math question for experts

[lulu]

If you have all the other measurements on a RB,including pavilion depth,is it possible to calculate pavilion angle,or should I just put my slide rule away?

 

[gnojham]

im no diamond expert (as we all know), but im pretty good with math
in my semi expert math opinion, id say you can definitely determine the pavillion angle as long as you have the other necessary measurements and percentages
you will need to know the diameter and pavillion depth to calculate the pavillion angle

 

[lulu]

I have diameter and pavillion depth-but what would the formula be?

 

[gnojham]

I have diameter and pavillion depth-but what would the formula be?



lulu

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youll need a calculator with a tan-1 function

divide one half the diameter by the pavillion depth
press the tan-1
add that number to 90 and subtract from 180

or!!!!!
divide the pavillion depth by one half the diameter
press the tan-1

i always like to do things the hard way

 

[gnojham]

did you do it?

 

[niceice]

One thing to keep in mind is that estimating a crown or pavilion angle is never as accurate as actually measuring the diamond on a Sarin or OGI machine... As far as the pavilion depth percent measurement goes, the Sarin and OGI machines actually measure the crown and pavilion angle measurements and then estimate the depth percent measurements based on those and the other measurements of the diamond... Therefore when you are estimating the pavilion angle based upon the pavilion depth percent you will actually be basing your estimate upon another estimate

 

[pricescope]

Assuming there is no culet, Pa=ATAN(Pd/50), where Pa is pavilion angle and Pd is pavilion depth %.

However, as Niceice noticed, if Pd is measured with an error, Pa will not be accurate either.

 

[lulu]

Sorry,just got back to my office and saw responses.Thanks
very much for the info.I don't have a calculator with a
tan function. Measurements are 7.3-7.35-6.5 and pavillion depth is 44. Can you calculate it from that?

 

[gnojham]

41.347

 

[Rank Amateur]

I would think that the point on the girdle at which the pav depth is measured plays a big role in determinng that pav angle.

Especially if you want the angle to three decimal places!

R/A

 

[69gm]

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On 8/6/2003 12:58:16 AM niceice wrote:

One thing to keep in mind is that estimating a crown or pavilion angle is never as accurate as actually measuring the diamond on a Sarin or OGI machine... As far as the pavilion depth percent measurement goes, the Sarin and OGI machines actually measure the crown and pavilion angle measurements and then estimate the depth percent measurements based on those and the other measurements of the diamond... Therefore when you are estimating the pavilion angle based upon the pavilion depth percent you will actually be basing your estimate upon another estimate

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also, according to people like dave atlas, neither the sarin nor the ogi are 100% accurate. in fact he said when taking measurements, the results would not always come out the same. of the 2, sarin is supposed to be more accurate with angles though.

 

[lulu]

Thanks for all the info and calculations-I appreciate it