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HCA chart queston for GARY

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in_need_of_help

Shiny_Rock
Joined
Oct 30, 2003
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103
Hello Gary,

I just wanted to ask you a few questions about how to read your HCA chart. I understand following the x-axis for crown angles and following the y-axis for pavilion angles.

Sorry all, I could not figure out to attach the file. I kept on getting error messages. If someone else knows how to please do so.

My question is about the five lines (3 white, 1 green, and 1 black). What exactly do the color-coded lines refer to?

The upper and lower white lines do not appear to be boundaries because it includes HCA score greater than 2 and excludes HCA scores less than 2.

Thanks!
 

in_need_of_help

Shiny_Rock
Joined
Oct 30, 2003
Messages
103
Thanks Mara!


Gary, here is the HCA chart that I was referring to.

hca_question_zz.jpg
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
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18,418
OK
the 2 big white lines are taken from the gIA Fire study - they are ridges of higher dispersion.
The middle white line is their brilliance ridge - more brilliance at the upper left end.
The black line is a reworked (Jasper Paulsen) Tolkowsky using the same formula for varying crona nd pavilion angles.

The green is my best fit for the earliest MSU OctoNus Russian "Q" combined fire and light return.

The point is that there is a genaral agreement in principle that there is a relationship between crown and pavilion angle that 'spreads' an ideal cut to a range rather than a single set of numbers.
 
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