So there’s clearly positives and negatives. After reading the link that talks about the fan drawing air out of the back which helps remove the boundary layer off the front of the mirror I have a greater understanding of the need for air flow rather than just a cooling of the mirror glass. As far as stray light goes though we have to compare apples with apples. A truss telescope wouldn’t be great in light polluted skies one would imagine, and to the same effect open rear cells in dark or at least darker skies aren’t going to be affected in the same way they “ might “ in High LP skies. All good food for thought
