According to Agena-Astro the GSO secondaries are rated at 1/12 wave RMS.
https://agenaastro.com/gso-elliptica...ror-88-mm.html
Quote
"
GSO uses high-volume, state-of-the-art, high quality manufacturing and test lines. GSO guarantees diffraction limited performance, but their secondary mirrors typically have a mirror surface quality of 1/12 wave RMS at least, and often better. This very smooth mirror surface results in excellent optical performance with practically no light scatter."
EDIT: Not sure how you convert RMS to Peak - Valley, but if its like AC theory then 1 Volt RMS = 2.828V Peak to Peak, which would make it approx 1/4 wave peak to valley??
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Anyway for prime focus imaging which is at the lowest magnification the Newtonian scope can provide, I don't think you need 1/30 wave spec's unless you also intend to use it for high magnification visual.