John B (ausastronomer) delivers rare informed insight yet again. Listen to him. The large secondary will indeed be a problem for high powers. I've only ever looked through one astrograph, but my limited experience correlates with optical theory that it's basically a difficult to control blackout effect that is no issue for a camera sensor because you position it precisely at the focal plane, but for visual you can't help your head moving back-and-fro and side-to-side a little, and a large SO will be an intolerable annoyance at mid-high powers.
LVW 22mm discontinued? Oh no!
http://astroshop.com.au still have it listed...? It's a great EP, one of the best.