Azimuth Shift & Yaw

[beryl]

I have been trying to digest the lengthy thread started by Midnight; it seems to have digressed into a discussion of azimuth shift vs 'yaw'. I hope the following 3 illustrations will clarify this matter.
Fig.1 is a perfectly-cut 8-point round brilliant pavilion - with only 50% halves to exaggerate the effects. Scallops are omitted because they add a lot of drawing work but contribute little to the message.
Note the 'traces', which are the intersections between the facet planes and the plane of the girdle; these traces are oriented according to the azimuths used to cut the facets. Here I show the traces of the main facets, which form an octagon. The dotted lines from their intersections show that the main facets (red) would form a pyramid if the halves (blue) were missing.

 

[beryl]

Fig.2 shows what would happen if we cut a new facet at the same slope but with its azimuth shifted 3° - as if to remove a blemish. Note that the apex of the pyramid is the same but the original main has now become a double. Ony the most disinterested faceter would leave it this way.
The two red dots show the intersection of the new (red) trace with the adjoining ones, and thus the base of this face of the pyramid.

 

[beryl]

Fig.3 shows that we can achieve the left edge of the original facet by increasing the slope of the new one. Note that the red dot at the base of the facet has returned to its original position by moving the new trace inward (= making the facet steeper); thus the join line of the new main with the one to its left is the same as before. It is as though we had folded the surface along this line,
The red dot on the right, however, has moved also, making the facet much wider. The new facet now cuts severely into the existing halves; they must be recut to look 'proper', as shown by my illustration of 2005 Jan 22, shown in the other thread (page 2). Sadly it has undesirable effects on the girdle scallops (not shown here); the scallops produced by recutting these halves are much deeper than the others - 1% or more.
I think this is what Brian has chosen to call 'yaw' = keeping one side of the original facet. It is well-known to most faceters but I have never heard them use this term.

 

[Rhino]

Thanks for sharing this beryl. I''ve long since been a fan of your writing and if I''ve never made your acquaintance please allow me to do so now. I really find this stuff interesting and your illustrations really do a great job of making it easy to understand. My studies have primarily focused on things that affect the face up optical design of diamonds as observed through reflector scopes and how it correlates with other technologies but all of this helps complete the pieces of the puzzle. I realize there are many factors that can influence the optical design so I''m taking baby steps to learn how to decipher it all and your illustrations really help. If, in the other thread you see if there is any misunderstanding on my part please let me know as I''m interested in presenting honest and accurate info. I do have a .dmc file of the stone I posted a picture of which I''ve generated through the Helium software. I would appreciate it if you could analyze it for me and let me know your input. Drop me a pm and check off the email option and I can forward it to you as early as tomorrow if you would.

Kind regards,
Jonathan

 

[belle]

Date: 9/6/2005 8:49:22 PM
Author: beryl
Fig.3 shows that we can achieve the left edge of the original facet by increasing the slope of the new one. Note that the red dot at the base of the facet has returned to its original position by moving the new trace inward (= making the facet steeper); thus the join line of the new main with the one to its left is the same as before. It is as though we had folded the surface along this line,
The red dot on the right, however, has moved also, making the facet much wider. The new facet now cuts severely into the existing halves; they must be recut to look ''proper'', as shown by my illustration of 2005 Jan 22, shown in the other thread (page 2). Sadly it has undesirable effects on the girdle scallops (not shown here); the scallops pruduced by recutting these halves are much deeper than the others - 1% or more.
I think this is what Brian has chosen to call ''yaw'' = keeping one side of the original facet. It is well-known to most faceters but I have never heard them use this term.

here is the illustration bruce is referring to:

 

[beryl]

Rhino:
You were uppermost in my mind when I did this. You seemed to be mystified, with statements such as 'when is azimuth shift serious enough to be called yaw' (or words to that effect). I thought the answers you were getting were not clear enough without pictures; so here they are.
One of these Wednesdays I intend to depart from my wife at Mohegan Sun and take the ferry across to Massapequa to see you. I was going to surprise you, but any helpful hints you can provide will make the ttrip easier. Sorry I missed you in LasVegas; I had just returned from Antwerp and work was piled high at the shop.
I would not know what to do with a .dmc file; I am a computer klutz.
BTW; your buddy, Barry, is mad at me (in DiamondTalk).

 

[beryl]

Belle:
Thank you; I could not find that pic in my files.

