Hello again,
Here is the complete data with the exception of the first three months
which have been lost:
April 1793 - sunrise: 5:20 and sunset: 07:14
- day length - 13 hours and 20 minutes, night - 10
hours and 40 minutes
May 1793 - sunrise: 4:33 and sunset: 07:47
- day length - 14 hours and 54 minutes, night - 9
hours and 6 minutes
June 1793 - sunrise: 4:05 and sunset: 07:47
- day length - 14 hours and 53 minutes, night - 9
hours and 7 minutes
July 1793 - sunrise: 4:12 and sunset: 07:44
- day length - 15 hours and 36 minutes, night - 8
hours and 24 minutes
August 1793 - sunrise: 4:51 and sunset: 06:39
- day length - 14 hours and 18 minutes, night - 9
hours and 42 minutes
September 1793 - sunrise: 5:41 and sunset: 05:29
- day length - 12 hours and 38 minutes, night -11
hours and 22 minutes
October 1793 - sunrise: 6:24 and sunset: 05:20
- day length - 10 hours and 52 minutes, night - 13
hours and 8 minutes
November 1793 - sunrise: 7:24 and sunset: 04:21
- day length - 9 hours and 12 minutes, night - 14
hours and 38 minutes
December 1793 - sunrise: 7:54 pm and sunset: 4:05 pm
- day length - 8 hours and 12 minutes, night - 8
hours and 48 minutes
Dan Uza
On Fri, Aug 9, 2019 at 10:50 PM Dan-George Uza
<cerculdest...@gmail.com <mailto:cerculdest...@gmail.com>> wrote:
Dear Steve,
I will share the data for the whole year once I get it (I only
have April). Your preliminary results sound too good to be true.
I did a simulation using TimeAndDate.com for three completely
different locations on the European continent: Constanta
(Romania), Gorlitz (Germany) and London (UK). I chose these
because of their proximity to the time zone meridians, this way
the old solar time is more easily found (I just exclude 1h
daylight saving time).
The stated duration of the day of 13h20min for April is recorded
in those localities on April 13, April 7, respectively April 7
(all gregorian, the last two cities have approximately the same
latitude).
Sunrise on these respective dates (in solar time): 5:24 in
Constanta, 5:23 in Gorlitz, 5:23 in London.
Sunset (in solar time): 18:47 at Constanta, 18:42 at Gorlitz,
18:43 at London.
In the calendar we've got sunrise at 5:20, which is a good enough
fit for all the above examples.
On the other hand, sunset is at 7:14 (p.m.) and this time doesn't
fit any of the examples above.
If we consider it to be the civil twilight, we have 19:16 for
Constanta, 19:16 for Gorlitz, respectively 19:17 for London (old
hours). These correspond quite well with the sunset given by the
calendar.
Dan Uza
On Fri, Aug 9, 2019 at 10:15 PM Steve Lelievre
<steve.lelievre.can...@gmail.com
<mailto:steve.lelievre.can...@gmail.com>> wrote:
Dan,
Using only your April data, and assuming:
1. day length is the difference of the sunset and sunrise (as
opposed to the daylength stated),
2. sunrise and sunset are when the center of the sun is on the
horizon
3. my modern source of solar declination data is "good enough"
4. your table of values is for the Julian calendar, which for
the year in question is offset from the Gregorian calendar by
11 days,
then, by varying latitude to minimize the Sum of Squares of
the differences between true day lengths and the
representative day length stated .... I get a latitude of
44.413N, which would correspond to Bucarest.
If I could use your table of data for the full year, the
result would of course be different - better, I would hope,
but possibly not!
As yet, I have no idea why the stated day length is not the
same as the difference of the sunrise and sunset.
Steve
On 2019-08-09 1:06 a.m., Dan-George Uza wrote:
Hello all,
I have seen an old calendar from 1793 which lists for every
month sunrise and sunset times as well as day and night
duration. For example, taking the month of April: sunrise at
5 h 20 m, sunset at 7 h 14 m; day length 13 h 20 min, night
length 10 h 40 m.
Somebody asked me if it would be possible to establish the
approximate geographical area for these predictions.
I'm pretty sure it's not possible. Back then they used true
solar time (or perhaps mean solar time?) so I guess these
hours would have been valid for a whole parallel of latitude,
with variations once you go north or south.
Nevertheless, I made a simulation and realized that I cannot
get close to these numbers. I don't know why. Perhaps because
back then sunrise and sunset was not counted by solar limb,
but by geometric center of the Sun? How did they do it?
Regards,
--
Dan-George Uza
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