Fw: Do sundials settable to anywhere in the United Kingdom exist?

[Wolfgang R. Dick]

This is from the mailing list for historic instruments.

> Gesendet: Dienstag, 01. Februar 2022 um 10:07 Uhr
> Von: "William Overington" 
> An: r...@maillist.ox.ac.uk
> Betreff: [rete] Do sundials settable to anywhere in the United Kingdom exist?
>
> I am not an expert on scientific instruments, but I have been interested
> for many years.
>
> I have been thinking about sundial design and I have thought of a
> design.
>
> Is it original or has this been done before please?
>
> I live in rural Worcestershire and so I have realized that sundials such
> as are often seen offered for sale in garden centres will, quite apart
> from anything to do with the equation of time, be out by about 8 minutes
> in Worcestershire as Worcestershire is around one hundred miles west of
> Greenwich.
>
> So I wondered if sundials exist adjustable as to gnomon angle so as to
> be settable to latitude, and being constructed of a disc with the gnomon
> on it and a surrounding annulus settable relative to the disc to
> difference in longitude from Greenwich, the annulus having clock time
> information engraved upon it.
>
> In addition I am wondering if the clock time engraved on that annulus
> can be represented not by one circle with a mark for each hour but by a
> wide annular ring such that for each hour of clock time there is a
> curved line from inner edge to outer edge, with the annular ring having
> upon it twenty-five circles, two for the first of January, one on the
> inner edge of the  annular ring and one on the outer edge of the annular
> ring, and one for the first day of each of the other eleven months, and
> one for a day near the middle of each month. So the circles not quite
> evenly spaced as months do not all have the same number of days. This so
> as to include the equation of time in the design.
>
> Maybe an original design, maybe not. Could we discuss this please?
>
> William Overington
>
> Tuesday 1 February 2022
>
>
> Do not reply to this message UNLESS you want to reply to the whole list.
> -
> To unsubscribe, e-mail: rete-unsubscr...@maillist.ox.ac.uk
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Re: The German 2021 Sundial Conference - an Afterthought

[Wolfgang R. Dick]

A complete list of all sundials in Birkenau (with small pictures and maps - 
click on the pictures) is available at 
https://www.sonnenuhren-birkenau.de/sonnenuhren-in-birkenau/standorte.html .
 
Best regards,
Wolfgang Dick
 

Gesendet: Dienstag, 17. August 2021 um 12:53 Uhr
Von: "Dan-George Uza" 
An: "Sundial List" 
Betreff: The German 2021 Sundial Conference - an Afterthought

Dear all,
 
For those interested in current gnomonic events: I would like to mention that 
there has been a sundial conference near Mannheim in Germany between 5-8 August 
which I had the pleasure to attend and post some photos on my Facebook account. 
 
The presentations (in German language) covered many interesting topics, ranging 
from sundial history, sundial books, sundial funding programs, sundial quizzes 
to modern technology applied to sundial manufacturing. The circa 70 
participants also had fun visiting local gnomonic sights in and around Birkenau 
in the Odenwald - a small town which holds an international record for the 
highest sundial density (8 sundials/square km). All attendees received an 
anniversary medal and a jubilee album, gifts which will also be sent to partner 
sundial organizations.
 
It was quite a special reunion since this year the German sundial working group 
(Fachkreis Sonnenuhren) celebrates its 50th anniversary. The group is part of 
the German Society for Timekeeping, a larger organization dealing with various 
areas of horology. 
 
I would like to thank the organizers for this wonderful and stimulating 
conference! I am already looking forward to next year's meeting. 
 
PS: If you would like to know more about the local sundials, I highly recommend 
the new book "Sonnenuhren in Birkenau" ("Sundials in Birkenau"). It's also in 
English and French, available via 
i...@sonnenuhren-birkenau.de[mailto:i...@sonnenuhren-birkenau.de]
 
--

Dan-George Uza

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Restoration and dissemination of ancient sundials

[Wolfgang R. Dick]

This project may of some interest to members of the Sundial mailing list:

Restoration and dissemination of ancient sundials
https://www.researchgate.net/project/Restoration-and-dissemination-of-ancient-sundials

Project goal:

Sundials are the graphic evidence of complex astronomical events,
constantly occurring on the celestial sphere, at huge distances. To set
them, frequently, there was the convergence of various doctrines, from
mathematics to physics, geography, cartography, from geometry to art:
this multidisciplinary convergence is the evidence of a fervent cultural
climate arisen in Europe between the fifteenth and nineteenth centuries.
In this rich intellectual scenery, several sundials of great artistic
and scientific value were built in Italy, in particolar in Campania, but
they are not adequately appreciated due to the progressive loss of the
related millenary culture of timekeeping by the Sun, erased by the
advent of modern watches. Ruined by negligence but also by the inability
to carry out adequate restorations, Neapolitan sundials are a precious
cultural heritage to urgently be saved, providing actions for both
conservation and restoration, but also for the dissemination of their
ancient knowledge, that is likely to be disperse definitively, as well
as rapidly, in the coming decades.

So far, two publications (one of them with full text) have been added to this
project so far.

Kind regards,
Wolfgang
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Catalogue of sundials in Stuttgart museum

[Wolfgang R. Dick]

Dear colleagues,

The Wuerttemberg State Museum at Stuttgart holds a rather rich
collection of instruments, among them many portable sundials. A
scientific catalogue of the sundial collection, compiled by Juergen
Hamel and Irmgard Muesch, has appeared today as vol. 63 of "Acta
Historica Astronomiae":
https://www.univerlag-leipzig.de/catalog/bookstore/article/1857-Die_Sonnenuhren_des_Landesmuseums_Wuerttemberg_Stuttgart

The catalogue describes 118 objects by texts in German and by
photographs (one or more pictures in colour of each object). Among them
are also several rare and very interesting objects.

Some of the objects are also described in the digital catalogue of the
museum:
http://www.landesmuseum-stuttgart.de/sammlungen/digitaler-katalog/
(search for "Sonnenuhr"). However, the descriptions in the book are more
extended. The printed catalogue contains also registers of the types (17
main types + 6 sub-types), of the 55 makers, of other names mentioned in
the descriptions, and of the proveniences.

Best regards,
Wolfgang
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PS to Frederick Jaggi

[Wolfgang R. Dick]

PS: A compilation of the interesting messages sent by
Fredrick Jaggi to the Sundial Mailing List is available at
http://www.mail-archive.com/search?l=sundial@uni-koeln.de=from:%22Frederick+Jaggi%22
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Frederick Jaggi has passed away

[Wolfgang R. Dick]

Dear list members,

During this night I received these sad news from the family of
Fred Jaggi:

> Sent: Saturday, 08 April 2017 at 19:52
> From: "Frederick Jaggi" <f...@cox.net>
> To: "Wolfgang R. Dick" <wd...@astrohist.org>
> Subject: Re: Henry Spencer Spackman
>
> Dear Mr. Dick,
> 
> We are writing to inform you that a member of your email list, Frederick 
> Jaggi has passed away.  We are terribly sorry that you were not informed 
> earlier.  
> 
> If you would kindly remove him from any future emails, it would be greatly 
> appreciated.
> 
> Thank you,
> The family of Fred Jaggi

According to http://thebutterfieldhome.com/obituaries_view.php?id=403
Fred passed away on September 24th, 2016. The obituary states that he
was a member of the North American Sundial Society and that he "took
great joy in hand crafting complex scientific equipment including ...
sundials and orreries." See also
http://www.legacy.com/obituaries/name/frederick-jaggi-obituary?pid=100181644669=guestbook

Kind regards,
Wolfgang

Dear list administrator(*),

Please remove his address <f...@cox.net> (?) from the list.

(*) I do not know who it is currently.
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PS to Henry Spencer Sackman

[Wolfgang R. Dick]

PS: At the end of my previous message I made a typo. I intented
to write: "(Or to sell it more easily.)"
Somewhere the book under the wrong title was announced to be
helpful to construct sundials, which is a misleading information.
But a book on how to build sundials may sell better than a book
on their history.
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Henry Spencer Spackman

[Wolfgang R. Dick]

It seems to be nearly impossible to find information on
Henry Spencer Spackman, the author of The Timepiece of Shadows:
A History of the Sun Dial. New York : W.T. Comstock, 1895.
This book is available online at
https://catalog.hathitrust.org/Record/100773424 and
https://archive.org/details/cu31924031362142 .

The review and the annotation of the book in
Book News Vol. 13, July 1895, p. 457 and p. 480
(available online in Google Books, but outside the USA only
through a proxy server) do not say anything about the author.

There was a Reverend Henry Spencer Spackman (1811-1875) in
Philadelphia, but he ccould hardly be the author. The latest year
mentioned in the book is 1887, so even if we assume that the book
was edited and printed posthumously (e.g. by his wife, who was still
living in 1920), the year 1887 in the text makes this assumption
improbable.
About this reverend, see
http://www.legis.state.pa.us/cfdocs/legis/BiosHistory/MemBio.cfm?ID=5516=S

A better candidate would be the engineer and officer of the
same name, who also lived in Philadelphia and was still alive in
1920. But I could not find any proof that he was really the
author of the sundial history book.

Both persons were also called Henry S. Spackman.

Ernst Zinner (Alte Sonnenuhren an europäischen Gebäuden. 1964, p. 222)
cites the book as:
SPACKMAN, H. Spencer: The Timepiece of Shadows. A History of the sundial.
New York 1895

But this is the only case that the author was called "H. Spencer Spackman",
and there is no single trace of such a person. Zinner was not always
precise in his data.

Here is something about the engineer Henry Spencer Spackman:

Encyclopedia of Pennsylvania Biography, Vol. 13, 1921, p. 55-56
(not availabe online, the following texts are from Google snippet view):
"SPACKMAN, Henry Spencer,
World War Veteran.
Henry Spencer Spackman, lieutenant-colonel, Corps of Engineers, United
States Army, and a Chevalier of the Legion of Honor, has long been
numbered among the leading citizens of old Philadelphia.
Lieutenant-Colonel Spackman was president of the Henry S. Spackman
Engineer-Company, of international reputation, and is quietly but
potentially identified with the most essential interests of his home
city. Henry Spencer Spackman was ..."
"Lieutenant-Colonel Spackman was recognized as an authority on both the
manufacture and use of Portland Cement and contributed many articles to
the technical press. In politics Lieutenant-Colonel Spackman is a
Republican. He is a director of the Ardmore National Bank. The
organizations in which he is enrolled include the American Society of
Mechanical Engineers, the American Society of Testing ..."
(The Encyclopedia of Pennsylvania Biography is not available in
Germany, so if someone in the USA can have a look at this volume,
this may be helpful. Perhaps the sundial book is mentioned and
dates of birth [and death?] are given.)

American Legionnaires of France: A Directory of the Citizens of the
United States on Whom France Has Conferred Her National Order, the
Legion of Honor, 1920, p. 380:
"SPACKMAN, HENRY SPENCER. Engineer. Born in Williamsport, Pa.; educated
at Episcopal Academy, Philadelphia. President, Henry S. Spackman
Engineering Company, Philadelphia ..."

