[ATM] Explanation of the HCF lap effect (was Beeswax)
wa4guu at verizon.net
Sun Oct 11 05:20:06 JST 2009
The HCF lap pattern is quite small. The pattern is high frequency short
wavelength. The same pattern exits at all multiples of the wavelength. So
you have many sizes of the same pattern.
Try to pick a stroke length that is not the same length as one of the many
resulting larger patterns. It may be that the only change would be the
frequency of the resulting ripple.
On randomness: I have abandoned using the term "random" to describe what I
think is best termed as "variation".
Doing exactly the same length stroke across all diameters or chords of the
mirror is desirable. Randomness is not. Variation is desirable to prevent
sharp slope changes related to lap edge start/stop and lap pattern zones.
Variation is achieved by changing stroke length or offset after doing some
number of whole turns around the mirror. That variation will blur the
start/stop location of the lap edge, and facets.
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