compass). The eye relief is also greater at 16mm, which is at the top of the normal range for most binoculars. The compass model features a large, stable and accurate compass and reticle. The binoculars come with attached lens caps. A comfortable padded neck strap is an optional accessory. SW 4 lbs.