Who's who in the Construction Division of the United States Army, 1920:
"SPACKMAN, HENRY S., Lieutenant Colonel, Engineers; entered service and
commissioned Major, July 19, 1917; promoted to Lieutenant Colonel,
September 21, 1918. ..."
(The complete text is available through the World Biographical System
Online, free of charge for people living in Germany. I may send it
offlist on request, but it is of no help for the question whether he
was the author of the sundial book and does not give dates of birth
and death.)

The sundial book (or a second one?) was also announced as
"The Timepiece of Shadows; or, How to Build Sun Dials.
By Henry Spencer Spackman"
(e.g. in Country Life, Vol. 1, 1901, p. xxxii  and in
House & Garden, vol. 16, 1909, p. 185), but no library has such
a book, and it seems that the second part of the title was
given differently just by mistake. (Or to see it more easily.)

I could not not find any other person of the name Henry Spencer Spackman.

Regards,
Wolfgang
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Re: Spackman, Green, and Cole

[Wolfgang R. Dick]

It seems that I sent this twice to Karlheinz Schaldach, but not to the list.


Dear Karlheinz,

> T. W. Cole, who wrote Origin and use of Church Scratch Dials, London 1935,
> which is only one of his publications.

There are more publications by him. From different sources I compiled:

Cole, T. W. The Origin and use of Scratch-Dials (London, 1935),
reprinted 2001

Cole, T. W. Classification of church scratch-dials. 1935

COLE, T. W. Scratch-dials and medieval sun-dials.
History and relation to scientific sundials. (Stratford St. Andrew, 1938

Cole, T. W. Scratch dials or medieval sundials :
supplementary list to the list given in "Origin and use of church 
scratch-dials".
Stratford St. Andrew, Saxmundham : [Privately published 1945]

Cole, T. W. Church Sundials in Medieval England:
Reginald Taylor Prize Essay 1945. 1947
(Also cited as: Cole, T. W. Church sundials in medieval England.
Brit. Archaeol. Assoc. Jour. for 1945-7, 3rd ser. X (1948) 77-80.
[Reginald Taylor Prize Essay, 1945. Summarised by A. J. Hatley.])

Perhaps this publication in Brit. Archaeol. Assoc. Jour. contains
some biographical information, because it is related to a prize.


Two more findings:

David A. King, George Saliba: From deferent to equant: a volume of studies
in the history of science in the ancient and medieval Near East in honor
of E.S. Kennedy. 1987, p. 138:
"These wall dials, often called scratch dials, are described in Zinner,
1964, and in a series of three pamphlets published privately by T W. Cole ..."

Norfolk Archaeology, Or, Miscellaneous Tracts Relating to the Antiquities
of the County of Norfolk, Vol. 25, 1935, p. 452:
"Mr. T. W. Cole, of London, is making an effort to record and classify
the primitive sundials, or scratch dials, on churches: hitherto the
recognition of the subject seems to have been general rather than exact.
Mr. Cole has published an interim list, ..."

I could not find his first name(s).

Best regards,
Wolfgang
 
 

Gesendet: Donnerstag, 06. April 2017 um 08:36 Uhr
Von: "Karlheinz Schaldach" 
An: sundial@uni-koeln.de
Betreff: Spackman, Green, and Cole

Dear gnomonists,
I am seeking for informations on Henry Spencer Spackman, who rote The timepiece 
of shadows: a history of the sundial. New York 1895, on Arthur Robert Green, 
who wrote Sundials, Incised Dials or Mass-Clocks. New York / Toronto 1926, and 
on T. W. Cole, who wrote Origin and use of Church Scratch Dials, London 1935, 
which is only one of his publications.
1. What job had Spackman, when was he born, when did he die?
2. What job had Green, he was born 1865, but when did he die?
3. What do T. W. stand for? What was Coles work, when was he born, when did he 
die?
I would be glad if anyone of you could help,
Karlheinz--- 
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Arthur Robert Green (1865-1955)

[Wolfgang R. Dick]

Dear Karlheinz,

Here is some information on Arthur Robert Green (1865-1955), a surgeon:

see http://vidimus.org/issues/issue-71/feature/ :

""Mary had ... two brothers, Arthur Robert Green (1865-1955), and ..."

"Such an interest may have been encouraged by her older brother, Arthur,
who apart from practising as a surgeon, was an acknowledged authority on
medieval sun dials (also known as mass dials) and was eventually elected
a Fellow of the Society of Antiquaries on 16 January 1930.[10]"

"10. For a list of publications by Arthur Green, see Peter R.
Hamilton-Leggett ‘A Mass Dial Bibliography’, compiled in 1997
(http://www.ppowers.com/info/A%20MASS%20DIAL%20BIBLIOGRAPHY.pdf,
accessed July 2013)."

Best regards,
Wolfgang
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More publications by T. W. Cole

[Wolfgang R. Dick]

Here are some additions and two links to digitized publications
by T. W. Cole:

Sumner, John, Sir; Cole, T. W.: Worcestershire scratch dials.
Transactions of the Worcestershire Archaeological Society for 1932, v. 9, new 
series, 1933, pp. 21-24

Cole, T. W.: In Worcestershire Churches - Medieval Altar Slabs.
Transactions of the Worcestershire Archaeological Society, v. 10, new series, 
1933[1934?], p. 69

Cole, T. W.: Worcestershire Insised Crosses.
Transactions of the Worcestershire Archaeological Society, v. 15, new series, 
1938[1939?], p. 68

(see the index at http://worcestershirearchaeologicalsociety.org.uk/page13.html)

Cole, T. W. Scratch-dials on churches : interim list. Wimbledon : Hill Book 
Shop 1934, 10 pp.

Cole, T. W. The Origin and use of Scratch-Dials (Wimbledon: The Hill Bookshop, 
1935),
reprint: Herne Bay : Pierhead 2001,
online version of the original:
http://fulking.net/wp-content/uploads/2015/02/T_W_Cole_1935_Origin_and_Use_of_Church_Scratch_Dials.pdf

Cole, T.W.: Medieval Church Sundials.
AN HISTORICAL SKETCH REPRODUCED FROM "SCRATCH-DIALS AND MEDIEVAL CHURCH 
SUNDIAL",
Suffolk Institute of Archaeology & History, Vol. 23, 1938, Pt. 2, pp. 148-154
online version:
http://suffolkinstitute.pdfsrv.co.uk/customers/Suffolk%20Institute/2014/01/10/Volume%20XXIII%20Part%202%20(1938)_Mediaeval%20church%20sundials%20T%20W%20Cole_148%20to%20154.pdf

For even more of his publications, including newspaper articles, see:
Peter R Hamilton-Leggett: A mass dial bibliography,
http://www.ppowers.com/info/A%20MASS%20DIAL%20BIBLIOGRAPHY.pdf

Regards,
Wolfgang
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Aw: Spackman, Green, and Cole

[Wolfgang R. Dick]

Dear Karlheinz,

> T. W. Cole, who wrote Origin and use of Church Scratch Dials, London 1935,
> which is only one of his publications.

There are more publications by him. From different sources I compiled:

Cole, T. W. The Origin and use of Scratch-Dials (London, 1935),
reprinted 2001

Cole, T. W. Classification of church scratch-dials. 1935

COLE, T. W. Scratch-dials and medieval sun-dials.
History and relation to scientific sundials. (Stratford St. Andrew, 1938

Cole, T. W. Scratch dials or medieval sundials :
supplementary list to the list given in "Origin and use of church 
scratch-dials".
Stratford St. Andrew, Saxmundham : [Privately published 1945]

Cole, T. W. Church Sundials in Medieval England:
Reginald Taylor Prize Essay 1945. 1947
(Also cited as: Cole, T. W. Church sundials in medieval England. 
Brit. Archaeol. Assoc. Jour. for 1945-7, 3rd ser. X (1948) 77-80.
[Reginald Taylor Prize Essay, 1945. Summarised by A. J. Hatley.])

Perhaps this publication in Brit. Archaeol. Assoc. Jour. contains
some biographical information, because it is related to a prize.


Two more findings:

David A. King, George Saliba: From deferent to equant: a volume of studies
in the history of science in the ancient and medieval Near East in honor
of E.S. Kennedy. 1987, p. 138:
"These wall dials, often called scratch dials, are described in Zinner,
1964, and in a series of three pamphlets published privately by T W. Cole ..."

Norfolk Archaeology, Or, Miscellaneous Tracts Relating to the Antiquities
of the County of Norfolk, Vol. 25, 1935, p. 452:
"Mr. T. W. Cole, of London, is making an effort to record and classify
the primitive sundials, or scratch dials, on churches: hitherto the
recognition of the subject seems to have been general rather than exact.
Mr. Cole has published an interim list, ..."

I could not find his first name(s).

Best regards,
Wolfgang
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RE: No decision on future of leap seconds

[Wolfgang R. Dick]

Dear Rudolf and Roger,

The leap second comes from the fact that the Earth's rotation rate has decreased
since the definition of the second. Currently each day is 1 millisecond longer
than 24 hours in the mean. One has to regard the Earth as a clock, which is too
slow compared to a precise clock (= UTC running in parallel to atomic time TAI).
After one day the difference in time which the two clocks display is 1 ms,
after two days 2 ms, ..., after 1000 days 1 second. This is the leap second.
UTC clocks are stopped for one second, so that after this the two clocks
(Earth = UT1 and precise clock = UTC) are showing the same time again. 1000 days
is about 3 years - currently a leap second is introduced each 3 years in the
mean.

When the mean "length of day" (LoD, one day = 24 h + LoD)) was 2 ms in 1990s,
we had a leap second each 1 1/2 years in the mean (= 500 days). Since then the
Earth rotation has speeded up due to decadal fluctuations (core-mantle coupling
in Earth). But it will decrease again due to the Moon.

After the next 100 years, LoD will be about 3 ms in the mean. Then a leap second
will be needed every 333 days. And so on. This is a quadratic function with 
time,
i.e. the frequency of leap seconds increases quadratically with time. This will
be a big problem for our grandgrandgrand...children.

Best regards,
Wolfgang


Gesendet: Montag, 30. November 2015 um 12:18 Uhr
Von: "Roger W. Sinnott" 
An: sundial@uni-koeln.de
Betreff: RE: No decision on future of leap seconds

Rudolf,
 
If the day length starts at 86400 seconds and grows by 0.17 second each 
year, it would indeed reach 86401 seconds in about 6 years.  But if this 
rate is uniform, the tiny fractional increases would accumulate to 1 second in 
just 343 years, so I think that's when the first leap second would be needed.
 