 

[Rhino]

Date: 9/6/2005 9:48:05 PM
Author: beryl
Rhino:
You were uppermost in my mind when I did this. You seemed to be mystified, with statements such as ''when is azimuth shift serious enough to be called yaw'' (or words to that effect). I thought the answers you were getting were not clear enough without pictures; so here they are.
One of these Wednesdays I intend to depart from my wife at Mohegan Sun and take the ferry across to Massapequa to see you. I was going to surprise you, but any helpful hints you can provide will make the ttrip esier. Sorry I missed you in LasVegas; I had just returned from Antwerp and work was piled high at the shop.
I would not know what to do with a .dmc file; I am a computer klutz.
BTW; your buddy, Barry, is mad at me (in DiamondTalk).

Hey beryl,

Heh... when I saw this thread after mine I kinda knew I put more of this stuff on your brain. Didn''t mean to rack ya but while you''re here I have a couple of questions if you don''t mind. Also, please do not feel compelled to answer me quickly, I respect your time and the effort you put into your images so please, do not in any way feel rushed to answer me.

When talking about a facet you say has been yawed and its undesireable effects on the adjoining lower halves you say "Sadly it has undesirable effects on the girdle scallops (not shown here); the scallops pruduced by recutting these halves are much deeper than the others - 1% or more."

Are you saying the girdle thickness will generally always be thicker in that section where the azimuth deviations are taking place? In the graphic that bell posted which was in the other thread (btw thank you belle, you rock

) the shift in azimuth angles on the adjoining halves is 4.69 degrees east and 5.06 degrees west. THAT''S SEEMS LIKE A PRETTY SERIOUS DEVIATION. My question then to you would be... Do azimuth angles have to deviate to this degree to really cause girdle scallop problems or are these girdle scallop problems detectable when the deviation is more minimal?

I''m going to have to go check out the girdle graph of that stone and see now.

 

[Rhino]

Date: 9/6/2005 9:48:05 PM
Author: beryl
Rhino:

One of these Wednesdays I intend to depart from my wife at Mohegan Sun and take the ferry across to Massapequa to see you. I was going to surprise you, but any helpful hints you can provide will make the ttrip esier. Sorry I missed you in LasVegas; I had just returned from Antwerp and work was piled high at the shop.

Oops... forgot to answer your other comments.

Forgive but where is Mohegan Sun? Ct? If so I can give you easy directions. I would LOVE to have you here Bruce. I''ll show ya all the toys, introduce ya to the staff, let ya check out the new scanner and ASET. It''s stuff you may find interesting. There''s an awesome pizza place next door or there''s TGIF across the parking lot too.

Yea... sorry I missed ya in Vegas too. I also missed Wink and Marty too.

Next trip for me will have to be just a little longer.

I would not know what to do with a .dmc file; I am a computer klutz.
BTW; your buddy, Barry, is mad at me (in DiamondTalk).

If you make the trip here, as we''re chowin down I''ll show ya how to play with DiamCalc. It''s a cut geeks dream. hehe I''m still learning with it. Serg is tremendous help when I have questions too.

also... Barry is the antithesis of being my buddy.


Warm regards,

 

[beryl]

Quoting Rhino:
"When talking about a facet you say has been yawed and its undesireable effects on the adjoining lower halves you say "Sadly it has undesirable effects on the girdle scallops (not shown here); the scallops pruduced by recutting these halves are much deeper than the others - 1% or more."
"Are you saying the girdle thickness will generally always be thicker in that section where the azimuth deviations are taking place? In the graphic that bell posted which was in the other thread (btw thank you belle, you rock ) the shift in azimuth angles on the adjoining halves is 4.69 degrees east and 5.06 degrees west. THAT'S SEEMS LIKE A PRETTY SERIOUS DEVIATION. My question then to you would be... Do azimuth angles have to deviate to this degree to really cause girdle scallop problems or are these girdle scallop problems detectable when the deviation is more minimal?"
-----------------------------------------------------------------------------
As shown in the illustration Belle provided, recutting the halves makes the facets deeper. That example was absurd - exaggerated to illustrate the point. As John pointed out, the azimuth difference between the surfaces was only 11.25-4.82-5.06° = 1.37° = almost none; you could not polish two adjacent facets with this small difference - the join between them would round off and be indistinct.
The case of 3° azimuth shift illustrated here, in Fig.2 & 3, is also an exaggeration, as are the 50% halves. So I have exaggerated the effects on scallop depth - it may be insignificant with only 1° azimuth shift and 80% halves. I could calculate that but it takes time (next week at casino, perhaps).
I did a data-intensive article on crown girdle scallop twisting in PriceScope late April 2004; you might want to check that out. We were all on the way to Moscow for IDCC, so little discussion followed. Peter Yantzer has since discussed the same thing in less technical terms.
This AM I find a message from Brian saying I've got it wrong - that I have diverged from our understanding of what he calls 'yaw', and have confused the issue. But look at the illustration he 'copyrighted' - same thing. What I have shown in Fig.3 (and on Jan 22) is something well-known to all faceters; perhaps it is not 'Gavin's Yaw' but you can add it to your cutting knowlege anyway.

