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Hi Logan
My experience is more with larger mirrors (18" f4), where you work with sub-diameter laps, so I'll share what I know:
More information is needed:
1. Have you polished enough? 4 hours is relatively short if polishing by hand.
2. Are you inside / outside focus? If you're inside focus, then you have some issues (use short strokes with small overhang slightly off-centre to lower the centre)
3. If you're outside focus, then it's not so much as a kink, but a spherical centre and some parabolisation towards from the 70% zone and you don't seem to have a TDE, which is good news! F2.8 is a pretty aggressive / short focal ratio. Check mel-bartels' website for the matching ronchigram to determine if you've over-parabolised the edge. If not, all you need to do is use a subdiameter lap (4") and parabolise the centre (short chordal strokes with minimal overhang close to COC), then smooth with full size lap.
Last edited by sfarndell; 12-11-2018 at 07:22 PM.
Reason: Inside / outside focus advice was muddled
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