  Roger
 

From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Rudolf 
Hooijenga
Sent: Monday, November 23, 2015 5:18 PM
To: 'Brooke Clarke'; sundial@uni-koeln.de
Subject: RE: No decision on future of leap seconds
 
. . . In fact, the Earth does slow down – and not just lately –, but this 
effect amounts to about 17 microseconds each year on average, and would only 
necessitate an extra leap second every sixty thousand years or so. The 
day-to-day fluctuations are much larger than this.
 
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No decision on future of leap seconds

[Wolfgang R. Dick]

ITU-R has decided not to decide anything now on the future of
leap seconds, but has postponed a decision to 2023 - see below.

By the way, am I right that all sundials would show wrong time
earlier or later if no leap seconds would have introduced?
(I mean at least the precise sundials which correct for the
equation of time and show time with a precision of minutes or even
better.)

A second question: What are the most precise sundials? In Furtwangen
I saw a large sundial with a claim to disply time to a second,
but I could not recognize this precision on the sundial itself.

And a third question: Are there already thoughts how to construct
a precise sundial in a world without leap seconds, when the zero
meridian for time will no longer be coincide with the geographic
zero meridian and will be shifted eastwards with time?

Best regards,
Wolfgang


Coordinated Universal Time (UTC) to retain "leap second"

New reference time scale to be considered by World Radiocommunication
Conference in 2023

Geneva, 19 November 2015 - The ITU World Radiocommunication Conference
(WRC-15), currently in session in Geneva from 2 to 27 November, has
decided that further studies are required on the impact and application
of a future reference time-scale, including the modification of
coordinated universal time (UTC) and suppressing the so-called "leap
second".

Leap seconds are added periodically to adjust to irregularities in the
earth’s rotation in relation to Coordinated Universal Time (UTC), the
current reference for measuring time, in order to remain close to mean
solar time (UT1). A leap second was added most recently on 30 June 2015
at 23:59:60 UTC. The proposal to suppress the leap second would have
made continuous reference time-scale available for all modern electronic
navigation and computerized systems to operate while eliminating the
need for specialized ad hoc time systems.

The decision by WRC-15 calls for further studies regarding current and
potential future reference time-scales, including their impact and
applications. A report will be considered by the World
Radiocommunication Conference in 2023. Until then, UTC shall continue to
be applied as described in Recommendation ITU-R TF.460-6
[https://www.itu.int/rec/R-REC-TF.460-6-200202-I/en] and as maintained
by the International Bureau of Weights and Measures (BIPM).

WRC-15 also calls for reinforcing the links between ITU and the
International Bureau of Weights and Measures (BIPM). ITU would continue
to be responsible for the dissemination of time signals via
radiocommunication and BIPM for establishing and maintaining the second
of the International System of Units (SI) and its dissemination through
the reference time scale.

Studies will be coordinated by ITU along with international
organizations such as the International Maritime Organization (IMO), the
International Civil Aviation Organization (ICAO), the General Conference
on Weights and Measures (CGPM), the International Committee for Weights
and Measures (CIPM), the International Bureau of Weights and Measures
(BIPM), the International Earth Rotation and Reference Systems Service
(IERS), the International Union of Geodesy and Geophysics (IUGG), the
International Union of Radio Science (URSI), the International
Organization for Standardization (ISO), the World Meteorological
Organization (WMO), and the International Astronomical Union (IAU).

"Modern society is increasingly dependent on accurate timekeeping," said
ITU Secretary-General Houlin Zhao. "ITU is responsible for disseminating
time signals by both wired communications and by different
radiocommunication services, both space and terrestrial, which are
critical for all areas of human activity."

"The worldwide coordination of time signals is critical for the
functioning and reliability of systems that depend on time," said
Francois Rancy, Director of the ITU Radiocommunication Bureau. "ITU will
continue to work with international organizations, industry and user
groups towards providing coherent advice on current and potential future
reference time-scales."

Source: ITU Press Release,
http://www.itu.int/net/pressoffice/press_releases/2015/53.aspx
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Re: Heinz Schumacher

[Wolfgang R. Dick]

Heinz Schumacher was a teacher at the vocational school for sculptors
and stonemasons (Friedrich-Weinbrenner-Gewerbeschule) in Freiburg im
Breisgau, in the south-west of Germany (close to the French Strasbourg),
and got the academic titles of Dipl.Ing. (Diplom-Ingenieur, i.e.
engineer with higher eduction) and of professor (Studienprofessor,
not university professor - sometimes teachers got this title also). For
25 years, until 1974, he had been the director of that school, and I
guess he retired in that year. Because he was born in 1909 (see below),
he was 65 in 1974, so that a retirement in that year is very probable.

This information is mainly from an article about the history of the
school:

http://www.natursteinonline.de/fileadmin/NatursteinDaten/Heftarchiv/2010/NS_10_1_aktuell/Im_Wandel_der_Zeit.pdf

It notes also that he teached his pupils about sundials.

There is a short note about him in the German journal Kosmos,
Vol. 71, 1975, p. 178, indicating that he was born on
7 September 1909 in Freiburg and that his fields of work
were Steintechnik, Bildhauerei, Sonnenuhren, which means
stonemasoning, sculpturing, and sundials.

https://www.deutsche-digitale-bibliothek.de/item/3BSQ7VGYIADNCKAO6RRFZQWIEP25RTC5
has an entry for Schumacher, Heinz Prof. Dipl. Ing.
from the collection of biographical newspaper cuttings in
the state archive (Landesarchiv) of Baden-Wuerttemberg,
indicating that he was born in 1909 in Freiburg and that he
was an architect.

However, other sources called him a sculptor and stonemason.

He also edited a booklet about the opening of the planetarium in
his (former) school in March 1975:
Das Freiburger Planetarium an der Gewerbeschule II,
Freiburg im Breisgau, Friedrichstrasse 51.
Festschrift zur Eroeffnung Maerz 1975. Red.: Heinz Schumacher.
Freiburg i. Br: Direktion d. Gewerbeschule II, 1975. 21 ungez. Bl.

I guess he is no longer alive, but I could not find from an
Internet search when he died.

Kind regards,
Wolfgang Dick
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Fw: Re: Heinz Schumacher

[Wolfgang R. Dick]

It seems that this information was sent only to me, but it may be of interest
also to others on the list.

By the way, the default reply option of the Sundial List is to send only to
the author of a message, not to the list. Only the Reply to all sends also
to the list (but this may depend on the mailing software). I am afraid that
several replies do not reach the list this way. I would propose to change
this reply default.

Kind regards,
Wolfgang


 Gesendet: Freitag, 26. September 2014 um 15:11 Uhr
 Von: Daniel Roth r...@infraroth.de
 An: wd...@astrohist.org
 Betreff: Re: Heinz Schumacher

 In addition: Heinz Schumacher died on June/13th 1998. From 1976 until 1985 he 
 was chairman of the Arbeitskreis Sonnenuhren within the Deutsche Gesellschaft 
 für Chronometrie e.V. From 1985 until 1998 he was honorary chairman of the 
 same unit.
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Two sundial resources on the Internet

[Wolfgang R. Dick]

Daniel Roth's sundial links at
http://www.infraroth.de/index.html?nav_d.html,/cgi-bin/slinks.pl
contain a link to
Almost 200 pictures of sundials  other astronomical clocks
(by Peter Lindner) at
http://home.arcor.de/peter.lindner/sundials.htm .

I visited this site today by chance when searching for something else,
and I found that the site now contains 959 Sundials/Astronomical clocks
in 3681 pictures as written in the header. Very worth a visit.

A more special source, but very comprehensive is the paper Historische
Sonnenuhren in der Erfurter Altstadt (Historical sundials in the
historic center of Erfurt, in German only) by Tim Erthel, published in
Mitteilungen des Vereins fuer die Geschichte und Altertumskunde
von Erfurt 72. Heft, Neue Folge, Heft 19, 2011, p. 41-71,
and available for complete preview at
http://books.google.de/books?id=k0YvN5iEqJMCpg=PA41 .

Best regards,
Wolfgang Dick
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Decision to eliminate the leap second deferred

[Wolfgang R. Dick]

Decision to eliminate the leap second deferred


The ITU Radiocommunication Assembly, held at Geneva, Switzerland, from
16 to 20 January 2012, decided to defer the development of a continuous
time standard in order to address the concerns of countries that use the
current system of the leap second in Coordinated Universal Time (UTC).

The decision has been reached to ensure that all the technical options
have been fully addressed in further studies related to the issue. These
studies will involve further discussions within the ITU membership and
with other organizations that have an interest in this matter and will
be referred to the next Radiocommunication Assembly and World
Radiocommunication Conference scheduled for 2015.

Adjustments made in one second steps, known as 'leap seconds', have been
implemented since 1972 to compensate for variations in the speed of the
earth’s rotation within the framework of UTC.

UTC is defined by ITU's Radiocommunication Sector and is maintained by
the International Bureau of Weights and Measures (BIPM) in cooperation
with the International Earth Rotation and Reference Systems Service
(IERS). Measurements from timing centres around the world are used in
the determination of UTC, which is adjusted to within 0.9 seconds of
Earth rotation time (UT1) by IERS-determined values of the Earth's
rotation. 

The suppression of the leap second would make continuous time scale
available for all the modern electronic navigation and computerized
systems to operate with and eliminate the need for specialized ad hoc
time systems. This however may have social and legal consequences when
the accumulated difference between UT1 - Earth rotation time - would
reach a perceivable level (2 to 3 minutes in 2100 and about 30 minutes
in 2700).

ITU Secretary-General Hamadoun Toure considered the decision taken by
the Radiocommunication Assembly will ensure that all stakeholders have
been adequately associated with a step which will clearly influence our
future.


Source: ITU Press Release,
http://www.itu.int/net/pressoffice/press_releases/2012/03.aspx
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Re: Decision to eliminate the leap second deferred

[Wolfgang R. Dick]

Dear Frank,

In principle, you are right. But firstly, this was not my report, but
a press release by ITU. And secondly, there are also arguments that
those who need solar time may use UT1. (In case that the leap second
will be abolished, IERS have plans to make UT1 more easily available.)

Today, a user wrote to the HASTRO-L discussion group:

Here in central Michigan our clock time is already adrift from true
local time by 40 minutes in the winter, and 100 minutes in the summer.
It will be a long time before we feel the lack of leap seconds to keep
it this way.

Discontinuing leap seconds will benefit those who study the historical
behavior of astronomical objects, since from the point that happens they
will no longer need to be taken into account.

Personally I am more or less neutral in this discussion. Both sides have
strong arguments. My only concern is that those who vote at ITU-R may
not understand the problems. It seems to me that ITU-R is not the right
organization to make this decision.

However, I will not discuss this further. There is a special discussion
group on leap seconds. And a lot of material is available at
http://www.ucolick.org/~sla/leapsecs/onlinebib.html .

Best regards,
Wolfgang
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Re: Future of UTC / leap second

[Wolfgang R. Dick]

Last Friday, a member of the History of Astronomy Discussion Group
(HASTRO-L) wrote the following concerning the possible redefinition
of UTC:

This is a curiosity.

