Amici prisms are extremely useful for daylight use because of the erect and side-correct images, but can help a lot during nighttime observations to find objects with general-purpose charts. Image quality is not as high as for diagonals because of the more complicated internal light paths, so using them for high-magnification astronomical observations is not recommended.
However these ones provide good image quality compared to department store ones. The 45 degree version is useful when looking objects close to the horizon, while the 90 degree version is more comfortable when it is needed to look upwards.
The 1.25\" nose offers standard filter thread for neutral density, polarizing or colour filters.