 

[denverappraiser]

All of these discussions seem to include the assumption that each facet is a single planar surface. Is this necessarily true? I can’t say I have any idea how to cut a slightly domed, twisted or even concave facet but it seems theoretically possible and it would have a tremendous affect on this issue. Is this possible and is it ever done?

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[Rhino]

Date: 9/7/2005 7:06:16 AM
Author: beryl

Quoting Rhino:
''When talking about a facet you say has been yawed and its undesireable effects on the adjoining lower halves you say ''Sadly it has undesirable effects on the girdle scallops (not shown here); the scallops pruduced by recutting these halves are much deeper than the others - 1% or more.''
''Are you saying the girdle thickness will generally always be thicker in that section where the azimuth deviations are taking place? In the graphic that bell posted which was in the other thread (btw thank you belle, you rock ) the shift in azimuth angles on the adjoining halves is 4.69 degrees east and 5.06 degrees west. THAT''S SEEMS LIKE A PRETTY SERIOUS DEVIATION. My question then to you would be... Do azimuth angles have to deviate to this degree to really cause girdle scallop problems or are these girdle scallop problems detectable when the deviation is more minimal?''
-----------------------------------------------------------------------------
As shown in the illustration Belle provided, recutting the halves makes the facets deeper. That example was absurd - exaggerated to illustrate the point. As John pointed out, the azimuth difference between the surfaces was only 11.25-4.82-5.06° = 1.37° = almost none; you could not polish two adjacent facets with this small difference - the join between them would round off and be indistinct.
The case of 3° azimuth shift illustrated here, in Fig.2 & 3, is also an exaggeration, as are the 50% halves. So I have exaggerated the effects on scallop depth - it may be insignificant with only 1° azimuth shift and 80% halves. I could calculate that but it takes time (next week at casino, perhaps).
I did a data-intensive article on crown girdle scallop twisting in PriceScope late April 2004; you might want to check that out. We were all on the way to Moscow for IDCC, so little discussion followed. Peter Yantzer has since discussed the same thing in less technical terms.
This AM I find a message from Brian saying I''ve got it wrong - that I have diverged from our understanding of what he calls ''yaw'', and have confused the issue. But look at the illustration he ''copyrighted'' - same thing. What I have shown in Fig.3 (and on Jan 22) is something well-known to all faceters; perhaps it is not ''Gavin''s Yaw'' but you can add it to your cutting knowlege anyway.

Thanks for clarifying beryl. Hehe... knowing Brian''s response to you I''m glad to see that I''m not alone in any misunderstanding I may have of that subjet. For the time being I"m going to stick with observations in azimuth shift since we have the ability to measure that. Baby steps. Nice weather we''re getting up here eh?

 

[beryl]

Date: 9/7/2005 7:48:02 AM
Author: denverappraiser

All of these discussions seem to include the assumption that each facet is a single planar surface. Is this necessarily true? I can’t say I have any idea how to cut a slightly domed, twisted or even concave facet but it seems theoretically possible and it would have a tremendous affect on this issue. Is this possible and is it ever done?

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

Mr. Beaty:
Both convex and concave facets exist. Convex facets occur commonly (but not intentionally) by polishing too fast or with too much abrasive on the lap (flows under the leading edge). 30 years ago, I heard of one mass-production cutting firm used large cylindrical laps on their automatic faceting machines; this offset the convex tendency of cutting too fast and thus gave them nearly-flat facets
Glenn Vargas tells me that rounded edges are common on Brazilian native-cut stones because they bring one side of the facet down onto the lap and then flop it flat - forming a rolled edge on one side of each facet.
Also, some Mexican-cut stones, I am told, get their final polish in a tumbler, which rounds all edges.
Watch the stones rotate in the light on a TV jewelry-selling show; you can often see the reflections move across the facets, rather than snap on-and-off; this indicates curved surfaces.
Concave facets are relatively new. There is a machine now which cuts only concave facets; they call it 'OMF' = 'Optical Magnifying Facets'. Wink, a common contributor to DiamondTalk (then) and PriceScope (now), has often raved about a faceter-friend of his who does this.
I tell new faceters that one of the 3 most important factors in faceting is flatness of facets - that's what makes the reflections snap on and off = best 'dynamic contrast' or 'scintillation'.