It looks as if it might mean that mean solar time is no longer
tracked and made available.

The resulting situation might recall, in a way, what used to
happen in the nineteenth century, before time distribution became
well-established. Some municipalities far from other sources
would rely on friendly local observatories, some run by amateurs,
to provide them with clock corrections for mean solar time.  Some
of the observers left traces of their disagreements over the
details of how to do it, in popular astronomy periodicals of the time.

Here is my answer:

 It looks as if it might mean that mean solar time is no longer
 tracked and made available.

This is not true. UTC, used as civil time, is only an approximation to
mean solar time. It runs in parallel with TAI, the atomic time, thus
deviating more and more from mean solar time, unless a leap second is
introduced. UTC can be used instead of mean solar time only if you need
it with an accuracy not better than 0.5 sec or so. Otherwise you have to
use UT1, which is independent from UTC and its definition and which is
derived (and provided over the Internet) by the International Earth
Rotation and Reference Systems Service (IERS) in the form of tables, see
http://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html .
See also http://www.iers.org/IERS/EN/Service/Glossary/glossary.html for
explanations and links of some time-related terms.

In case that UTC will be redefined so that it cannot be used any longer
as an approximation to mean solar time, IERS intends to establish an UT1
service making UT1 more easily available over the Internet similarly to
current Internet UTC services. However, an approximation of the mean
solar time will then no longer be shown on our clocks and not be
transmitted with radio time signals.

Kind regards,
Wolfgang Dick
(This time officially as staff member of the
IERS Central Bureau)
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Future of UTC / leap second

[Wolfgang R. Dick]

Some time ago, there was a dicussion here on the future of UTC and
theleap second. Therefore I think that this announcement could
be of interest to some members.

BR, Wolfgang Dick



IERS Message No. 191   June 28, 2011



Colloquium on redefinition of UTC - Announcement


Decoupling Civil Timekeeping from Earth Rotation

A Colloquium Exploring Implications of Redefining UTC
in Astrodynamics, Astronomy, Geodesy, Navigation,
Remote Sensing and Related Fields

October 5-6, 2011

Headquarters of Analytical Graphics, Inc.
220 Valley Creek Blvd, Exton PA, 19341-2380
(near Philadelphia)

Registration is now open at http://futureofutc.org

Universal Time - the conventional measure of Earth rotation and
astronomical time-of-day - is the traditional basis for civil
timekeeping. Clocks worldwide are synchronized via Coordinated Universal
Time (UTC), an atomic time scale recommended by the Radiocommunications
Sector of the International Telecommunications Union (ITU-R).

A proposal to fundamentally redefine UTC will come to a conclusive vote
in January 2012 at the Radiocommunications Assembly of the ITU-R in
Geneva. It would halt the intercalary adjustments known as leap seconds
that maintain UTC as a form of Universal Time, and eliminate the
requirement that time services transmit the varying residuals (DUT1)
between Coordinated Universal Time and Universal Time of day. If the
proposal is approved, UTC would not keep pace with Earth rotation and
the value of DUT1 would become unconstrained.

Adverse impacts from redefining UTC have not been extensively researched
and documented. The implications extend from technical infrastructure to
legal, historical, logistical, sociological and economic domains.
Affected technologies may include (but are not limited to) applications
in astronomy, astrodynamics and celestial mechanics, geodesy,
ground-to-space satellite communications, navigation, remote sensing and
space surveillance.

This meeting will provide a venue for discussing and documenting the
repercussions of changing UTC along with possible mitigation strategies.

Co-chairs:
  Rob Seaman, National Optical Astronomy Observatory
  John Seago, Analytical Graphics, Inc.
  Steve Allen, University of California Observatories / Lick Observatory



IERS Messages are edited and distributed by the IERS Central Bureau.
To submit texts for distribution and to subscribe or unsubscribe,
please write to central_bur...@iers.org.
Archives: http://www.iers.org/Messages/


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Re: Kathleen Wright

[Wolfgang R. Dick]

Dear Frank,

The Oxford University Gazette vol. 129, 11 Mar 1999, No. 4505,
http://www.ox.ac.uk/gazette/1998-9/weekly/110399/coll.htm , gives:
OBITUARIES  ...
Lady Margaret Hall  ...
KATHLEEN WRIGHT (née Higgins), B.SC., MA, 1 January 1999;
scholar 1944--8. Aged 72.

This means that she was born in 1926. (Since she died on
1 January 1999 aged 72, she became 72 between 1 January 1998
and 31 December 1998 - thus she was born in 1926.)
Lady Margaret Hall of Oxford University should have a file
about her.

With Google Books I found that there is a short biography
of her (of Who's Who type) in Directory of British scientists
1964-65, which appeared in 1964
(see 
http://books.google.com/books?id=npZqMAAJq=%22Wright,+Kathleen%22+oxford):
WRIGHT, Kathleen (née Higgins) (retired), 
Unfortunately, the snippet view does not show more text.
As far as I know from other snippet views, this Directory does
not give birth dates or years.

Google Books also indicates an entry (without preview) in
Who's who of British scientists: Volume 1, 1963, but this must
be an error. The first edition of Who's who of British scientists
appeared in 1970, and there is no entry for Kathleen Wright in it
(I have this book in my library). Google Books contains many
errors in the bibliographic description. I guess it is the same
as above, the Directory of British scientists, but the previous
edition of 1963.

I would be interested in learning what is written about her in
the Directory of British scientists, and I would also be
interested in seeing the outcome of the work of her biographer.

Best regards,
Wolfgang

 Original-Nachricht 
Datum: Sat, 04 Dec 2010 20:53:02 +
Von: Frank King frank.k...@cl.cam.ac.uk
An: sundial@uni-koeln.de
Betreff: Kathleen Wright

Dear All,

A biographer has asked me whether I can supply
any details of someone he is writing about who
seems to have had some interest in sundials.

The bare facts are:

  Name:  Kathleen Wright (nee Higgins)

  Born:  Not known but about 1925

  Died:  1 January 1999

  Oxford University: 1944 to 1947

She wrote some reports on a couple of churches
where she particularly drew attention to their
scratch dials: Coln St Aldwyns and Bibury.

So far, the biographer has identified only one
person who was acquainted with Kathleen and he
said, unprompted, that she had a research interest
in old sundials.

I am pretty dismal at remembering names and do
not know whether this person is well known to
diallists (with better memories than mine) or
is quite unknown.

It should be easy to find out the date of birth
but I haven't managed even that :-(

It should be easy to find out her Oxford College
but this is proving challenging too.  There weren't
many women's colleges in those days so I may have
to search each one in turn.

If anyone has any leads please let me know.

Frank King
Cambridge, UK
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Re: Owls and sundials

[Wolfgang R. Dick]

I thought about another question: why was a humor journal named
The Sundial?. There is an association between light/sun and truth.
Real humor (or better to say satire) also tells the truth. Was a
sundial thought to be a device that tells the truth (= time)?

Best,
Wolfgang
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Re: SUNDIAL life before AND WITH clocks

[Wolfgang R. Dick]

Hi Sara,

These news about your forthcoming books sound fascinating!

By the way, JHA (vols. 1-39, 1970-2008) is available online at ADS,
http://adsabs.harvard.edu/journals_service.html when volume/page is
known, http://adsabs.harvard.edu/abstract_service.html for
author/title etc. searches.

Your article is at
http://articles.adsabs.harvard.edu/full/2001JHA32..189S

The following lengthy link yields a list of articles and reviews
with the title word sundials in JHA:

http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=ASTdb_key=PREqform=ASTarxiv_sel=astro-pharxiv_sel=cond-matarxiv_sel=csarxiv_sel=gr-qcarxiv_sel=hep-exarxiv_sel=hep-latarxiv_sel=hep-pharxiv_sel=hep-tharxiv_sel=matharxiv_sel=math-pharxiv_sel=nlinarxiv_sel=nucl-exarxiv_sel=nucl-tharxiv_sel=physicsarxiv_sel=quant-pharxiv_sel=q-biosim_query=YESned_query=YESadsobj_query=YESaut_logic=ORobj_logic=ORauthor=object=start_mon=start_year=end_mon=end_year=ttl_logic=ORtitle=sundialstxt_logic=ORtext=nr_to_return=200start_nr=1jou_pick=ALLref_stems=jha..data_and=ALLgroup_and=ALLstart_entry_day=start_entry_mon=start_entry_year=end_entry_day=end_entry_mon=end_entry_year=min_score=sort=SCOREdata_type=SHORTaut_syn=YESttl_syn=YEStxt_syn=YESaut_wt=1.0obj_wt=1.0ttl_wt=0.3txt_wt=3.0aut_wgt=YESobj_wgt=YESttl_wgt=YEStxt_wgt=YESttl_sco=YEStxt_sco=YESversion=1

I created this link by typing in sundials in the Title Words box
and jha.. as journal in the FILTERS section in the 
Select/deselect publications box. But I doubt that that this link
will come trough correctly with this email message.

Best,
Wolfgang


 Original-Nachricht 
Datum: Sat, 20 Nov 2010 09:59:34 -0500
Von: Schechner, Sara sche...@fas.harvard.edu
An: Sundial List sund...@rrz.uni-koeln.de
Betreff: SUNDIAL life before AND WITH clocks

I am addressing many of these questions in an interpretive catalogue of several 
hundred sundials and timefinding instruments at the Adler Planetarium and 
Astronomy Museum in Chicago (to be published in two volumes), and in a separate 
book, Sundials, Science, and Social Change (appearing later).


A summary of the main points can be found in this article:

The Material Culture of Astronomy in Daily Life:  Sundials, Science, and 
Social Change,  Journal for the History of Astronomy 32 (2001): 189-222.


I find that someone has scanned and posted it here:

http://www.antique-horology.org/_Editorial/schechner.pdf


Cheers,
Sara

Sara J. Schechner, Ph.D.
David P. Wheatland Curator of the Collection of Historical Scientific 
Instruments
Department of the History of Science, Harvard University
Science Center 251c, 1 Oxford Street, Cambridge, MA 02138
Tel: 617-496-9542   |   Fax: 617-496-5932   |   
sche...@fas.harvard.edumailto:sche...@fas.harvard.edu
http://www.fas.harvard.edu/~hsdept/chsi.html



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Owls and sundials

[Wolfgang R. Dick]

John,

There may be another connection - between humor and owls, since this was
a humor journal. In Germany the accociation between humor and owls
come from Till Eulenspiegel (Till Owlmirror, in English literature
known as Owlglass, see http://en.wikipedia.org/wiki/Till_Eulenspiegel).
Perhaps the former editor had this in mind, and because the journal
was called The Sundial, there was the connection between sundials and
owls. Just a guess.

