Re: Azimuthal sundials - again
Hi Steve: Your interpretation of the various dial classifications seems to be correct, although I'm certainly not an expert, as you know! Reading your letter, which was written so clearly, gave me confidence that I had interpreted the discussion correctly. Thanks, John C. Gianni wrote: The Monofilar and Bifilar sundials can be built with any kind of Time: Middle Time (Standard), Local Apparent Time, with Italic, Babylonian, Temporary hours, etc. Ah ha! I must have misunderstood the issue being discussed. I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. If the third class is already known by common usage as Bifilar, then I accept that it makes sense to call the second type Monofilar (even though for me personally the word filar carries an implication of a wire or thread, rather than being a general term for a line or edge). I assume the first class are called Nodal. The other half of the discussion is what to call a dial with a seasonal time adjustment. I though that someone was suggesting that because the existing examples had already been called monofilar then that name applied to the adjustment feature. So a monofilar dial can be Standard, Local , or other hours Upright, polar axial (axial?), or other principal axis Horizontal, Vertical or other dial face planes So the ordinary garden dial could be called Axial Local Horizontal Monofilar, Mr.Singleton's dial is Axial Standard Horizontal Monofilar. The various forms af azimuthal dials are all Upright monofilars. The Wenger dial is a Local Spherical Nodal dial. Am I getting close? Steve
Re: Azimuthal sundials - again
I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. You forgot (at least) one: - projection of many lines onto a point on a surface. (see NASS Compendium Vol.1 nr.3 page 6 or BSS bulletin 91.2 page 14) - Thibaud Taudin-Chabot 52°18'19.85 North 04°51'09.45 East home email: [EMAIL PROTECTED] (attachments max. 500kB; for larger attachments contact me first)
Re: Azimuthal sundials - again
That was a short article but an interesting concept of mapping the lines on a transparent medium and showing time where their shadow meets a point. A page or two later in that Compendium, Fred Sawyer showed how a stained glass window could apply the concept. I know Claude Hartman has done several designs that use light that way. I respect the creativity of the concept and designs. They are really neat! Thanks. Warren Thom T. M. Taudin-Chabot wrote: I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. You forgot (at least) one: - projection of many lines onto a point on a surface. (see NASS Compendium Vol.1 nr.3 page 6 or BSS bulletin 91.2 page 14) - Thibaud Taudin-Chabot 52°18'19.85 North 04°51'09.45 East home email: [EMAIL PROTECTED] (attachments max. 500kB; for larger attachments contact me first)
Azimuthal sundials - again
I try to answer to some of the last messages on the subject John Carmichael has written: And I give you think that we should stop using the term monofilar to describe Singleton dials? I don't know the Singleton Sundial and so I cannot answer -- Sara Schechner has written: I am very much against using monofilar in this way. It is confusing and unhelpful. It seems to me that monofilar should refer to a special case of string-gnomon. I think that the definition Monofilar causes the same confusion of Bifilar,definition used and accepted by all, from almost 80 years. I think that, in general, there is some confusion also on the Bifilar sundials -- To John Davis, Steve Lelievre, Warren Thom .Sara Schechner and others I have called (in an article on The Compendium September 1998) Monofilar those sundials in which the element that casts the shadow is a rectilinear element and the set of the date lines have a shape chosen by the designer (as he wants) As Fer de Vries has already written the element DOESN'T HAVE TO BE necessarily a thread, a string or a cable but it can be the edge of a plate or of a balcony or the ledge of a building, a pole, etc. Moreover the date lines must not have necessarily the shape of concentric circles (even if these are simple to be traced) Therefore the common sundials with a polar style are included, as very particular cases, in this group (category) of sundials The Monofilar and Bifilar sundials can be built with any kind of Time: Middle Time (Standard), Local Apparent Time, with Italic, Babylonian, Temporary hours, etc. On the name of this category of sundials I accept whatever suggestion. I had also thought to other name as Mono-style , Mono-line, With linear shadow, etc.: every name can give confusion and be erroneously interpreted. As Fer has already written also in the Bifilar Sundials the elements that cast the shadows don't have to be necessarily threads, strings or cables, despite the fact that word Bifilar literally means two threads . Moreover they don't even have to be straight lines . A fine example of a great Bifilar Sundial is in Barcelona - Spain near the beach. It can be seen in the beautiful book of Rafael Sun Gayá Relojes de Sol. In it the two threads are : 1) an vertical element (of Plexiglas or of glass), in the plane E-W, with the edge with the shape of a parabola and 2) the horizontal edge of a plate (of Plexiglas or of glass) in the vertical plane North-South . The fact that almost always the Bifilar Sundials are built in a horizontal plane with two horizontal perpendicular threads has, in my opinion, historical and practical reasons : the sundial designed by Michnik in 1922 had these characteristics and the calculation with this configuration is more simple. To overcome the obstacle we can now use programs to calculate Bifilar Sundials on a whatever plane and with threads placed in a whatever way. -- Altitude Sundials As I have written in a precedent message that, in my opinion, the azimuthal sundials must have a vertical style. I try now to explain my thought on Altitude sundials The position of the Sun in sky is determined when we know his 2 coordinates in a given system of coordinates of reference. The main systems of coordinates that are used and have been used are : 1) the equatorial coordinates: hour angle and declination 2) the azimuthal coordinates (or local): azimuth and altitude (height) 3) the Ptolemaic coordinates: meridian angle and hectemoros angle 4) the Ptolemaic coordinates: vertical angle and horarius angle