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## Origin of the origin in the International Tables Diagrams

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 ```Date: Thu, 02 May 2002 19:21:20 Newsgroup: sci.techniques.xtallography Subject: International Tables Diagrams From: James Silverton [jim.silverton@erols.com] Newsgroups: sci.techniques.xtallography Someone just asked me why the space group diagrams in the Tables have the origin at the top left corner of the page. I have a vague feeling that someone once told me but I cannot remember. Does anyone know? TIA, Jim. -- James V. Silverton Potomac, Maryland.```

 ```Date: Fri, 03 May 2002 16:41:57 Newsgroup: sci.techniques.xtallography Subject: Re: International Tables Diagrams From: Mike Glazer [glazer@physics.ox.ac.uk] At: Oxford University, England There are two answers to this as far as I can see: 1. If they put the origin somewhere else then you would legitimately write and ask why there? It's there because it's there! 2. It is convenient to use the top left corner because with a right-handed choice of axes one has a down the page, b to the right and c out of the page. Thus by putting the origin at the top left we have the three positive axes a b and c coming from this origin across and down the page. Mike Glazer Oxford ```

 ```Date: Fri, 03 May 2002 19:37:48 Newsgroup: sci.techniques.xtallography Subject: Re: International Tables Diagrams From: James Silverton [jim.silverton@erols.com] Mike Glazer wrote: > > There are two answers to this as far as I can see: > 1. If they put the origin somewhere else then you would legitimately write > and ask why there? It's there because it's there! > 2. It is convenient to use the top left corner because with a right-handed > choice of axes one has a down the page, b to the right and c out of the > page. Thus by putting the origin at the top left we have the three positive > axes a b and c coming from this origin across and down the page. > > Mike Glazer > Oxford > > "James Silverton" wrote in message > news:3CD183A0.D39A9E68@erols.com... > > Someone just asked me why the space group diagrams in the Tables have > > the origin at the top left corner of the page. I have a vague feeling > > that someone once told me but I cannot remember. Does anyone know? Thanks for the reply Mike. Of course, ultimately the question is unimportant apart from historical interest but I have never accepted "because it is" as an answer :-). However, the original questioner felt that the system was contrary to the normal way of drawing a graph with the origin at the lower left. I'm afraid that I don't see the arguments about convenience since the origin could be placed at the lower left with a 90 degree rotation of the picture without doing violence to the handedness. I don't have a copy of Kathleen Lonsdale's first version of the Tables but was it perhaps her choice? By no means all books on crystallography follow the Tables. Best wishes, Jim. -- James V. Silverton Potomac, Maryland.```

 ```Subject: Re: International Tables Diagrams Date: Mon, 6 May 2002 10:16:16 +0100 From: "Mike Glazer" [glazer@physics.ox.ac.uk] Organization: Oxford University, England Newsgroups: sci.techniques.xtallography The structure factor tables of Kathleen Lonsdale were without diagrams. She does mention in her introduction that choices of origins etc were made by Wyckoff and are also given in the Internationale Tabellen Vol 1. 1935. In this latter volume (which I also have) the chapter on space groups is by Astbury, Mauguin, Hermann, Niggli, Brandenberger and Lonsdale (ne Yardley). In the introduction they describe the current choice of origin as being in the top left. They also say "The representation rests principally on Schiebold's atlas (which I do not have!) along with certain modifications linking up with those due to Astbury and Yardley(Lonsdale)." The earlier tables of Astbury and Yardley were published in Phil. Trans. Roy. Soc, A224 (1924) but I have not had time to go and read this. By the way, funnily enough the standard choice of origin for graphics in computer screens is at the top left too! Mike Glazer Oxford```

 ```Subject: Re: International Tables Diagrams Date: Mon, 6 May 2002 12:55:16 +0100 From: Harry Powell [hrp1000@cam.ac.uk] Organization: University of Cambridge, England Newsgroups: sci.techniques.xtallography Hi Two other commonly encountered places where the top left is the origin chosen are books (and other printed organs) using the Latin and Cyrillic alphabets and the raster for VDUs (e.g. television, comuter displays...). You're probably reading this using an application that sets the origin at the top left... > By the way, funnily enough the standard choice of origin for graphics in > computer screens is at the top left too! Harry -- Dr Harry Powell, MRC Laboratory of Molecular Biology, MRC Centre, Hills Road, Cambridge, CB2 2QH See http://www.mrc-lmb.cam.ac.uk/harry for Mosflm, BCA and crystal growing details```

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