Re: Perpetual Calendar of Giovanni Antonio Amedeo Plana

[Michael Ossipoff]

It's an amazing device, especially for its time, & its
mechanical-construction. I'd never heard of it till today.

When you google "Giovanni Antonio Amedeo Plana, perpetual calendar, Turin",
select the google link that says: "

The mechanism of Plana's Calendar - IMEKO

That looks like more than a magazine-article, & looks to have a more
detailed description of the device.

Michael Ossipoff



On Sat, Sep 24, 2022 at 1:22 PM graham stapleton via sundial <
sundial@uni-koeln.de> wrote:

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> -- Forwarded message --
> From: graham stapleton 
> To: "sundial@uni-koeln.de" 
> Cc:
> Bcc:
> Date: Sat, 24 Sep 2022 17:22:31 + (UTC)
> Subject: Perpetual Calendar of Giovanni Antonio Amedeo Plana
> While calendars are a current topic, please can anyone direct me to
> detailed information about the Perpetual Calendar created by Giovanni
> Antonio Amedeo Plana, located in Turin.
>
> I have discovered a paper: IMEKO-TC4-ARCHAEO-2017-008.pdf
> 
>  but
> it has few details. Apparently the University of Turin team built both a
> physical replica and a digital version, I have not found any references to
> these.
>
> Graham Stapleton
> ---
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>
>
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Re: Republican Calendar, Year 231

[Michael Ossipoff]

Though Steve objected to something that I said in an earlier post, my own
reaction to what I said was much worse than anyone else’s criticism could
be.

.

At first I didn’t understand why I didn’t like what I’d said.  But though I
meant no implied criticism of a country or its overall population, it could
easily have sounded as if such was implied.

.

The unfortunate words “over there” made it a national statement.  …& that
gave it a nationalist, political implication.  …completely unintended, but
nonetheless definitely there.

.

I’m not political, & want no part of politics or the trouble that
accompanies it, national or international.

.

Because I respect myself too much to want to say something like that, I
strongly didn’t like what I’d said.

.

Though there are other yearstart rules that are typically about 3 time more
accurate, the Gregorian leapyear is more than sufficiently accurate, as the
following will show:

.

Maximum Periodic Displacement  (mpd):

.

All calendars are periodically-displaced by oscillation about a middle
point.

.

The Gregorian leapyear rule results in an mpd of 1.5 days. That’s entirely
insignificant on the seasonal-scale.

.

…& I emphasize that that 1.5 days is the **maximum** extreme that the
periodic-displacement will reach over the entire 400-year Gregorian cycle.

.

Unidirectional Drift:

.

That middle about which the periodic displacement oscillates is, itself,
moving unidirectionally in yearstart rules that don’t use an actual
astronomical observation, but which, rather, use an arithmetical
approximation to the desired year-length.

.

But that drift-rate can be so small as to be unproblematic over many
centuries, or even, with some rules, millennia.

.

The Gregorian leapyear rule results, currently, in a drift-rate that is now
only 43 minutes per century.

.

>From 1582 to 1982 was exactly one 400-year Gregorian cycle. So the
periodic-displacement was zero.  But there was unidirectional drift,
because the Gregorian leapyear rule is based on an approximation to the
length of a Vernal-Equinox tropical-year.

.

That drift, from 1582 to 1982, was less than 3 hours, in terms of the
mean-tropical-year.  Not a week, not a day, but less than 3 hours.…
i.e., on the average throughout the year, any particular Solar ecliptic
longitude occurred at a calendar date-&-time less than 3 hours earlier than
it did in 1582.

.

In fact it was even less still, because the drift-rate was lower in earlier
centuries.  That’s because the drift rate is accelerating.   …because the
day-length is increasing,  resulting in fewer days in any
tropical-year.   …thereby
increasing the amount by which the Gregorian mean-year of 365.2425 is
longer than any one of the various tropical-years, including the mean
tropical-year.

.

So, incidentally, the drift-rate is different for the various
tropical-years (… e.g. reckoned at Vernal Equinox vs at Summer Solstice,
etc.)

.

Summary: The Gregorian leapyear rule has only negligible mpd &
unidirectional drift-rate.

.

I should add that I spoke of the mean tropical year instead of the Vernal
Equinox year, because that synchronization to the Vernal-Equinox year was
only temporary. Though the drift-rate was & is very slow, the difference
between the tropical-year lengths is very slight.

.

When the Gregorian reform was being discussed by Gregorius’ assembled team
of astronomers & mathematicians, some wanted a more accurate rule. But it
was decided that sufficient accuracy is achieved by the one that they
eventually chose. They were right.

.

The French  Republican Calendar  (FRC) is a calendar of terrestrial
seasonal emphasis.

.

Litmus Freeman, a remarkably-talented & creative traveling troubadour &
calendar-advocate in England proposes a calendar structurally-similar to
the FRC.

.

His calendar, like the FRC, is an ecliptic-months calendar that achieves
fixed-ness via blank-days (which I don’t like, but which many
calendar-reform advocates don’t object to).

.

I should just add now that the following 3 calendar-attributes are mutually
incompatible:

.

1. Accurate ecliptic-months

.

2. No blank-days

.

3. Fixed-calendar.

.

Therefore, because I don’t like blank-days, my Ecliptic-Months Calendar
proposal wasn’t a fixed calendar. It was identical to the Indian National
Calendar, but with a different yearstart rule, & Western Zodiacal names for
the ecliptic-months.

.

Anyway, returning to Freeman’s ecliptic-months calendar:

.

It’s called the Universal Celestial Calendar (UCC).  It is indeed
internationally-universal, because it’s celestial.  Its celestial nature is
strongly emphasized.  So one difference between FRC & UCC is that FRC is
terrestrial & UCC is celestial.

.

UCC’s celestial nature is the justification for “Universal” in its name.

.

Other differences:

.

Whereas FRC starts its year at the Autumnal Equinox, UCC starts its year at
the Vernal Equinox.

.

Whereas FRC places all of its blank-days together at the end of the 

Perpetual Calendar of Giovanni Antonio Amedeo Plana

[graham stapleton via sundial]

Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die
eigentliche Nachricht steht dadurch in einem Anhang.

This message was wrapped to be DMARC compliant. The actual message
text is therefore in an attachment.--- Begin Message ---
While calendars are a current topic, please can anyone direct me to detailed 
information about the Perpetual Calendar created by Giovanni Antonio Amedeo 
Plana, located in Turin.
I have discovered a paper: IMEKO-TC4-ARCHAEO-2017-008.pdf but it has few 
details. Apparently the University of Turin team built both a physical replica 
and a digital version, I have not found any references to these.
Graham Stapleton --- End Message ---
---
https://lists.uni-koeln.de/mailman/listinfo/sundial

Francis West and Sons

[Patrick Powers]

Members of this list who follow my 'nearly-weekly' news updates about sundials, 
dialling news and comment and related matters (it can be found at my  'SunInfo' 
webpage which is at www.ppowers.com/sun.htm) will have seen the latest entry 
about the interesting Francis West (1789–1867) sundial that was later moved to 
Frogmore House Gardens in Windsor Great Park from Claremont House in 1931 after 
its purchase by the late Queen Mary. 

Only a little is known about Francis though his business was later grown by his 
sons after his death and they expanded it into many other aspects of 
instrumentation even, it is said, to the design and sale of magic lantern 
slides!  Clearly a go-getting family.  If anyone on this list is able to add 
more either to the life and works of Francis West himself or knows more about 
his sons' follow-on businesses please do let me know.  Thank you for your help.

Patrick Powers---
https://lists.uni-koeln.de/mailman/listinfo/sundial