Re: Query about solstices

[John Schilke]

Thank you, and a merry Holiday round of Solstice and Christmas to you!  This
is essentially what I had thought, but being from Oregon, I have misgivings
about whether the sun would break through the rain.  We now are almost tied
with our record for consecutive rainy days -- some 29, I believe!

Again, the very best.  I hope we might see you in Tucson.

John Schilke

- Original Message -

> Thanks for the question.  You are the second person to ask in 2
> days how to determine the day of the solstice, given the slow change in
> the Sun's declination.  The answer is not complicated, just clever.

Re: Query about solstices

[John Schilke]

Yes, Fritz, my answers were along this line of thought.  Do look at Judy
Young's neat reply.
Thanks,
John
>
> Just imagining... I would say you could find out when
> it WAS, but it would be quite impossible the first try.
> When the shadow deviated to within about a week of
> when you guess it might occur, mark the line and
> then count the days until it returns, maybe say 16 or
> so.  Then it OCCURRED 8 days ago.  Now next year
> it will be 8 days after your mark.
>
> Let us know if there are other ways than this.

RE: Query about solstices

[Fritz Stumpges]

This topic got me wanting to get a piece of pipe and try it!
>From my new Sky software, which I'm just getting to know,
I found that solstice is at about 11:22 on the 21st.  I
then got the declinations on the day before and after at this
time.  But the sun changes only 14 seconds(arc)/day.  This means
that on the 20th it is -23deg26m14s and on the solstice it
is -23deg26m28s.  How does this compare with other sources
for accuracy?

Anyway, at this required resolution, it would take a "pipe"
or earthen hole, 307 feet long, assuming a "pinhole" or? which
could be resolved as 1/4 of an inch of movement (@307 ft!) This
is to measure the actual movement that day with respect to the day
before and day after.  Is this correct?  And if so, I doubt
they really could resolve this.  This is 130 times smaller than
the apparent diameter of the sun!?

What do you all think?  There goes the fun I was going to have
with this endeavor tomorrow.  I'll be there celebrating this
magical moment anyway, as I'm sure many of you will

Cheers,

Fritz 

-Original Message-
From: Frank Evans [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 19, 2001 11:46 AM
To: sundial@rrz.uni-koeln.de
Subject: Query about solstices


Greetings fellow dialists,

You don't have to have a clear sky on the actual day you are wishing to
mark sunrise or sunset. Martin Brennan in his book "The Stones of Time"
showed elegantly how the people at Newgrange in Ireland did it five
thousand years ago with the rising solsticial sun shining down a long
shaft into the immense earthwork onto auxiliary marks for adjacent days.

More recently there is a simple noon line in Durham Cathedral dated 1829
with extra marks for five and ten minutes after noon. This line was
simply a clock regulator, though.

Frank, 55N 1W
-- 
Frank Evans

RE: Query about solstices

[David Pratten]

Dear Fritz,

Using Find Annual Feature function (sdxFindAnnFeatx)of the The SUN API
www.sunlitdesign.com/products/thesunapi I get the follwing value for the
solstice this December:

December 21 19:21:30.7143 [UT] (which is +/- 10 seconds of the true
value)

Compare with   http://aa.usno.navy.mil/data/docs/EarthSeasons.html which
shows the value to the nearest minute.

Using the Declination function (sdxDecl) we find the declination for
this time on the 20th, 21st and 22nd:

20th -23:26:06.7694
21st -23:26:20.9605 SOLSTICE
22nd -23:26:06.8546

Which have the following differences from the Solstice

20th -0:00:14.1911
21st 0  SOLSTICE
22nd -0:00:14.1060


David
www.sunlitdesign.com

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Fritz Stumpges
Sent: Thursday, 20 December 2001 9:12 AM
To: 'Frank Evans'; sundial@rrz.uni-koeln.de
Subject: RE: Query about solstices


This topic got me wanting to get a piece of pipe and try it!
>From my new Sky software, which I'm just getting to know,
I found that solstice is at about 11:22 on the 21st.  I
then got the declinations on the day before and after at this time.  But
the sun changes only 14 seconds(arc)/day.  This means that on the 20th
it is -23deg26m14s and on the solstice it is -23deg26m28s.  How does
this compare with other sources for accuracy?

Anyway, at this required resolution, it would take a "pipe"
or earthen hole, 307 feet long, assuming a "pinhole" or? which could be
resolved as 1/4 of an inch of movement (@307 ft!) This is to measure the
actual movement that day with respect to the day before and day after.
Is this correct?  And if so, I doubt they really could resolve this.
This is 130 times smaller than the apparent diameter of the sun!?

What do you all think?  There goes the fun I was going to have with this
endeavor tomorrow.  I'll be there celebrating this magical moment
anyway, as I'm sure many of you will

Cheers,

Fritz 

-Original Message-
From: Frank Evans [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 19, 2001 11:46 AM
To: sundial@rrz.uni-koeln.de
Subject: Query about solstices


Greetings fellow dialists,

You don't have to have a clear sky on the actual day you are wishing to
mark sunrise or sunset. Martin Brennan in his book "The Stones of Time"
showed elegantly how the people at Newgrange in Ireland did it five
thousand years ago with the rising solsticial sun shining down a long
shaft into the immense earthwork onto auxiliary marks for adjacent days.

