[skysurfer]

I have an Amici prism for my small 8cm telescope and sometimes I use it with my Televie Genesis to avoid mirror images to compare it easily with star charts.
A 'normal' diagonal has only one reflecting surface, an Amici two and binoculars have four. In the latter two cases prisms are used which also add one extra glass-air transition with light loss. Although modern higher end multicoated prisms have light loss of no more than 1%, every % is one too much.
Better quality normal diagonals as the one in my Genesis are mirrors not prisms. And in SLRs the same: high end cameras such as the Nikon D4, D800 or Canon EOS 5 and 1 have a pentamirror instead of a pentaprism.
But there is no such thing as am 'Amici mirror', i.e. two 45 degree mirrors which make the image erect over a 45º or 90º viewing angle.
My questions:
- why is there no market for an Amici mirror as technically it is possible ?
- why do binoculars not use mirrors as 4 mirrors have less light loss than 4 prisms ?
- why do binoculars with 90º viewing angle not use Amici prisms (or mirrors) ? Less weight and light loss.

No I don't like prisms particularly not PRISM.