Hello Fernando The shortest answer would be to have the cylinder with the dial on its outside and few styles around it so that at least one is working. The cylinder should be inclined so that is is parallel to the Earth axis. Then you would have longest expositions. On the poles it would work half a year continuously, on the Equator half a day.
For flat dials the answer is not so straightforward. If you recall equations they are combinations of trig functions and it is tricky to predict the results for different arguments. The best would be to experiment on the spots of interest :-) or use Fer's program which allows for fast calculations of dials for any latitude, orientation and inclination. For each lat you could perform few experiments for inclinations ranging from 0 (horizontal dial) to 90 (vertical) and see how the length of the exposure changes. If you made systematic research you could publish it because that would be of interest. All best Slawek At 07:54 AM 8/11/99 -0300, you wrote: >I sent this message yesterday but it was returned. >I thought the world could be over for you guys >who tried to see the eclipse. Since it seems it didn't, >here it is again: > > >Given a certain latitude, how can we find the "best" angles for >a sundial? > >For "best" I mean those that offer: > >a) the longest insolation during the day >b) the longest insolation at the various seasons >c) the best azimuth (declination) and the best reclination so the dial > can be place as high as possible and still get to be > seen confortably (based on the angle, not on the size). > >My guess is that if we are beyond 23 1/2 N or S, than >the sundial should be vertical and face South (N) or >North (S). This would give the "best" possible >angles which would allow the sundial to show every hour >from sunrise to sunset every day of the year. > >Now, if it sits in-between 0 and 23 1/2, is there are >"better" angle? > >For instance, Brasilia is 19d 45' 5" S (47 d 49' 59" W). >Of course, it the sundial is vertical and faces North, in December it >will >be useless. Now, the more I recline it, the longer it will work >towards the solstice in December. If I go as far as to have >horizontal, of course it will work all year round but will >not be seen if it is placed on the top of a column. > >If fact, I would guess I would never have to go beyond >23 1/2 degrees of reclination. > >Is this message to confusing? I think it is :-) >I am not sure I have been able to describe what I intended to >get: to place a sundial in the top of a 6-meter tall (19' 8") column >so as it can be the best possible visibility from the ground. >At the same time it should work all year round for a certain >latitude (in this case, 15 d 45' 5"S), from sunrise to sunset. > >Again, it seems clear it should face North. For visibility >from the ground, the the lesser the declination, the better. >For insolation... > >I hope this is less confusing now. > >- fernando > > > > >- fernando > > > >-- >Fernando Cabral Padrao iX Sistemas Abertos >mailto:[EMAIL PROTECTED] http://www.pix.com.br >Fone Direto: +55 61 329-0206 mailto:[EMAIL PROTECTED] >PABX: +55 61 329-0206 Fax: +55 61 326-3082 >15º 45' 04.9" S 47º 49' 58.6" W >19º 37' 57.0" S 45º 17' 13.6" W > > > Slawek Grzechnik 32 57.4'N 117 08.8'W http://home.san.rr.com/slawek