More recently there is a simple noon line in Durham Cathedral dated 1829
with extra marks for five and ten minutes after noon. This line was
simply a clock regulator, though.

Frank, 55N 1W
-- 
Frank Evans

RE: Query about solstices

[Andrew James]

Surely the whole business of finding the solstice is like a slower analogue
of finding noon by observing solar altitude?

Just around noon the altitude changes extremely slowly, and it is hardly
possible to judge the time of maximum altitude exactly.  Here, today, noon
is at 12:04:49 but even if we take 20 minutes before and after then the Sun
will only be 8 minutes of arc lower.  1/365 of a day is about 4 minutes, and
that interval either side of noon will see the Sun lower than its noon
altitude by roughly 8 * (4/20)^2 = 0.3 minutes.  I am neglecting change in
declination, which is insignificant so near the solstice. 

Hence the benefit of taking altitude sights at known times some significant
time either side of noon and calculating the instant of noon from those.
Even if the times are only known by a clock which may not be correct, the
result is noon as shown by that clock, which can thus be corrected.
Conversely, if the clock is trusted, the longitude can be found.  In
general, one would allow for the rate of declination change for the day and
its effect on the two readings.  

Similarly, by analogy, we see the advantage of taking declination readings
(by whatever means) on noted dates a few days either side of the solstice.


Andrew James

RE: Query about solstices

[Roger Bailey]

John's question is a good one. Accurate determination of the solstice would
have been difficult for ancient cultures due to the low rate of change of
the declination and sunrise azimuth. The techniques suggested will work but
they require repeated observations under difficult conditions. Clear skies
to the horizon are rare these days.

But they did it! With stone circles, tunnels, and observation monuments, our
forbearers fixed the day of the winter solstice. Determining  that the sun
had stopped its descent and had started to return with its life giving
light, heat and energy was a critical event in most cultures. It is
unfortunate that this has been lost in our modern cultures although solstice
festivals still exist.  How many realize that the lights, stars, trees,
greenery, etc are all cultural residues of solstice celebrations. . We have
gotten away from the real and significant event, start of the new solar year
and now focus on festivals that have co-opted the theme. The constants in
all these festivals are light, renewal, salvation, rebirth, whether it is
Christmas, New Years, Epiphany, Saturnalia, Sol Invictus, St Lucia,
Chanukah, Mother Earth etc. All celebrate the return of the sun.

The current dates for these festivals reflect the difficulty in accurately
determining the date and the calendar in vogue when the date was set.
Saturnalia was a 10 day festival, Chanukah 7 and Christmas 12. Let's enjoy
the whole solstice season and celebrate the return of the sun.

Happy Solstice

Roger Bailey
Walking Shadow Designs

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of John Schilke
Sent: December 18, 2001 3:26 PM
To: Sundial Mail List; Judy Young
Subject: Fw: Query about solstices




 Greetings!

 It occurred to me today that I probably do not fully understand something
that would be of interest to the List.  Granted the difficulty of
determining the equinox, using only a dial or a Stonehenge-like ring (mainly
because of the rapid change in solar declination), I thought about the
opposite problem.  How does one, using either of these tools only, determine
the time (i.e., epoch) of the solstice, since the declination of the sun
changes very little over several days -- only a couple of minutes of arc
daily.

I've pencilled out some intriguing possibilities, but they all depend on
19th and 20th century math and astronomy.  How did the ancients do it?

I'm probably looking right at the answer and shall feel quite silly when it
is shown to me, but I still will ask.  Thanks for the help.

John F. Schilke, MD
Oregon City, Oregon, USA
122W36, 45N21

Re: Query about solstices

[MMB]

Hi:

Roger wrote

> Determining  that the sun
> had stopped its descent and had started to return with its life giving
> light, heat and energy was a critical event in most cultures. It is
> unfortunate that this has been lost in our modern cultures although solstice
> festivals still exist.  How many realize that the lights, stars, trees,
> greenery, etc are all cultural residues of solstice celebrations. . We have
> gotten away from the real and significant event, start of the new solar year
> and now focus on festivals that have co-opted the theme. The constants in
> all these festivals are light, renewal, salvation, rebirth, whether it is
> Christmas, New Years, Epiphany, Saturnalia, Sol Invictus, St Lucia,
> Chanukah, Mother Earth etc. All celebrate the return of the sun.
> 
> The current dates for these festivals reflect the difficulty in accurately
> determining the date and the calendar in vogue when the date was set.
> Saturnalia was a 10 day festival, Chanukah 7 and Christmas 12. Let's enjoy
> the whole solstice season and celebrate the return of the sun.
> 
> Happy Solstice
> 
> Roger Bailey
> Walking Shadow Designs


Here is a site to help you remind others of the solstice. For me of
course it is the summer solstice I celebrate. One card in particular on
this site is good for both.



I am sure many of you could add more clever cards but here is a beginning.

Maria
Tasmania
below 40 degrees S