If the mirror is sufficiently small, the reflected spot will appear to be a circle, but it will actually be elliptic for low solar elevations. The hour and declination lines will indeed be mirror images of those on a hemispherium. BSS members who attended the meeting in Cirencester will recall Mark Lennox-Boyd's description and model of a sundial very much like this, with a mirror and a curved ceiling, that he was building in Italy. Does anyone know if it has been built yet?
Regards Chris Lusby Taylor 51.4N 1.3W. "fer j. de vries" wrote: > Hi John, > > I have no idea if the reflected sunspot will be a circle or not. > I should experiment with this to see what happens. > > In any case, assuming the mirror is in the center of the sphere, the > reflected beam is perpendicular to the ceiling and it is rather easy to test > this with a peace of cardboard. > > However, no sun to see this day. > > Fer. > > Fer J. de Vries > ferdv+AEA-iae.nl > http://www.iae.nl/users/ferdv/ > Eindhoven, Netherlands > lat. 51:30 N long. 5:30 E > > ----- Original Message ----- > From: +ACI-John Carmichael+ACI- +ADw-johncarmichael+AEA-mindspring.com+AD4- > To: +ACI-fer j. de vries+ACI- +ADw-ferdv+AEA-iae.nl+AD4- > Cc: +ACI-Sundial List+ACI- +ADw-sundial+AEA-rrz.uni-koeln.de+AD4- > Sent: Sunday, January 13, 2002 3:19 PM > Subject: Equatorial Ceilng Dial > > +AD4- Hi Fer +ACY- others: > +AD4- > +AD4- Let's say you have a spherical room, built like a planetarium, where the > +AD4- walls curve up into the ceiling and you locate your mirror in the > center. > +AD4- (Actually, the room would be a quarter sphere, like an orange segment, > with > +AD4- one flat side being the floor, and the other flat side the southern wall > +AD4- with the window with mirror). > +AD4- > +AD4- Would the sunspot be perfectly round all the time? Also, what would the > +AD4- hour and declination lines look like? (Like the lines on a > hemispherium?) > +AD4- Would this be called an +ACI-Equatorial Ceiling Sundial+ACI-? > +AD4- > +AD4- John > +AD4- > +AD4- John L. Carmichael Jr. > +AD4- Sundial Sculptures > +AD4- 925 E. Foothills Dr. > +AD4- Tucson Arizona 85718 > +AD4- USA > +AD4- > +AD4- Tel: 520-696-1709 > +AD4- Email: johncarmichael+AEA-mindspring.com > +AD4- Website: +ADw-http://www.sundialsculptures.com+AD4- > +AD4- ----- Original Message ----- > +AD4- From: +ACI-fer j. de vries+ACI- +ADw-ferdv+AEA-iae.nl+AD4- > +AD4- To: +ACI-sundial+ACI- +ADw-sundial+AEA-rrz.uni-koeln.de+AD4- > +AD4- Sent: Friday, January 11, 2002 7:19 AM > +AD4- Subject: Polar Ceing Dial > +AD4- > +AD4- > +AD4- +AD4- Diallists, > +AD4- +AD4- > +AD4- +AD4- In my message of 2002-01-09 about the limits of a polar dial on a > ceiling > +AD4- I > +AD4- +AD4- ended with: > +AD4- +AD4- > +AD4- +AD4- +ADw- Who has an inclined ceiling, higher at the south end? > +AD4- +AD4- +ADw- Won't that be better? > +AD4- +AD4- > +AD4- +AD4- I wanted to know this for sure and I started with a ceiling with > an > +AD4- +AD4- inclination of 160 degrees in stead of 180 degrees. > +AD4- +AD4- A difference of 20 degrees as is shown in the attached picture. > +AD4- +AD4- > +AD4- +AD4- The mirror now gets an inclination of 0.5 ( phi - 20 ). > +AD4- +AD4- For latitude 52 this is 16 degrees. > +AD4- +AD4- > +AD4- +AD4- The pattern on the now inclined ceiling also is a polar dial. > +AD4- +AD4- > +AD4- +AD4- I did not look for the extreme limits, but just gave it a chance. > +AD4- +AD4- > +AD4- +AD4- Following the same procedure the polar dial is cut off at about > 3.5 > hours > +AD4- +AD4- before and after noon and it is seen that the mirror is less > inside. > +AD4- +AD4- (distance CB ). > +AD4- +AD4- > +AD4- +AD4- At the left the pattern for a south facing dial though CM with > +AD4- (pin)gnomon > +AD4- +AD4- CB is drawn. > +AD4- +AD4- > +AD4- +AD4- The mirror is at distance CM from C and that is shown with the > line KL. > +AD4- +AD4- > +AD4- +AD4- At summer solstice the mirror will be in the shadow of the edge > of the > +AD4- +AD4- ceiling untill about 3.5 hours before noon and is shaded again > 3.5 hours > +AD4- +AD4- after noon. > +AD4- +AD4- > +AD4- +AD4- So this configuration will work 7 hours at summer solstice. > +AD4- +AD4- A great improvement compared with an horizontal ceiling. > +AD4- +AD4- > +AD4- +AD4- I only need to rebuild my house............. > +AD4- +AD4- > +AD4- +AD4- Best wishes, Fer. > +AD4- +AD4- > +AD4- +AD4- Fer J. de Vries > +AD4- +AD4- ferdv+AEA-iae.nl > +AD4- +AD4- http://www.iae.nl/users/ferdv/ > +AD4- +AD4- Eindhoven, Netherlands > +AD4- +AD4- lat. 51:30 N long. 5:30 E > +AD4- +AD4- > +AD4- +AD4- > +AD4- +AD4- > +AD4- +AD4- > +AD4- +AD4- > +AD4- +AD4- > +AD4- > +AD4-