Best,
Wolfgang

 Original-Nachricht 
Datum: Fri, 19 Nov 2010 08:43:02 -0700
Von: John Carmichael jlcarmich...@comcast.net
An: \'Sundial Mailing List\' sund...@rrz.uni-koeln.de
Betreff: FW: Sundial Information

Hi Dialists:

I received this intriguing letter from Ohio State University.  The writer
talks about an old publication called The Sundial.  And then asked me if I
am aware of any relationship between sundials and owls!  I am not aware of
any association between the two.  I asked him to send me any photos of this.
Meanwhile, I'm asking you guys if you have seen any relationship between
owls and sundials.

Thanks! 

I'll forward your answers to him, or you can write him directly.

John


From: Nathan Varrone [mailto:nathanvarr...@gmail.com] 
Sent: Friday, November 19, 2010 1:20 AM
To: jlcarmich...@comcast.net
Subject: Sundial Information


Dear John Carmichael,

I am currently reviving a humor magazine titled The Sundial at The Ohio
State University. In old issues of The Sundial, I often see an owl on top of
the drawn images of sundials. Is there any association with owls and
sundials that you would know of?

Thanks so much for your time, we may do business with you in the future!

Best,

-- 
Nathan L. Varrone 
The Ohio State University
Associate Director, 8th Floor Improv
President, The Sundial


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Fwd: Re: Cultural heritage of astronomical observatories

[Wolfgang R. Dick]

 Original-Nachricht 
Datum: Mon, 18 Oct 2010 09:22:35 +0200
Von: Giancarlo TRUFFA giancarlo.tru...@st.com
An: hastr...@listserv.wvu.edu
Betreff: Re: [HASTRO-L] Cultural heritage of astronomical observatories

Hello all.
The pdf file is here:

http://www.math.uni-hamburg.de/spag/ign/stw/Icomos09e.pdf

Regards
Giancarlo Truffa
Milan, Italy

-Original Message-
From: History of Astronomy Discussion Group [mailto:hastr...@listserv.wvu.edu] 
On Behalf Of Wolfgang R. Dick
Sent: Saturday, October 16, 2010 8:01 AM
To: hastr...@listserv.wvu.edu
Subject: [HASTRO-L] Cultural heritage of astronomical observatories

This may be of interest also to HASTRO-L users.

 Original-Nachricht 
Datum: Sat, 16 Oct 2010 07:56:19 +0200
Von: Wolfgang R. Dick wd...@astrohist.org
An: sund...@rrz.uni-koeln.de
Betreff: Re: Publication Cultural heritage of astronomical observatories

Unfortunately, this book is out of print. In June this year I ordered
it from the publisher (at a price of about 20 Euro), but I got the
answer that it is no longer available.

BR, Wolfgang

 Original-Nachricht 
Datum: Sat, 16 Oct 2010 15:41:30 +1100
Von: John Pickard john.pick...@bigpond.com
An: Sundial List sund...@rrz.uni-koeln.de
Betreff: Publication Cultural heritage of astronomical observatories

Good afternoon from a very chilly Sydney (where's Spring when you want it?),

The following book may be of interest to list members:

Wolfschmidt, G. (ed) 2009 Cultural heritage of astronomical observatories: From 
astronomical observatories to modern astrophysics (Proceedings of the 
International ICOMOS Symposium in Hamburg, October 14-17, 2008) Monuments and 
Sites series, No. XVIII. Berlin, ICOMOS-Hendrik Bäßler-Verlag, 2009. 378 pp. 
ISBN: 978-3-930388-53-0

You can order it from the ICOMOS Documentation Centre: 
http://www.international.icomos.org/icomos//publications/ms18.htm

However, despite some looking, I could not find a price mentioned anywhere, and 
it is not a free PDF.

The title page, and table of contents can be seen at 
http://www.math.uni-hamburg.de/spag/ign/stw/icomos221109-inhalt.pdf (5 MB)


Cheers, John

John Pickard
john.pick...@bigpond.com 
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Re: Sad news for the Sundial Community

[Wolfgang R. Dick]

Because I would like to include him into the second
edition of the Biographical Index of Astronomy (which includes
also sundial makers, see http://books.google.com/books?id=L8r5K_4bdxUC
for the first edition), I ask for his complete name.
The answer was: David L. Gard.

Best regards,
Wolfgang Dick

 Original-Nachricht 
Datum: Wed, 13 Oct 2010 19:47:16 -0700
Von: Roger Bailey rtbai...@telus.net
An: Bill Gottesman billgottes...@comcast.net, Sundial Mailing List 
sund...@rrz.uni-koeln.de
Betreff: Re: Sad news for the Sundial Community

Thanks for the note. Here is a link to the ATEN website with some pictures 
of his sundial.
http://atensundials.com/homepage.html  Clip and paste the url text into your 
browser.

Regards, Roger Bailey

--
From: Bill Gottesman billgottes...@comcast.net
Sent: Wednesday, October 13, 2010 6:47 PM
To: Sundial Mailing List sund...@rrz.uni-koeln.de
Subject: Sad news for the Sundial Community

  I learned from JD Gard's website for the ATEN sundials that David
 (Gard?), the inventor of the Aten heliochronometer, has died.

 I do not know if the company will still sell the sundial.

 I own one of the models, and it is a favorite to show guests.  It is
 readable to better than 1 minute.  I did not know Dave, but I certainly
 admired his originality and skill in manufacturing.

 It is worth noting that craftsfolk are mortal, and often their art
 disappears with them.  When I see a dial I like and can afford, I
 generally buy it sooner rather than later.  You never know when someone
 will stop making a dial, whether by choice or not.

 -Bill

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Re: Publication Cultural heritage of astronomical observatories

[Wolfgang R. Dick]

Unfortunately, this book is out of print. In June this year I ordered
it from the publisher (at a price of about 20 Euro), but I got the
answer that it is no longer available.

BR, Wolfgang

 Original-Nachricht 
Datum: Sat, 16 Oct 2010 15:41:30 +1100
Von: John Pickard john.pick...@bigpond.com
An: Sundial List sund...@rrz.uni-koeln.de
Betreff: Publication Cultural heritage of astronomical observatories

Good afternoon from a very chilly Sydney (where's Spring when you want it?),

The following book may be of interest to list members:

Wolfschmidt, G. (ed) 2009 Cultural heritage of astronomical observatories: From 
astronomical observatories to modern astrophysics (Proceedings of the 
International ICOMOS Symposium in Hamburg, October 14-17, 2008) Monuments and 
Sites series, No. XVIII. Berlin, ICOMOS-Hendrik Bäßler-Verlag, 2009. 378 pp. 
ISBN: 978-3-930388-53-0

You can order it from the ICOMOS Documentation Centre: 
http://www.international.icomos.org/icomos//publications/ms18.htm

However, despite some looking, I could not find a price mentioned anywhere, and 
it is not a free PDF.

The title page, and table of contents can be seen at 
http://www.math.uni-hamburg.de/spag/ign/stw/icomos221109-inhalt.pdf (5 MB)


Cheers, John

John Pickard
john.pick...@bigpond.com 
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RE: BSS web site

[Wolfgang R. Dick]

I have seen this type of advertisement already several times when a web site
is no longer active. It changes from page to page, e.g., when going to
http://www.sundialsoc.org.uk/Dial_Makers.htm ,
the ads are different (but somehow related to the original content).

When searching with Google for
site:www.sundialsoc.org.uk contacts
and clicking on Cached, one may extract the former contact addresses page
from Google's cache. Perhaps someone may contact one of the officers, e.g.:

Webmaster

Mr R C Mallett
21 Cantilupe Close
Eaton Bray
DUNSTABLE Beds.   LU6 2EA
Tel: 01525 15
Email: 100114@compuserve.com

General Secretary

Mr G Aldred
4 Sheardhall Avenue
Disley, STOCKPORT
Cheshire  SK12 2DE
Tel: 01663 762415
Email: gra...@sheardhall.co.uk

Kind regards,
Wolfgang Dick

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Re: The Pantheon

[Wolfgang R. Dick]

 Is the Roman Pantheon a colossal sundial?

A similar idea was already published in 2001 by Peter Mueller (Cologne,
Germany, a specialist for the architecture of historical observatories),
in his nicely illustrated and well-written book
Die Kuppeln von Rom.
Meisterwerke der Baukunst aus zwei Jahrtausenden.
Koeln, Weimar, Wien: Boehlau Verlag, 2001.
235 pp., 31 x 22 cm, ISBN 3-412-04001-0
(see pages 28-31, and see also my review of this book in
Beitraege zur Astronomiegeschichte Bd. 6, 2003, p. 227).
Mueller suggested that the Pantheon may have served as a calendar.

Best regards,
Wolfgang R. Dick
---
https://lists.uni-koeln.de/mailman/listinfo/sundial

Hugo Michnik

[Wolfgang R. Dick]

Here are a request from Rete and my reply. Does anyone know more about
Hugo Michnik? (Apologies for cross posting.)

--- Forwarded message follows ---
From:   Einstein [EMAIL PROTECTED]
To: rete [EMAIL PROTECTED]
Date sent:  Sat, 18 Nov 2006 09:23:28 +0100
Subject:[rete] Hugo Michnik

 Dears,
 
 Does anyone have any information about Hugo Michnik, a Polish astronomer that
 invent the bifilar sundial in 1932 and publish a paper in the magazine
 Astronomische Nachrichten?
 
 I'd be very pleasant to hear. Thanks.
 
 Joe Haverford

From:   Wolfgang R. Dick [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Date sent:  Sat, 18 Nov 2006 15:32:11 +0100
Subject:Re: [rete] Hugo Michnik

Hugo Michnik was a German high school teacher in Beuthen, Upper Silesia
(now Bytom, Poland - see http://en.wikipedia.org/wiki/Bytom_Odrza%C5%84ski
for a short information in English about the town, or follow the link
to the extended German Wikipedia page). He is mentioned in the following
web pages about sundials:

http://www.abelard.org/france/motorway-aires11_sundials.php :
Invented in 1922 by a German mathematician, Hugo Michnik, the two-wire sundial
is rather special.
http://www.de-zonnewijzerkring.nl/summaries/home-summaries-2003-3.htm : The
horizontal bifilar sundial with two crossing wires as a shade device was
invented in 1923, by Hugo Michnik of Germany.
http://members.aon.at/sundials/bild38_1e.htm : The inventor of the bifilar
sundial (two-thread clock) is professor Hugo Michnik, a high school mathematics
teacher in Beuthen, Upper Silesia, who issued a document regarding the 
'Therorie
einer Bifilar - Sonnenuhr' (Theory of a Bifilar Sundial) in 1922.
http://62.173.116.70/partnerpages/Lot.aspx?SaleHouseID=1040824SaleID=1109551UN
ID=210594062 : The system was first devised by Hugo Michnik, a teacher in the
Royal Gymnasium at Beuthen, Upper Silesia (now Bytom, Poland) in the first
decades of the century, publishing a full account of it in the Aztronomishe
Nachschriften 216 (1922) and 217 (1923).

The two papers in Astronomische Nachrichten of 1922 and 1923 are available
online at ADS (http://adsabs.harvard.edu/abstract_service.html).

