Re: Ring dial corrections between latitudes
Dear Fer, Yes, you are right. Sorry for the false information. I was only thinking in two dimensions, not three! As you say, it is possible but inconvenient. Gravity make a mess of everything! Regards, Mike Your statement about using a sundial at another place is correct for usual dials to read time and date lines because the type of lines are based on the same coodinate system "hourangle, declination". This won't work for e.g. Babylonian, Italian, antique hours, only for usual hours. But it won't work for a ring dial that hang by a cord. At the new place the used coordinate system "azimuth, altitude" is different. Or you should "hang" the dial at a line parallel to the vertical of the original spot. This is rather clumsy for a portable ringdial. Just replacing the suspension point won't work. It still hangs parallel to the vertical of the new place and not parallel to the vertical of the old spot.
Re: Ring dial corrections between latitudes
Mike, Your statement about using a sundial at another place is correct for usual dials to read time and date lines because the type of lines are based on the same coodinate system "hourangle, declination". This won't work for e.g. Babylonian, Italian, antique hours, only for usual hours. But it won't work for a ring dial that hang by a cord. At the new place the used coordinate system "azimuth, altitude" is different. Or you should "hang" the dial at a line parallel to the vertical of the original spot. This is rather clumsy for a portable ringdial. Just replacing the suspension point won't work. It still hangs parallel to the vertical of the new place and not parallel to the vertical of the old spot. Best wishes, Fer. Fer J. de Vries De Zonnewijzerkringmailto:[EMAIL PROTECTED]http://www.de-zonnewijzerkring.nl Eindhoven, Netherlandslat. 51:30 N long. 5:30 E - Original Message - From: Mike Cowham To: Helmut Sonderegger ; Thaddeus Weakley ; Sundial List Sent: Saturday, August 06, 2005 10:39 AM Subject: Re: Ring dial corrections between latitudes Dear Helmut, What you have written surprises me because any dial can be used at any latitude as long as it is in the same position relative to the Sun. Therefore a Ring Dial only needs to have its suspension point moved so that it thinks that it is at the same latitude that it was designed for. For example, you can use a Horizontal Dial made for, say, UK, and move it to New Zealand as long as it is still in the exact position as it was in England. It may now be inverted but will tell the correct time (UK time, of course) near sunrise and sunset during NZ summer months. Move it out into space and it will work perfectly all of the time (as long as it orbits in synchronisation with the Earth). Regards, Mike Cowham Cambridge, UK A ring dial (farmers ring) never works correct in different latitudes. It just cannot be constructed for different latitudes at the same time (except you put on its inner side 2 different scales for different latitudes).
Re: Ring dial corrections between latitudes
Dear Helmut, What you have written surprises me because any dial can be used at any latitude as long as it is in the same position relative to the Sun. Therefore a Ring Dial only needs to have its suspension point moved so that it thinks that it is at the same latitude that it was designed for. For example, you can use a Horizontal Dial made for, say, UK, and move it to New Zealand as long as it is still in the exact position as it was in England. It may now be inverted but will tell the correct time (UK time, of course) near sunrise and sunset during NZ summer months. Move it out into space and it will work perfectly all of the time (as long as it orbits in synchronisation with the Earth). Regards, Mike Cowham Cambridge, UK A ring dial (farmers ring) never works correct in different latitudes. It just cannot be constructed for different latitudes at the same time (except you put on its inner side 2 different scales for different latitudes).
Re: Ring dial corrections between latitudes
Thad, A ring dial (farmers ring) never works correct in different latitudes. It just cannot be constructed for different latitudes at the same time (except you put on its inner side 2 different scales for different latitudes). If ring dials are constructed in the correct way than they work exactly and do not show any errors. But of course there is the problem that you cannot read exactly the time displayed if the ring diameter and/or the ring width is to small. Helmut Sonnengasse 24, A-6800 Feldkirch47.25 N, 9.59 EHomepage: http://web.utanet.at/sondereh - Original Message - From: Thaddeus Weakley To: Sundial List Sent: Friday, August 05, 2005 10:24 AM Subject: Ring dial corrections between latitudes Dear Fellow Dialists: To ensure I am not duplicating something that has already been done, has anyone developed a formula for showing the error a ring dial (with a fixed gnomon say 40N) will read when in different latitudes? I am trying to express more detail than I have in bold below but I'm not sure such can be easily done, considering the variation in sun altitude throughout a day in different latitudes. Or have I already expressed the situation about as well as it can be described to a general audience? Also, what ring dial graphing programs are out there? I am just aware of SONNE. Thanks, Thad Weakley 42.2N 83.8W Ann Arbor, Michigan RING DIAL: The Ring Sundial is an instrument that gives you the current time by casting a bead of light rather than a shadow. Hang the sundial from the chain to have the maximum exposure to sunlight. Position the sundial to allow sunlight to shine through the hole on the outer ring. The bead of light that is cast on the inner ring indicates the hour and the season. Such dials are made for particular latitude. While these dials are readable in other latitudes, there will be error as easy calibration isnt available. In general in lower latitudes the dial will read fast in the a.m. and slow in the p.m. In higher latitudes the dial will read slow in the a.m. and fast in the p.m. Start your day with Yahoo! - make it your home page
RE: Ring dial corrections between latitudes
The Sundials program I wrote for PC and Mac draws ring dials: http://advanceassociates.com/Sundials/Lufkin-SUNDIALS-PC/ http://advanceassociates.com/Sundials/Lufkin-SUNDIALS-MAC/ Regards, Brad From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Thaddeus WeakleySent: Friday, August 05, 2005 4:25 AMTo: Sundial ListSubject: Ring dial corrections between latitudes Dear Fellow Dialists: To ensure I am not duplicating something that has already been done, has anyone developed a formula for showing the error a ring dial (with a fixed gnomon say 40N) will read when in different latitudes? I am trying to express more detail than I have in bold below but I'm not sure such can be easily done, considering the variation in sun altitude throughout a day in different latitudes. Or have I already expressed the situation about as well as it can be described to a general audience? Also, what ring dial graphing programs are out there? I am just aware of SONNE. Thanks, Thad Weakley 42.2N 83.8W Ann Arbor, Michigan RING DIAL: The Ring Sundial is an instrument that gives you the current time by casting a bead of light rather than a shadow. Hang the sundial from the chain to have the maximum exposure to sunlight. Position the sundial to allow sunlight to shine through the hole on the outer ring. The bead of light that is cast on the inner ring indicates the hour and the season. Such dials are made for particular latitude. While these dials are readable in other latitudes, there will be error as easy calibration isn’t available. In general in lower latitudes the dial will read fast in the a.m. and slow in the p.m. In higher latitudes the dial will read slow in the a.m. and fast in the p.m. Start your day with Yahoo! - make it your home page
