Dear Warren,
Many thanks for supplying Bill Gottesman's comments
which I very much take to heart.
Getting good sightings at sunrise and sunset in real
life is seriously challenging and even when you are
in luck, the shadows are weak and the effect of
refraction is at its greatest and you have to
Dear Geoff,
Yes, you are absolutely right. Silly me for not spotting
a trivial simplification! It is, indeed, much neater to
write:
cos(az)=sin(dec)/cos(lat)
This also readily shows that reversing the sign of the
declination results in 180 degrees being added to (or
subtracted from)
Dear All,
The BBC has been trailing their broadcast of the Christmas
Eve Carol Service from King's College here in Cambridge
with this introduction...
At 3 o'clock, just as the shadows begin to lengthen,...
My first thought was that shadows begin to lengthen immediately
after 12 noon but, on
Frank,
The west-declining vertical dial on the side of my house has a gnomon shadow
which shortens until about 1440hrs and then lengthens. A hasty (and
therefore unreliable) calculation suggests that a vertical dial declining
about 38 degs west of south in the latitude of Cambridge might
Thank you all for the answer(s) to this little problem and for the
bread-crumb trail to try to retrace the derivation.
My original question was sparked by wondering about the maximum deviation
from east-west at the solstice(s) so I could display my erudition and bore
people with comments
I have not been able to follow this thread in detail during the holiday
turmoil, but it seems appropriate to note that my program, The Electric
Astrolabe (astrolabes.org/electric.htm) is very good at showing this sort of
thing both visually and numerically. You can even find the differences
Dear Geoff,
Yes, I agree with your hasty calculation (having
taken far longer than you to do it!)...
A hasty ... calculation suggests that a vertical
dial declining about 38 degs west of south in the
latitude of Cambridge might experience its shortest
shadow around 1500hrs.
This was one of
Hi Jack, Frank and al,
Your question What is the path of the sun at sunrise or set? is a good one.
The answer given by Frank is simple and subtle. Actually it is a Smart
question, posed by W. M. Smart in his Textbook on Spherical Trigonometry.
Prof Smart leaves it as a question to be solved by
How about a single (composite) photo of the sun rising AND setting on the
Winter Solstice?
http://apod.nasa.gov/apod/ap071222.html
Bob
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Dear Jack,
I enjoyed your the motivation...
My original question was sparked by wondering about
the maximum deviation from east-west at the solstice(s)
so I could display my erudition and bore people with
comments like: The sun rises in the East and sets in
the West, right? Well, not
Another year and the sun is still shinning. Merry Christmas and a Happy New
Year to all.
Steve Irick
Yorktown Va USA---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Robert Terwilliger wrote:
How about a single (composite) photo of the sun rising AND setting on
the Winter Solstice?
http://apod.nasa.gov/apod/ap071222.html
Bob
Beautiful!! Be sure to click through to the photographer's pages.
Some great astronomical and travel photos.
The pages of
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