Michnik published also:

Aufgaben aus der mathematischen Erd- und Himmelskunde ; I. Ueber die Laenge der
Tagbogen der Gestirne. II. Bestimmung der Kurve, die der hoechste Punkt der
Ekliptik ueber dem Horizonte eines gegebenen Beobachtungsortes beschreibt.
Beuthen: M. Immerwahr, 1905, 14 pp.

Beitraege zur Theorie der Sonnenuhren.
1. Untersuchung der temporaeren Stundenlinien antiker Sonnenuhren.
Leipzig : Teubner, 1914, 12 pp.
(Beilage zu dem Jahresberichte des Kgl. Gymnasiums zu Beuthen O./S. ; 1913/14)

The World Biographical Information System does not have an entry for him,
and I could not find a Dissertation (Ph.D. thesis, which usually contained
a biography). So it will hardly be possible to find more biographical
information, in case that no obituary was published.

Kind regards,
Wolfgang Dick

--- End of forwarded message ---
---
https://lists.uni-koeln.de/mailman/listinfo/sundial

Sundials in Vogtland, Germany

[Wolfgang R. Dick]

Dear sundialists,

The following message is asking for contact addresses concerning sundials in 
Vogtland (a region at the borders of Thuringia, Saxony and Bavaria in Germany). 
I will write it in German because it is intended for German specialists.

Best regards,
Wolfgang Dick

Liebe Sonnenuhrenfreunde in Deutschland,

mein Vater, der eine Homepage ueber Elsterberg im Vogtland und dessen weitere 
Umgebung (Greiz, Zeulenroda usw. in Thueringen, Reichenbach, Plauen usw. in 
Sachsen) betreibt, fotografiert seit einigen Monaten Sonnenuhren in dieser 
Gegend. Er hat bereits einige gefunden, die in dem Buch Sonnenuhren. 
Deutschland und Schweiz nicht vorkommen. Daher habe ich vorgeschlagen, dass er 
seine Ergebnisse auch den entsprechenden Arbeitsgruppen fuer Sonnenuhren in 
Thueringen und Sachsen bzw. der DGC mitteilt. Umgekehrt ist er an weiteren 
Informationen interessiert, denn sicherlich sind seit 1994 weitere Standorte 
bekannt geworden. Ist jemand in dieser Diskussionsgruppe, der sich fuer diese 
Region interessiert und der DGC zuarbeitet, oder der mir Kontaktadressen fuer 
Ost-Thueringen und West-Sachsen nennen kann?

Mit freundlichen Gruessen
Wolfgang Dick

-

Re: Save the Leap Second

[Wolfgang R. Dick]

  Keep the leap second, no leap hour.

The systems of time are rather complicated, and one cannot discuss it
with simple arguments without knowing all details. As a staff member
of the Central Bureau of the International Earth Rotation and Reference
Systems Service and member of the IAU working group on the future of
UTC, and also as historian of astronomy and person interested in sundials
I have thought much about this problem. I cannot explain all problems
in detail here, but I will try to mention some important points:

1. The introduction of the leap seconds at irregular and unpredictable
moments of time and the existence of a discontinous time scale bears
a lot of technical problems. That's why the GPS system does not use UTC
but introduced its own time scale, running in parallel to Atomic Time
TAI. There are very good arguments against leap seconds.

2. Our watches do not show UTC (except in Great Britain in winter).
And, as you know very well, they do not display true solar time.
Therefore, sundials only in very exceptional cases show the same time
as normal watches.
Our watches display zone time + (half of the year) 1 h. In summer
time, this may differ from local time by 1 1/2 h or more, in Russia
by 2 1/2 hour or more, and in China by several hours.
You have a leap hour twice each year when summer time starts or
ends, and you have a leap hour whenever you enter the next time
zone when travelling.
UTC is used in scientific and technical applications, not in
every-day life. The keep the time which is displayed by our watches
more or less connected to earth rotation, one can easily adopt
the zone time.

3. There is a time scale which is really following earth rotation:
UT1. This will be kept, and IERS will start a time service by
transmitting (details have to be fixed).
So, whenever you need a clock which displays time connected to
earth rotation (e.g., for pointing a telescope), you may use UT1.

To see some of the definition for leap second, UTC, TAI, UT1,
I may recommend the IERS Glossary at
http://www.iers.org/iers/earth/glossary/
and the links therein.

Best regards,
Wolfgang Dick
-

Re: Save the Leap Second (correction and addition)

[Wolfgang R. Dick]

The last sentence in point 2 of my previous message should have be:
To keep the time which is displayed by our watches
more or less connected to earth rotation, one can easily adopt
the zone time.

What I mean is the following: Today, Central European Time (CET) is
UTC + 1 h. When UTC differs from UT1 by nearly 1 second (usually
UT1 is behind UTC), UTC clocks are practically stopped for a second
(leap second). When there will be no leap seconds any longer,
after some 5000 years or so UTC will be ahead UT1 by about 1 h.
Instead of stopping UTC clocks for one hour (leap hour), one
may adopt zone time, so that CET = UTC. Great Britain will have
a zone time of UTC - 1 h, etc. We practice this twice each year
with summer time: Our watches have to be re-set by 1 h - but UTC runs
without any change! The same may be after 5000 years: UTC clocks
do not have to be re-setted, just our normal watches. Who cares about
UTC in every-day life? Our watches run in parallel to UTC
and normally do not display UTC. But the existence of a continues
time scale for technical and scientific purposes is very important.
There is no need to keep UTC connected to UT1.

When there will be no leap seconds, UTC is practically the same as
atomic time TAI, except for a shift. One could switch to TAI
as a continous time scale, but this would mean that the time scale
would be discontinous (the difference of UTC and TAI is 32 seconds
at this moment, next year it will be 33 seconds).

Wolfgang Dick

-

Re: Save the Leap Second

[Wolfgang R. Dick]

Dear Frank,

I well understand your arguments, but there are also very strong
arguments against leap seconds. So, one has to decide which
applications are more important: the many technical applications
which would go better without leap seconds, or applications like
sundials or traditional navigation which are the fields of
enthusiasts.

 Well all diallists and anyone who uses astronomical tables
 care about UTC precisely because it is, currently, guaranteed
 the same as UT1 to within 0.9s and we can ignore that difference.
 
 When UTC-UT1 is even a few seconds, never mind a large fraction
 of an hour, we won't be able to ignore the difference.

This is true. However, to get local time (true solar time), one
has to take into account much more than UTC-UT1. In the future,
one would just have to add one additional simple calculation.
UTC-UT1 will be more easily available in the future than it is
now, and if one needs it only with an error of about one second,
this can be predicted and tabulated in astronomical almanacs.
Just one additional simple table ... The difficulties with leap
seconds are much more complicated.

 I'll go further.  Everyone who ever sets a clock or a watch uses
 UTC or some very simple offset from UTC (usually an integral
 number of hours).  There are quite a lot of people who own watches!

True, but this is not the point. Why should UTC be close to UT1?
There is no reason besides the non-scientific astronomical applications
you mentioned. From a scientific/aesthetic point of view it would
be even better to use UT1 when one needs solar time instead of UTC
as an approximation.

 Moreover, most e-mail headers, certainly including yours, implicitly
 refer to UTC.  Your header said...
 
 Date: Tue, 12 Jul 2005 08:10:15 +0200 (MEST)
 
 That +0200 refers to the offset from UTC.

It will be the same without leap seconds. The only difference
will be that it will no longer be also the offset from UT1.
So, I should have asked: Who cares about UT1?

Best regards,
Wolfgang
-

(Fwd) RE: [rete] David Beringer

[Wolfgang R. Dick]

This is a reply from the Rete Discussion Group (History of
scientific instruments).

--- Forwarded message follows ---
From:   Gent van R.H. [EMAIL PROTECTED]
To: '[EMAIL PROTECTED]' [EMAIL PROTECTED]
Date sent:  Tue, 5 Jul 2005 09:58:32 +0200 
Subject:RE: [rete] David Beringer

Hi Wolfgang,

Hester Higton, _Sundials at Greenwich: A Catalogue of the Sundials, Horary
Quadrants and Nocturnals in the National Maritime Museum, Greenwich_
(Oxford, 2002), p. 438, lists

David Beringer (January 12, 1756 -- October 28, 1821)

and

Paul Beringer: Originally from Dieppe. He was working in Nuernberg c. 1736,
where he constructed many sundials. His sundials usually have two signatures -
his own and that of G.P. Seyfried, who worked with him.

===
* Robert H. van Gent  *
* E-mail: [EMAIL PROTECTED] *
* Homepage: http://www.phys.uu.nl/~vgent/homepage.htm *
===

--- End of forwarded message ---
-

Re: David Beringer

[Wolfgang R. Dick]

Beringer, David
* 1756 Nuremberg, Germany, + 28 October 1821 Nuremberg
see, e.g.:
Zinner, Ernst: Deutsche und niederlaendische astronomische Instrumente des
11. - 18. Jahrhunderts. 2. Aufl. Muenchen 1967 u. 1979, p. 247

Best regards,
Wolfgang Dick


On 4 Jul 2005 at 10:27, mainsa2 wrote:

 
 Friends,
 
 Do you know the village or town, and date of born and death of David 
Beringer, a
 dualist working cube dials in Nuremberg in the 17th or 18th centuries?
 
 Thanks for your help.
 
 Regards
 
 Thanks
 
 Rodrigo White

-

Re: David Beringer

[Wolfgang R. Dick]

Indeed, there seems to be David Beringer (1756-1821) who was born and died in 
Nuremberg, and a D. Beringer, who lived in Dieppe in 1725. However, it is not 
quiet clear who of these two made the 1736 and 1776 dials, and one should also 
check whether Zinner's data are correct.

The dates of birth and death which I sent before are from
Pilz, Kurt: 600 Jahre Astronomie in Nuernberg. Nuernberg 1977, p. 330.

David Beringer (1756-1821) is also mentioned as a globe maker in
Allmeyer-Beck, Peter E. (ed.): Modelle der Welt. Erd- und Himmelsgloben. Wien 
1997, p. 245.

The Websters Instrument Makers Database, 
http://www.adlerplanetarium.org/history/websters/
lists much more sources.

The date for BERINGER, D., AND G.P. SEYFRIED given there is
Germany, c. 1800, with the comment David Beringer.

It lists also a BERINGER, D. separately, with the comment
possibly David Beringer.

I hope this helps - but it seems that the (second?) D. Beringer needs to be 
investigated.

Are you on the Rete discussion group? If not, I may forward our
correspondence there - perhaps some specialists for scientific
instruments know more.

Best wishes,
Wolfgang

-

Re: sundials in the Frankfurt region

[Wolfgang R. Dick]

Sarah,

You should visit the Historisches Museum in Frankfurt, which have a good 
collection of sundials and other astronomical and scientific instruments. You 
may find the museum by searching the Internet with Google for Historisches 
Museum Frankfurt. There is also a catalog of their collection (which I do not 
have at hand, so that I cannot tell you now the exact title). However, it was 
made for a temporary exhibition, and only a smaller part of the items in the 
catalog are also in the permanent exhibition.