 

[denverappraiser]

Thanks Bruce,

I've seen both concave and convex faceting on softer stones but I don't recall ever seeing this done with diamonds. It seemed relevant to this discussion of Yaw and Azmuth. Is there a way to cut a facet with a twist? Thanks for the insights.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[beryl]

Mr.Beaty:
Good point - all of my discussion pertains to colored stones; I have never seen either feature on diamonds. Also, I have never seen twisted facets on anything, nor can I think immediately of a practical way to do it.
Bruce Harding

 

[belle]

very interesting....thank you for bringing that to light neil.

 

[beryl]

Mr. Beaty:
I forgot to mention ''buff-tops'' which are gems with faceted pavilion and cabochon top - colored stones only. They are interesting but not as nice as a fully-faceted stone. In my ray-tracing program (1986) I simulated this by using a step-cut top with many small steps; I haven''t tried it with the new software.

 

[beryl]

Rhino:
I have determined the amount of drop in girdle scallop tip for a more realistic example.
For a pavilion with 40.75° main slope and 80% halves, with 1° azimuth shift and associated slope increase of main and recutting of 3 break facets - as in my pic of Jan 22 - the drop would be 0.31% (of girdle width) = quite small.

Edit: 4:00 PM: Depth of the normal scallop in this case is 0.84%* - from tip at girdle line to bottom of scallop below girdle line at its mid-point. The modified cutting described above has dropped the tip of the scallop 0.31% = 3/8 the depth of the normal scallop, which will also lower the bottom of the adjoining scallops - perhaps about 0.25% lower than the other scallops. This should be visible on a large stone. Diagrams may follow to help illustrate what I am saying. You can see it in the illustration of Jan 22, which Belle provided.
I wrote a detailed article on scallops in DiamondTalk 3 years ago - threadid=23362 11-14-02. For a Tolkowsky diamond it showed scallop depth of 0.86% at the pavilion and 0.83% at the crown = 1.7% total difference between thick and thin parts of the scallops at the girdle. If you start with a girdle where the scallops are only 1% thick at the thinnest point (= 2.7% thick at the tips of the mains) then this deviation of 0.25% should be noticeble = 1/4 of the thinnest girdle at other points.
In that article I also showed the geometric effects of shifting azimuth with various index wheels, producing alternately thick-and-thin points of the scallops - which Peter Yantzer and GIA have written about since. At that time Garry had asked me about this effect in relation to 'clicks'; he had noticed it on 8-Star diamonds and had heard the term 'click'. I was only pointing-out that these effects were finer than you would be likely to produce with a click of a standard index wheel. This requires associated change in slope of the break facets (which diamantaires call 'halves') but not the mains, which is different than what I illustrated in my pic of Jan 22 2005.
Pretty bad when the edit is bigger than the post - I was 'flying' this AM to get to work on time.

* Edit 9:30 PM: Depth is 0.86%, not 0.84%

 

[Garry H (Cut Nut)]

Using the latest version of DiamCalc, I can make a very big diamond, and shift its azimuth by 1% each way - and I get 2 different % variations.

3.06257495% when we make the half junction thicker (+1%)
3.031178% when we make the main facet junction thicker (-1%)

Does that seem correct Bruce?

 

[beryl]

Date: 9/9/2005 9:24:50 AM
Author: Garry H (Cut Nut)
Using the latest version of DiamCalc, I can make a very big diamond, and shift its azimuth by 1% each way - and I get 2 different % variations.

3.06257495% when we make the half junction thicker (+1%)
3.031178% when we make the main facet junction thicker (-1%)

Does that seem correct Bruce?

I cannot comment without a picture to clarify your terminology, but it sounds like you are reading the numbers 1 decimal point too large. 3% is 0.03, not 0.003, which is what I get per my description. I will try to provide some meaningful illustrations. Perhaps you will do likewise.

