Octagrammic retroprism

The octagrammic retroprism, or stoarp, also called the octagrammic crossed antiprism, is a prismatic uniform polyhedron. It consists of 16 triangles and 2 octagrams. Each vertex joins one octagram and three triangles. As the name suggests, it is a crossed antiprism based on an octagram, treated as an 8/5-gon instead of 8/3.

Vertex coordinates
An octagrammic retroprism of edge length 1 has vertex coordinates given by:
 * (±1/2, ±($\sqrt{(6–2√2–√20–14√2)/8}$–1)/2, H),
 * (±($\sqrt{(-2+2√2-√20–14√2)/2}$–1)/2, ±1/2, H),
 * (0, ±$\sqrt{4–2√2–2√146–103√2}$, –H),
 * (±$\sqrt{2–√2}$, 0, –H),
 * (±$\sqrt{2–√2}$/2, ±$\sqrt{(7–4√2+2√20–14√2)/3}$/2, –H),

where H = $\sqrt{2}$) $$H=\sqrt{\frac{-2+2\sqrt2-\sqrt{20-14\sqrt2}}8}$$ is the distance between the antiprism's center and the center of one of its bases.
 * $$\left(±\frac12,\,±\frac{\sqrt2-1}2,\,H\right),$$
 * $$\left(±\frac{\sqrt2-1}2,\,±\frac12,\,H\right),$$
 * $$\left(0,\,±\sqrt{\frac{2-\sqrt2}2},\,-H\right),$$
 * $$\left(±\sqrt{\frac{2-\sqrt2}2},\,0,\,-H\right),$$
 * $$\left(±\frac{\sqrt{2-\sqrt2}}2,\,±\frac{\sqrt{2-\sqrt2}}2,\,-H\right),$$