Yes, but I don't know if any estimation of refraction or diameter would account
for 20 minutes!
In any case, the real time is scarcely relevant - they only wanted to say that
it was shortly after sunrise, sufficiently so that the Sun was estimated to be
clear of the horizon.
The clock they
Okay, but there's the inaccuracy of the clocks in those days, and the
importance of that would depend on how they determined Sunrise. I guess
they set the clocks by sundial or noon-mark, but, as you said, it depends
on how often they set them.
Anyway, the difference between the NOAA Sunrise-time,
Hi Michael,
Also, when they said that he was born a certain number of minutes after
Sunrise, how did they determine that? By judging when it seemed to be Sunrise,
when the Sun appeared over the trees, mountains or buildings, or by calculating
Sunrise-time based on a 14th century estimate of
Of course, even if the Earth's orbit didn't change, no civil calendar keeps
a constant relation between date and ecliptic-longitude. So you'd have to
determine the calendar's date-ecliptic-longitude displacement for the date
of interest.
.
But the Earth's orbit does change. Our orbit's
Hi Ross,
Are you making Time Zone adjustments?. When I start Stellarium, by
default it uses my own time zone even if I change location. I have to go
to the Plugins and explicitly set a time zone. I imagine you should be
working in the local time of Milan, which I estimated roughly at (9.2
Hi diallists,
This is not a sundial problem, but a time discrepancy I don't understand
between NOAA sunrise calculations and the results of two reliable planetarium
programs, Stellarium and YourSky (part of HomePlanet). http://stellarium.org/
https://www.fourmilab.ch/yoursky/
