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-
