Hello Warren, Lets start again :
Latitude = 42 Inclination of dial = 90 Declination of dial = 64 Calculated: style height v = -19.01 substyle at b = -135.05 longitude correction ts = 71.93 Now we have to deal with a horizontal azimuthal sundial at low latitude : 19.01S, that is even between the tropics. This will give problems with the hourlines if the sun's declination is near or lower then -19.01 degrees. ( that is about half november untill end january ) During that period some hourlines will cross each other and you can't get a good reading of the time. To show this I calculated an example for lat. -19.01. This example is for local suntime, just to show the effect. ( Only one half of the dial is in the picture. Mirror this side to get the full dial ) So I think that your wall isn't very suitable for such an azimuthal dial, with a style perpendicular to the wall. In stead of using the azimuth of 19.01 degrees South use your own azimuth by making a dial with a vertical style parallel to your wall. As date lines you could use horizontal parallel lines. Remark : Spin.exe as distributed can't calculate dials between latitude 25N and 25S. These restrictions were made because of the shown problems. Happy dialling, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: Warren Thom <[EMAIL PROTECTED]> To: fer j. de vries <[EMAIL PROTECTED]> Cc: Sundial List <[email protected]> Sent: Wednesday, February 23, 2000 8:52 AM Subject: Re: R: azimuthal gnomon length problem > Hi Fer, > > Thank you for checking my question. My instincts have told me that a dial on a > vertical surface with a perpendicular style was possible, even if azimuthal > might not be the best name for it. > > You were correct - my numbers were wrong. I should have said the wall was 26 > degrees south of west or 64 degrees west of south. I checked this out with your > program and I get the height of style to be about -19 degrees. I have checked > the declination of the wall several times and I have gotten between 25 and 26 > degrees. I think 25 might have given a style (or latitude where horizontal) of > around -18 degrees. It was by observation of the wall that I found the error. > I can look for the North star "through" the wall, and I knew the angle was > around 15- 20 but never as much as 40 degrees to the surface. Also, about now > 4pm is not far from a normal to the surface - but the design you sent - the time > was about 1pm. Sorry for my error. > > I do have a 4 foot by 8 foot piece of nice "sign" board to make this dial. I > must wait for warm weather to paint because my work area is inside the unheated > garage. I look forward to the project. Thank you for the help. > > Sincerely - Warren Thom > > > "fer j. de vries" wrote: > > > I read : > > latitude 42N > > vertical dial, that is inclination 90 degrees > > declination of dial 26 degrees from South to West > > > > I calculate : > > The height of style ( for a usual dial ) than is : v = -41.91 degrees. > > This equals to a horizontal dial at latitude 41.91S. ( not 18 as you wrote ) > > Where is the error ????? > > These values may be calculated with Zonwvlak. > > Attachment converted: Macintosh HD:spin3.gif (TIFF/JVWR) (0000F32A)