In case that you are interested also in historic geodetic instruments, I may 
arrange a visit to my institution (Federal Agency for Mapping and Geodesy) in 
Frankfurt.

Best regards,
Wolfgang Dick
(Potsdam/Frankfurt am Main)

-

Re: AW: Orthodox Easter (fwd)

[Wolfgang R. Dick]

Forwarded message:

 Date: Mon, 27 Apr 1998 18:03:07 -0500
 Reply-To: History of Astronomy Discussion Group [EMAIL PROTECTED]
 Sender: History of Astronomy Discussion Group [EMAIL PROTECTED]
 From: David J. Ross [EMAIL PROTECTED]
 Subject:  Re: AW: Orthodox Easter (fwd)
 To: [EMAIL PROTECTED]
 
 Professor Lourie in St. Petersberg responded with the following remarks to the
 cross post that I forwarded regarding the Easter computus, as it is known; it
 seems his remarks and references may still be of interest.
 
 Rev. Dave Ross
 
 
  From:
Basil Lourie [EMAIL PROTECTED]
  Reply-To:
Christianity in Late Antiquity Discussion Group
 [EMAIL PROTECTED]
 To:
Multiple recipients of list ELENCHUS [EMAIL PROTECTED]
 
 
 
 
 There are, in our days, three forms of the Christian Easter computus.
 
 Gregorian calendar is adopted not only by the Western Christians, but also
 by a diocese of the Patriarchate of Constantinople -- the Autonomous Church
 of Finland (since 1924 or perhaps 1926 -- sorry for this inexactitude).
 
 Julian calendar (completely or only as regard to the Easter computus) is
 retained by all other Oriental communities (not only Chalcedonian, but also
 others) with unique exception of the Church of Ethiopia.
 
 The Easter computus of the Ethiopian Church is even more archaic: it
 corresponds to the Alexandrian computus before the middle of IIIth century.
 On this see: O. Neugebauer, _Ethiopic Astronomy and Computus_ Wien 1979
 (Oesterreichische Akademie der Wiss., Philos.-hist. Kl., Sitzungsberichte,
 Bd. 347; Voroeffenlichungen der Komission fuer Geschichte der Mathematik,
 Naturwissenschaften und Medizin, H. 22).
 
 Also very useful are (I limite to the modern authors where the most part of 
 the
 references to the earlier literature are available):
 
 O. Neugebauer. _Abu Shaker's Chronography. A Treatise of the 13th Century
 on Chronological, Calendrical and Astronomical Matters, written by a Christian
 Arab, presented in Ethiopian_ Wien 1988 (Oesterreichische Akademie der Wiss.,
 Philos.-hist. Kl., Sitzungsberichte, Bd. 498).
 
 M. Richard. Le comput pascal par octa/et/eris, _Le Mus/eon_ 87 (1974); repr. 
 in
 Idem, _Opera minora_ I, Leuven 1976, # 21, p. 307-339.
 
 There are also some works on the particular systems, such as the history of 
 the
 Eastern computus in Georgian or in Armenian Churches or on the calendars of
 the Jewish world of the 2nd Temple period (based, first of all, on the 
 Qumranic
 data).
 
 Basil Lourie
 
 St.Petersburg Society for
 Byzantine and Slavic Studies
 
 [EMAIL PROTECTED]
 
 RUSSIA 194356
 St.Petersburg
 pr.Engelsa 135-132
 B.Lourie
 Fax 7(812) 559 
 
 
 
 
 Eugene F. Milone wrote:
 
  Yes, I agree that the problem of Easter is solvable in the Gregorian context
  alone; that's why I thought the Julian Calendar issue was a 'red herring'.
  Sources indicate that only the Slavonic churches are on the 'Old (i.e., 
  Julian)
  Calendar' at present.  I have no information about when the other Orthodox
  churches moved to the 'New Calendar'.  But the interesting thing is that
  all the Orthodox celebrate Easter on the same date -- unlike Christmas,
  which is rooted in the 13d difference between the Julian  Gregorian
  calendars.
  Cordially,
  - gene milone

Re: Orthodox Easter (fwd)

[Wolfgang R. Dick]

Dear sundialers,

Since the request concerning the date of Easter was also of interest for me,
I forwarded it to HASTRO-L and to a German specialist. The reply of the
latter I have distributed already in the previous message. Here follows
another reply together with the text of my request. I will also forward some
more replies. My apologies for the off-topic discussion, but it seems to me
of general interest.

Kind regards,
Wolfgang Dick


Forwarded message:

 Date: Wed, 22 Apr 1998 10:41:13 -0500
 Reply-To: History of Astronomy Discussion Group [EMAIL PROTECTED]
 Sender: History of Astronomy Discussion Group [EMAIL PROTECTED]
 From: Voula Saridakis [EMAIL PROTECTED]
 Subject:  Re: Orthodox Easter
 To: [EMAIL PROTECTED]
 
 Dear All:
 
 During the first centuries of Christianity there was no fixed date for the
 celebration of Easter.  In 325 AD the First Ecumenical Council among it's
 other decisions established the guidelines for calculating the date of
 Easter for all Christians.  The Council agreed that Easter should be
 celebrated on the first Sunday after the full moon for the spring equinox
 provided that the Jewish Passover had already been celebrated with the last
 provision being the most important.
 However these calculations were based on the Julian calendar which was
 scientifically incorrect.  After the Roman Catholic Church adopted the
 Gregorian calendar, it dropped the practice of celebrating Easter only after
 the Jewish Passover had taken place.  Since 1582 the Western Churches, Roman
 Catholic and Protestant Churches, have observed Easter irrespective to the
 date of Passover and hence, Eastern Orthodox Christians believe the Western
 churches are historically incorrect in their observance of this holiday.
 Hence the Eastern Orthodox Church is the only branch of Christianity that
 continues to celebrate Easter on the date that, to them, is historically
 correct according to the New Testament and the decrees of the First
 Ecumenical Council.
 
 Sincerely,
 
 Voula Saridakis
 
 
 The following request and reply comes from the Sundial Mailing List:
 
  [EMAIL PROTECTED] writes:
 
   ...  In my school we just has our Arab
   students out for very holy days,  our Greek Orthodox students observe
   Easter April 19, and my Unitarian friends  take spring break.
 
  I would have expected that the Orthodox churches define Easter in the
  same way as the Western churches, except that they use the Julian
  calendar.  It seems that would make the Orthodox Easter on average 13
  days later than the Western Eastern, but in any given year it would be
  either coincident or one month later.  How did it end up one week
  later this year?  Do they calculate the full moon differently as well?
 
  --Art Carlson--
 
 I am also interested in this question because I have relatives and friends in
 Russia and the Ukraine, and we wondered about the different dates of Easter.
 What I learned from a large encyclopedia is that together with the Gregorian
 calendar also a new rule for calculating the date of Easter was introduced.
 However, in both Julian and Gregorian calendars the full moon is calculated 
 not
 according to the real moon, but with respect to a fictitious moon. I guess 
 the
 difference comes from the way the moon is defined. However, I am not an 
 expert
 in this. So, does someone know how the date of Easter is calculated by the
 Orthodox churches?
 
 Wolfgang Dick, Germany
 
 *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*
 
 Voula Saridakis [EMAIL PROTECTED]
 Department of History   office: (540)231-8362
 428 Major Williams  fax: (540)231-8724
 OR
 Science and Technology Studies
 124 Lane Hall
 
 Virginia Polytechnic Institute and State University
 Blacksburg, VA  24061
 USA
 
 *^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*

Re: Orthodox Easter (fwd)

[Wolfgang R. Dick]

Forwarded message:

 Date: Wed, 22 Apr 1998 23:17:45 -0500
 Reply-To: History of Astronomy Discussion Group [EMAIL PROTECTED]
 From: David J. Ross [EMAIL PROTECTED]
 Subject:  Re: Orthodox Easter
 To: [EMAIL PROTECTED]
 
 Ok, one last comment, this address for a concise FAQ document, with links, on 
 the
 matter of the date's calculation and some history.  Hope I've not been a 
 pest
 
 DR
 
 www.landfield.com/faqs/astronomy/faq/part3/section-11.html

Again the test for those who do not have access:


When is Easter?

John Harper [EMAIL PROTECTED]


The popular rule (for Roman Catholics and most Protestant
denominations) is that Easter is on the first Sunday after the first
full moon after the March equinox.

The actual rule is similar, except that the astronomical equinox is
not used; the date is fixed at March 21.  And the astronomical full
moon is not used; an ecclesiastical new moon is determined by
adopted tables based on the Metonic cycle, and full is taken as the
14th day of that lunation.  There are auxiliary rules that make March
22 the earliest possible date for Easter and April 25 the latest.  The
intent of these rules is that the date will be incontrovertibly fixed
and determinable indefinitely in advance.  In addition it is
independent of longitude or time zones.

The popular rule works surprisingly well.  When the two rules give
different dates, that occurs in only part of the world because two dates
separated by the international date line are simultaneously in progress.

The Eastern Churches (most Orthodox and some others, e.g., Uniate
Churches in Palestine) use the same system, but based on the old
(Julian) calendar.  In that calendar, Easter Day is also between March
22 and April 25, but in the western (Gregorian) calendar those days
are at present April 3 and May 8. Whenever the Gregorian calendar
skips a leap year, those dates advance one day.

Some Eastern Churches find both movable feasts like Easter and fixed
ones like Christmas with the Julian calendar; some use the Julian for
movable and the Gregorian for fixed feasts; and the Finnish Orthodox
use the Gregorian for all purposes.

To explain the Eastern system one must begin with the Jews in
Alexandria at the time of the Christian Council of Nicaea in 325, who
appear to have been celebrating Passover on the first full moon
after March 21, as specified by the 19-year Metonic cycle and the
Julian calendar (with its leap year every 4 years, end of century or
not). The Bishop of Alexandria was made responsible for the Christian
calendar; he specified that Easter be the Sunday after that Passover.
Eastern Christians still say that Easter must follow Passover, but
that Passover is the one that is meant, not the Passover defined by
the present Jewish calendar.

Subsequently the Jews reformed their calendar (in 358 or in the early
6th century according to different sources; possibly at different
times in different places), in order to improve the fit between
astronomy and their arithmetic, but the Christians did not follow
suit.  In 1996, for example, Passover was on April 4 but the Orthodox
Easter was on Sunday April 14, not April 7 (which as it happens was
the Western Easter.)

The Eastern Easter is 0, 1, 4, or 5 weeks after the Western
Easter. The Western Easter can precede the (modern) Jewish Passover,
as in 1967, 1970, 1978, 1986, 1989 and 1997, and can even coincide
with it, as in 1981.

