PentaStar II
GemRay Brightness Plots for RI = 1.54
Random Model Cosine Model ISO Model
GemRay Brightness Plots for RI = 1.76
Random Model Cosine Model ISO Model
PentaStar II
designed by Bob Keller December 2001
A Cut Corner Pentagon with Crown Star
Angles for R.I. = 1.54 and up with medium color saturation 41 facets + 10 facets on girdle = 51
5-fold, mirror-image symmetry 80 index
L/W = 1.051 T/W = 0.337 T/L = 0.320 P/W = 0.465 C/W = 0.203 H/W = (P+C)/W+0.02 = 0.689 P/H = 0.676 C/H = 0.295
Vol./W^3 = 0.233 Brightness at 0° tilt RI = 1.54: COS = 76.4 ISO = 84.3
Brightness at 0° tilt RI = 1.76: COS = 76.7 ISO = 90.4
Pavilion
1 75.00 80-16-32-48-64 Cut to equal depth, match g1
2 46.00 08-24-40-56-72 Meet 1.g1.g2
3 41.50 04-12-20-28-36-44-52-60-68-76 Meet 1.g1.g2.2
Crown
a 43.00 80-16-32-48-64 Match g1, make upper girdle line
b 46.63 08-24-40-56-72 Meet a.g1.g2
c 32.45 80-16-32-48-64 Meet a.b.a
d 21.56 08-24-40-56-72 Meet c.a.b
t 0.00 Table Meet d.c.d

PentaStar II CAM Preform
pf1 45.00 80-16-32-48-64 Cut to equal depth, make temporary center point
g1 90.00 80-16-32-48-64 Match pf1, make level false girdle line
pf2 40.41 08-24-40-56-72 Meet at temporary center point
g2 90.00 08-24-40-56-72 Meet pf2.pf1.g1

The PentaStar II GemCad Design File and PentaStar II GemCad Preform Design File are available for GemCad users.


Index of Gem Designs

Perfect Transfer Index

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© Bob's Rock Shop Bob Keller