Calculating Crown angles from Crown Height

[kevinraja]

If I know the crown height for an EC stone, how would I calculate the crown angles? Similarly, if I know the pavilion depth, how would i calculate pavilion angle?

For the following depth, table, crown height, pavilion height measurements, what would be the crown and pavilion angles. How would one calculate the angles since it could be different along the length and width and at corners?

8.36 x 6.11 x 3.87 Emerald cut
Table: 61%
Depth: 63.3%
Crown Height: 10.7%
Pavilion Depth: 51%

 

[belle]

the angles are measured by a sarin or ogi machine. they are all slightly different measurements, but should be *very* close as to achieve symmetry.

 

[kevinraja]

Based on the crown height and pavilion depth, I calculated the average crown angle to be 28.58 degrees and average pavilion depth to be 45.56 degrees. But the sarin reports says that the crown angle is 30.9 degrees and pavilion angle is 56 degrees. It looks like the SARIN is calculating angles based on the first step cut from the girdle.

Depth: 63.3
Table: 61
Crown height:10.7%
Pavilion Depth: 51%
Crown Angle: 30.9 degrees
Pavilion Angle: 56 degrees

 

[valeria101]

Date: 1/7/2005 9:589 PM
Author: kevinraja

It looks like the SARIN is calculating angles based on the first step cut from the girdle.

... and ther''s one more: these angles do not have to be the same on both the short and the long side of the stone. If these are averages, there is no way to know what the actual values were. The length of the keel and shape of corners allow some better guess, but by the time all is said and done, still one IS image comes closer to the truth, IMO.

Trying to recostruct step cuts by Sarin is kind''a depressing, IMO.

 

[Garry H (Cut Nut)]

Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong Wrong wrong

Emerald cuts do not even all have the same number of crown facets. They may have two steps = 2 angles or they may have 5-= 5 different angles.

Sarin and Ogi do not (yes I mean do not) measure these angles.

And even if they did - the complexxxxxity is too great for any effective interpretation.

The only way is to do a 3D scan and analyze the resultant 3D model. Ogi can not do that with DiamCalc software. They have some very basic software, as does Sarin, which is being half heartidly marketed as providing some solutions - but I have yet to hear of anyone taking it seriously - even inside those companies.