Does Protostar sell “1/30 wave” flats?
Despite outlandish claims, a 1/30 wave peak-to-valley surface from edge-to-edge is exceedingly rare. It’s impractical to even test a surface accurately to this level. A $75,000 Zygo interferometer has its 100mm reference element rated at 1/20th, so even measuring beyond this level of accuracy is difficult in itself. Protostar flats are tested edge-to-edge across the entire surface (i.e., no edge masking, or “trimming”). In many cases, much of the surface error is near the edge, so our method gives the most conservative number. Unlike many optics, a Newtonian secondary mirror is frequently optically active across its full aperture, so this is how the optic should be measured.
