a Light Shroud?
A light shroud is an optical tube
cover that blocks light from entering the light path within the
telescope. Shrouds are usually used for open truss tube telescopes
that are otherwise open to stray light. These scopes are designed
with truss rods, rather than a solid tube, to make them as lightweight as
are made of 100% cotton interlock material with elastic bands. This
material allows the shroud to stretch some in both directions for a
perfect fit. Heavy dew beads up on the outside rather than soaking
into the material and can easily be "snapped" off.
additional benefit of using a shroud is protection of the primary mirror
from dust and debris.