Much of this information was taken from the Explanatory Supplement to
the Astronomical Ephemeris, page 420, 1974 reprint of the 1961
edition.  There is more in the Explanatory Supplement, specifically a
series of tables that can be used to determine the Easter date for
both the Julian (Eastern and pre-1582 Western) and Gregorian
calendars.  However, the Explanatory Supplement is misleading on the
subject of the Eastern Easters, though its tables are correct.

Jean Meeus has published a program to compute Easter in Astronomical
Algorithms, also see below.  Simon Kershaw has written one in C,
available at URL:http://www.ely.anglican.org/cgi-bin/easter.

The most easily available published source for what the Jews 
and Christians were doing in ancient Alexandria appears to be Otto 
Neugebauer's Ethiopic Easter Computus in his _Astronomy and History 
Selected Essays_, Springer, New York, 1983, pp. 523--538. 

John Harper acknowledges the help of Archimandrite Kyril Jenner, Simon
Kershaw, and Dr. Brian Stewart concerning Eastern Easters.

Re: Easter Day

[Wolfgang R. Dick]

 [EMAIL PROTECTED] writes:
 
  ...  In my school we just has our Arab
  students out for very holy days,  our Greek Orthodox students observe
  Easter April 19, and my Unitarian friends  take spring break.
 
 I would have expected that the Orthodox churches define Easter in the
 same way as the Western churches, except that they use the Julian
 calendar.  It seems that would make the Orthodox Easter on average 13
 days later than the Western Eastern, but in any given year it would be
 either coincident or one month later.  How did it end up one week
 later this year?  Do they calculate the full moon differently as well?
 
 --Art Carlson--

Together with the Gregorian calendar also a new rule for calculating the date of
Easter was introduced. Please note that in both Julian and Gregorian calendars
the full moon is calculated not according to the real moon, but with respect to
a fictitious moon. I guess the difference comes from the way the moon is
defined. However, I am not an expert in this. I will try to find out with the
help of the HASTRO-L discussion group how the date of Easter is calculated by
the Orthodox churches.

Wolfgang Dick

Re: Size of sun and moon

[Wolfgang R. Dick]

Here is a reference which may contain something. I do not have easy access to
Vistas in Astronomy, therefore I canoot check it. The bibliographic data is
from ADS Astronomy Abstract Service (http://adsabs.harvard.edu/).

 Title:
Astronomy and the limits of vision
 Authors:
SCHAEFER, BRADLEY E.
 Affiliation:
AANASA. Goddard Space Flight Center, Greenbelt, MD, US
 Journal:
Vistas in Astronomy (ISSN 0083-6656), vol. 36, pt. 4,
p. 311-361
 Publication Date:
00/1993
 NASA/STI Keywords:
ATMOSPHERIC REFRACTION, NIGHT VISION, SEEING
(ASTRONOMY), VISIBILITY, VISUAL OBSERVATION,
COLOR VISION, DAYTIME, EXTINCTION, GLARE,
RESOLUTION, SHADOWS, SKY BRIGHTNESS, SOLAR
ECLIPSES, SUNSPOTS, TELESCOPES

 Abstract

Celestial visibility is the study of the limits of observability of objects in
the sky, with application to deducing the truth about historical events or to
the derivation of astronomical information of modern utility.  This study is
based on what is seen by ordinary humans, either in their everyday lives or at
times of historical events.  The results of such studies have more relevance to
non-scientists than does any other area of astronomy.  Celestial visibility is a
young discipline in the sense that the number of interesting applications with
simple solutions outnumber the solved problems; it is a broad interdisciplinary
field that involves work with astronomy, meteorology, optics, physics,
physiology, history, and archeology.  Each of these disciplines contribute
specialized mathematical formulations which quantify the many processes that
affect light as it leaves a source, traverses the atmosphere, and is detected by
the human eye.  These formulas can then be combined as appropriate to create
mathematical models for the visibility of the source under the conditions of
interest.  These model results can then be applied a wide variety of problems
arising in history, astronomy, archeology, meteorological optics, and
archeoastronomy.  This review also presents a dozen suggestions for observing
projects, many of which can be directly taken for individual study, for
classroom projects, or for professional research.

Re: Sundials in Lisbon(Portugal)

[Wolfgang R. Dick]

On Friday I sent the following reply to Bent Hirsberg. It may be of interest
for more members of the Sundial List, since it can be helpful for finding
answers to similar questions.

Wolfgang Dick

Forwarded message:

 From: Wolfgang R. Dick [EMAIL PROTECTED]
 Subject: Re: Sundials in Lisbon(Portugal)
 To: [EMAIL PROTECTED]
 Date: Fri, 09 Jan 1998 13:53:04 MET
 
 Here are a few results which I found with the help of Alta Vista
 (http://www.altavista.digital.com/) and the keywords
 +portugal +museum* +astro*
 
 Naval Museum, situated next to the Monastery of Jeronimos in Lisbon
 http://www.cncdp.pt/oceanos/n22/artigos/por/poring.html
 There is an extensive collection of craft, as well as naval artillery and
 nautical instruments (of particular note is the display of nautical astrolabes
 and planispheres - the largest collection of astrolabes in the world) showing
 important events in the history of the Portuguese navy, not only in the golden
 age of Portuguese navigation, but also in the centuries which followed.
 
 ST's Astronomical Directory: PORTUGAL
 http://www.skypub.com/astrodir/portugal.html
 
 Observatorio Astronomico de Lisboa (Astronomical Observatory of Lisbon)
 http://astro.cc.fc.ul.pt/OAL-eng.html
 (Most information in Portuguese only. There is a picture of a sundial in
 http://astro.cc.fc.ul.pt/edificioOAL.html)
 
 The last link is from my own page on historical observatories around the
 world: http://www.astro.uni-bonn.de/~pbrosche/hist_astr/ha_obs.html
 
 I have also a page on museums and other places related to astronomy
 (http://www.astro.uni-bonn.de/~pbrosche/hist_astr/ha_mus.html), but up to
 now there isn't anything from Portugal. I will add the above mentioned
 Naval Museum.
 
 You may find more when you will look on more links from the search with
 Alta Vista. You may also search for
 +portugal +sundial*
 (Or replace portugal by lisbon or lisboa. Upper case is not recommended,
 i.e., do not search for Lisbon.)
 
 Kind regards,
 Wolfgang R. Dick

Re: Book-Ordering

[Wolfgang R. Dick]

 where can I order (with some luck and via Internet) the book
 S.L.Gibbs 'Greek and Roman Sundials', New Haven and London 1976

Nor http://www.bookshop.co.uk/ (900,000 books), nor 
http://www.altbookstore.com/ 
(2 Million books) does have it in the data base. Most probably, it is indeed
out of print. But type in sundial and sundials in the search field. There
are some other interesting books, among them
Stones of Time : Calendars, Sundials and Stone Chambers of Ancient,
by Brennan, Martin, 1994.
(For links to these and other bookstores, publishers etc., see my pages
http://www.potsdam.ifag.de/server/biblio.html
http://www.astro.uni-bonn.de/~pbrosche/hist_astr/ha_pub.html
http://www.astro.uni-bonn.de/~pbrosche/hist_sci/hs_pub.html
They list also some antiquarians, which may be contacted in search for the book
needed.)

Wolfgang R. Dick
[EMAIL PROTECTED]

Greenwich Observatory Tercentennary dial

[Wolfgang R. Dick]

The page
http://www.ast.cam.ac.uk/pubinfo/leaflets/watertanks/watertanks.html
describes this sundial, but does not contain a picture.

Wolfgang R. Dick
[EMAIL PROTECTED]

Astronomiae Historia / History of Astronomy
http://www.astro.uni-bonn.de/~pbrosche/astoria.html

Change of URL for History of Astronomy WWW pages

[Wolfgang R. Dick]

On November 25th the port 8000 of the host server for the
Astronomiae Historia / History of Astronomy WWW pages has been replaced
by the standard port 80 (which need not to be specified). At the same time, the
server has been moved from machine aibn55 to aibn91. So, please change
your bookmarks or links from http://www.astro.uni-bonn.de:8000/... or
http://aibn55.astro.uni-bonn.de:8000/... to the new URL

http://www.astro.uni-bonn.de/~pbrosche/astoria.html

For those, who are not familiar with these pages:
Astronomiae Historia / History of Astronomy is the most comprehensive directory
of history of astronomy sources on the Web. E.g., currently there are links
to biographical material for 840 astronomers or other persons connected with
astronomy. Other themes are: Observatories and other places, Items
(Anniversaries, Archaeoastronomy, Astrology, Astrophysics, Calendars, etc.),
Archives and libraries, Museums, Research institutes, Publications,
Meetings, Societies, Historians of astronomy. There are also numerous links to
general resources in history and history of science.

Sundial links may be found at the page
History of Astronomy: Items: Instruments
(http://www.astro.uni-bonn.de/~pbrosche/hist_astr/ha_items_instrum.html).

Kind regards,
Wolfgang R. Dick

--
Please note that my phone number has changed!
Bitte beachten Sie meine geaenderte Telefonnummer!

==
Institute for Applied GeodesyNameDr. Wolfgang R. Dick
  ___  ___  Address Institut f. Angewandte
 / /   / ___/   /   | / _/ Geodaesie, Aussenstelle
/ /   / /__/ /| |/ / ___  Potsdam,  PF 60 08 08,
   / /   / ___/   / /_| |   / / /_ / D-14408 Potsdam, Germany
  / /   / /  / ___  |  / /__/ / Phone   +49 331 316-618
 /_/   /_/  /_/   |_| /__/ Telefax +49 331 316-602
  E-Mail  [EMAIL PROTECTED]
Geodetic Research DivisonURL http://www.potsdam.ifag.de/
==

Sundial information in the World Wide Web

[Wolfgang R. Dick]

Sundial information in the World Wide Web (WWW)
---

A lot of information about sundials is already available in the WWW. A starting
point for this may be
http://aibn55.astro.uni-bonn.de:8000/~pbrosche/hist_astr/ha_items_instrum.html ,
a document among the History of Astronomy WWW pages
http://aibn55.astro.uni-bonn.de:8000/~pbrosche/astoria.html .

Additions to this document are very appreciated but should be limited to
historical sundials.

Wolfgang R. Dick
Secretary of the Working Group for the History of Astronomy
in the Astronomische Gesellschaft
[EMAIL PROTECTED]


Appendix: The World Wide Web


The World Wide Web (WWW) is the universe of network-accessible information, an
embodiment of human knowledge. It is an initiative started at CERN, now with
many participants, and is growing exponentially.

The WWW has a body of software, and a set of protocols and conventions. It uses
hypertext and multimedia techniques to make the web easy for anyone to roam,
browse, and contribute to.

Each highlighted phrase (in color or underlined) is a hyperlink to another
document or information resource somewhere on the Internet.

The access to the WWW is available for everyone at prices comparable to that of
a telephone connection. To learn how to get access one may just go to the next
bookshop and buy one of the numerous books available.