Hi Polishers,
Very,very brief polishing, figuring log.(22" f5.36 mirror).
Time taken to polish to 99% : 7 hours. (14" lap #55 G and CeO).
Time figuring (first iteration) : 16.5 hours. (5", 8.5", 11", 14", 17" laps).
My method was to start the deepening towards parabola from the center out. Progress through lap sizes from smaller to larger, thus moving the correction outwards as lap size increased.
Noted: when the lap size was small, figure tended to rough and chaotic, but as lap size increased and correction moved out towards the mirror edge, figure began to smooth out and become less chaotic.
Have ended up, (for the first iteration, yet to be tried as an uncoated optic under the night sky). The figure is fairly smooth, (no high or low zones), a bit of TDE/rolled edge. Possibly a little over correction.
I have made two aperture masks, to give 1) 19" f6.21 (this takes out the edge defects, and should provide reasonable performance for solar system viewing). 2) 17.5" f6.74 ( experimental only). Am in process of making a 20.5" mask as well.(this may be sufficient to hide edge defect).
Currently figuring second 22" primary. Will take a similar time, but no appreciable edge defect at this point in time.
As for the first mirror: If it dosent perform , then another figuring iteration wil be in order.
Stephen.
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