 

[Rhino]

Date: 9/9/2005 7:26:59 AM
Author: beryl
Rhino:
I have determined the mount of drop in girdle scallop tip for a more realistic example.
For a pavilion with 40.75° main slope and 80% halves, with 1° azimuth shift and associated slope increase of main and recutting of 3 break facets - as in my pic of Jan 22 - the drop would be 0.31% (of girdle width) = quite small.

Edit: 4:00 PM: Depth of the normal scallop in this case is 0.84% - from tip at girdle line to bottom of scallop below girdle line at its mid-point. The modified cutting described above has dropped the tip of the scallop 0.31% = 3/8 the depth of the normal scallop, which will also lower the bottom of the adjoining scallops - perhaps about 0.25% lower than the other scallops. This should be visible on a large stone. Diagrams may follow to help illustrate what I am saying. You can see it in the illustration of Jan 22, which Belle provided.
I wrote a detailed article on scallops in DiamondTalk 3 years ago - threadid=23362 11-14-02. For a Tolkowsky diamond it showed scallop depth of 0.86% at the pavilion and 0.83% at the crown = 1.7% total difference between thick and thin parts of the scallops at the girdle. If you start with a girdle where the scallops are only 1% thick at the thinnest point (= 2.7% thick at the tips of the mains) then this deviation of 0.25% should be noticeble = 1/4 of the thinnest girdle at other points.
In that article I also showed the geometric effects of shifting azimuth with various index wheels, producing alternately thick-and-thin points of the scallops - which Peter Yantzer and GIA have written about since. At that time Garry had asked me about this effect in relation to 'clicks'; he had noticed it on 8-Star diamonds and had heard the term 'click'. I was only pointing-out that these effects were finer than you would be likewly to produce with a click of a standard index wheel. This requires associated change in slope of the break facets (which diamantaires call 'halves') but not the mains, which is different than what I illustrated in my pic of Jan 22 2005.
Pretty bad when the edit is bigger than the post - I was 'flying' this AM to get to work on time.

Hey beryl,

Just caught this. THANKS! When I get up to the lab tomorrow I'm going to study some examples I have with azimuth shift and study the girdles at those points. The stone I posted recently as photographing the shift in azimuth angles through the crown had a shift of 1.27 degrees west. So this is pretty close to what you're talking about above. I'll show you what I discover, if anything.

BTW ... is Mohegan Sun in CT.?

 

[Garry H (Cut Nut)]

Date: 9/9/2005 4:25:43 PM
Author: beryl

Date: 9/9/2005 9:24:50 AM
Author: Garry H (Cut Nut)
Using the latest version of DiamCalc, I can make a very big diamond, and shift its azimuth by 1% each way - and I get 2 different % variations.

3.06257495% when we make the half junction thicker (+1%)
3.031178% when we make the main facet junction thicker (-1%)

Does that seem correct Bruce?

I cannot comment without a picture to clarify your terminology, but it sounds like you are reading the numbers 1 decimal point too large. 3% is 0.03, not 0.003, which is what I get per my description. I will try to provide some meaningful illustrations. Perhaps you will do likewise.

Of course you are correct Bruce
0.306257495% when we make the half junction thicker (+1%)
0.31178% when we make the main facet junction thicker (-1%)
This stone has had the upper girdle painted - it is indexed to 10.25 degrees instead of the normal 11.25 degrees

 

[Rhino]

Garry,

I notice on the Helium Reports, in the summary up top it describes what "girdle type" the diamond has. On stones that you and I know as painted, Helium says "digging, gouging". Isn't digging (gouging) the opposite of painting?

 

[beryl]

I finished the diagram I started this AM. Here it is; not very fancy but adequate.
Note that the depth of the standard scallop (for 40.75° mains and 80% halves) is 0.86%, as I reported in DiamondTalk article of 2002 (the 0.84% I cited in my edit tonight was incorrect). The deepest point of the modified scallops is 1.03% = only 0.17% deeper, not the 0.25% deeper I had guessed. These two dim's are shown on the diagram. The tip of the mongrel main is 0.31% below the girdle line (red - does not show well - perhaps I will provide a closer view).
Looking at this picture I have to chuckle - the 'mains' are not the main facets anymore. As an aside, I like shorter mains for better contrast action, sacrificing some brilliance = more 'attractive' to my eye.