In each of these systems the first coordinate (the first angle) is a dihedral angle between the planes that belong to a pencil of planes all passing for the same straight line (axis or fundamental direction of the system of coordinates) The axis are: 1) the polar axis, 2) the vertical of the place (Zenith - Nadir), 3) the direction East-West, 4) the direction North - South The plane perpendicular to the axis is said equatorial plane of the system. They are : 1) the plane of the Celestial Equator, 2) the horizontal plane, 3) the vertical plane North-South (meridian p.), 4) the vertical plane East-West (First Vertical p.) The second coordinate (the second angle) is measured from the axis of the system to the direction of the Sun Or, and it is the same thing, this angle is measured on the plane passing through the axis of the system and the Sun between the direction of the Sun and the equatorial plane of the system As I have already written, if we want that the shadow in a sundial can be calculated knowing only the first coordinate (angle) the style has to be a straight line parallel to the axis of the system. So in 1) if we want that the position of the shadow is known when we know only the hour angle, .the style has to be parallel to the polar axis; in 2) if we want to use only the azimuth (azimuthal
Re: Azimuthal sundials - again
Gianni wrote: The Monofilar and Bifilar sundials can be built with any kind of Time: Middle Time (Standard), Local Apparent Time, with Italic, Babylonian, Temporary hours, etc. Ah ha! I must have misunderstood the issue being discussed. I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. If the third class is already known by common usage as Bifilar, then I accept that it makes sense to call the second type Monofilar (even though for me personally the word filar carries an implication of a wire or thread, rather than being a general term for a line or edge). I assume the first class are called Nodal. The other half of the discussion is what to call a dial with a seasonal time adjustment. I though that someone was suggesting that because the existing examples had already been called monofilar then that name applied to the adjustment feature. So a monofilar dial can be Standard, Local , or other hours Upright, polar axial (axial?), or other principal axis Horizontal, Vertical or other dial face planes So the ordinary garden dial could be called Axial Local Horizontal Monofilar, Mr.Singleton's dial is Axial Standard Horizontal Monofilar. The various forms af azimuthal dials are all Upright monofilars. The Wenger dial is a Local Spherical Nodal dial. Am I getting close? Steve
RE: Azimuthal sundials - again
Should the (projection) dial types by axial, linear, and bi-linear? -Original Message- From: Steve Lelievre [mailto:[EMAIL PROTECTED] Sent: Monday, February 28, 2000 3:34 PM To: Sundial mailing list Subject: Re: Azimuthal sundials - again Gianni wrote: The Monofilar and Bifilar sundials can be built with any kind of Time: Middle Time (Standard), Local Apparent Time, with Italic, Babylonian, Temporary hours, etc. Ah ha! I must have misunderstood the issue being discussed. I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. If the third class is already known by common usage as Bifilar, then I accept that it makes sense to call the second type Monofilar (even though for me personally the word filar carries an implication of a wire or thread, rather than being a general term for a line or edge). I assume the first class are called Nodal. The other half of the discussion is what to call a dial with a seasonal time adjustment. I though that someone was suggesting that because the existing examples had already been called monofilar then that name applied to the adjustment feature. So a monofilar dial can be Standard, Local , or other hours Upright, polar axial (axial?), or other principal axis Horizontal, Vertical or other dial face planes So the ordinary garden dial could be called Axial Local Horizontal Monofilar, Mr.Singleton's dial is Axial Standard Horizontal Monofilar. The various forms af azimuthal dials are all Upright monofilars. The Wenger dial is a Local Spherical Nodal dial. Am I getting close? Steve
Re: Azimuthal sundials - again
I should point out that my dial reads time by a projection of a point onto a point (the first point being on a surface) and that it reads standard time. Dan Wenger Gianni wrote: The Monofilar and Bifilar sundials can be built with any kind of Time: Middle Time (Standard), Local Apparent Time, with Italic, Babylonian, Temporary hours, etc. Ah ha! I must have misunderstood the issue being discussed. I can see that in abstract terms that we have dials which are - projection of a point onto a surface (perhaps curved) - projection of a line (perhaps curved) onto a surface (perhaps curved) - projection of two lines (perhaps curved) onto a surface (perhaps curved) - other non-projection types, such as the wonderful CD-diffraction dial. If the third class is already known by common usage as Bifilar, then I accept that it makes sense to call the second type Monofilar (even though for me personally the word filar carries an implication of a wire or thread, rather than being a general term for a line or edge). I assume the first class are called Nodal. The other half of the discussion is what to call a dial with a seasonal time adjustment. I though that someone was suggesting that because the existing examples had already been called monofilar then that name applied to the adjustment feature. So a monofilar dial can be Standard, Local , or other hours Upright, polar axial (axial?), or other principal axis Horizontal, Vertical or other dial face planes So the ordinary garden dial could be called Axial Local Horizontal Monofilar, Mr.Singleton's dial is Axial Standard Horizontal Monofilar. The various forms af azimuthal dials are all Upright monofilars. The Wenger dial is a Local Spherical Nodal dial. Am I getting close? Steve Daniel Lee Wenger Santa Cruz, CA [EMAIL PROTECTED] http://wengersundial.com http://wengersundial.com/wengerfamily
Re: Azimuthal sundials - again
From: Daniel Lee Wenger [EMAIL PROTECTED] I should point out that my dial reads time by a projection of a point onto a point (the first point being on a surface) Oops, I knew that... and that it reads standard time. ...but I didn't know that. Apologies, Steve
