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 <[email protected]>
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 <
> [email protected]> 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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>>
>>
>> ---------------------------------------------------
>> https://lists.uni-koeln.de/mailman/listinfo/sundial
>>
>>
>
> --
> Dan-George Uza
>
--
Dan-George Uza
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