Edit 10:15 PM: Looking at the total picture I think you would not notice that it is deformed. Without instruments, the girdle scallops might be a clue, but they often vary for a variety of reasons - too many to be a reliable indication of anything.
Brian and Paul are worried about whether Sarin, Ogi, etc, measure the true slope of the facet = sighting parallel to the shifted 'trace' (azimuth). I would need to know more about how these machines measure to comment precisely. If the machine instead sights the profile of the facet edge at the expected azimuth, that reading will not be the true slope of the facet; however, the error would be so infinitesimal that it would not matter = a 'non-problem'.
Rhino: Mohegan Sun is one of the 2 large casinos in Connecticut, near the coast; many players come over from Long Island by ferry and tell me Massapequa is not far. Evelyn and I are there most Wednesdays. I gamble for an hour and spend the rest of the day working in the Food Court. This is where I translate Russian articles and now do stuff with a laptop computer. Blackjack paid for my trip to the IDCC Conference in Moscow last year.

 

[beryl]

Here's a blowup of the area in question. The upper red line is the pavilion girdle line, which passes through the tips of the normal mains and their scallops. The lower red line is shown 1% away from the 'bottom' of the normal scallops, which is where the 'bottom' of the crown scallops would be if you had a stone with 1% girdles at the thin points between normal scallops. I just added this to see if the difference in thickness would be noticeable; I think it is not.
In this enlargement I have also shown the 0.31% that the tip of the mongrel main is below its proper level at the upper red girdle line.

 

[beryl]

Date: 9/9/2005 8:47:53 PM
Author: Garry H (Cut Nut)

Date: 9/9/2005 4:25:43 PM
Author: beryl

Date: 9/9/2005 9:24:50 AM
Author: Garry H (Cut Nut)
Using the latest version of DiamCalc, I can make a very big diamond, and shift its azimuth by 1% each way - and I get 2 different % variations.

3.06257495% when we make the half junction thicker (+1%)
3.031178% when we make the main facet junction thicker (-1%)

Does that seem correct Bruce?

I cannot comment without a picture to clarify your terminology, but it sounds like you are reading the numbers 1 decimal point too large. 3% is 0.03, not 0.003, which is what I get per my description. I will try to provide some meaningful illustrations. Perhaps you will do likewise.

Of course you are correct Bruce
0.306257495% when we make the half junction thicker (+1%)
0.31178% when we make the main facet junction thicker (-1%)
This stone has had the upper girdle painted - it is indexed to 10.25 degrees instead of the normal 11.25 degrees

Garry:
I was hoping that this ''quote'' would copy your illustration. I think that what you have done is to shift a ''half'' facet 1°. This is like my DiamondTalk thread of Nov 11, 2002. It is coincidental that you also get a value of 0.31% (your 9-significant-figure answer is humorous).
In my example of Fig.7 the main is shifted 1°, and must be steepened from 40.75° to 40.96° to avoid the double-main situation (as shown exaggerated in my Fig.2 & 3). I think this is what Brian means by the term ''yaw''. This drops its interception of the girdle circle 0.0031 = 0.31% at the same point of the circle (an even bigger blowup will show this alignment).
Halves ''A'' and ''B'' are then twisted and tilted to form a 3-facet meet at this point, and halves ''B'' and ''C'' are adjusted to bring their meet at the other end to the 80% point (''upper'' end in this pic). There are infinite fixes for this twisted and tilted main; I chose this one which most resembles an ideally-cut stone.
Sorry for all this complexity in description (I have to anticipate the ''snipers'' out there who will jump on any inaccuracy or ambiguity). It''s so much easier to do it - a flick of the wrist and a blink of an eye.

 

[Garry H (Cut Nut)]

Caught red handed.
I did not read the thread.
Sorry
(but it was a strange coincidence)

 

[beryl]

Garry: How can you comment on what you don''t read? That is a real puzzle.
Here is the bigger blowup I suggested; note the vertical alignment of the adjusted main tip (bold line) directly below the ideal one (fine line). This is not necessary but a choice I made to make the modified stone look as much as possible like the ideal.

 

[Rhino]

Heh... that''s cause Garry probably responded after having a little vino.

Hi beryl. I''ve went over the girdle graph and model of a stone I''ve been looking at with azimuth deviation and couldn''t note anything of major importance. I realize you''re splitting frog hairs here so perhaps I''m not looking closely enough? I can post the model of the girdle in that region where the azimuth shift occurs, blown up, if you think that would help.

 

[Garry H (Cut Nut)]

Date: 9/10/2005 8:11:48 PM
Author: Rhino
Heh... that''s cause Garry probably responded after having a little vino.

You''r on the money Rhino
it was late Friday night after our traditional Japanese dinner with friends