Re: What did the night sky look like on the 1st Independence Day 250 years ago?

"a425couple"  wrote in message news:[email protected]...

But first, how did people in 1776 keep track of astronomical phenomena?
People studied astronomy for practical reasons both in and out of the
classroom. It was essential for navigation, surveying, timekeeping, and
charting unfamiliar lands. In an age before light pollution, ordinary
people were also likely far more familiar with the stars and
constellations than most people are today.

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The sun, moon and stars are all directly overhead at some spot on Earth, and 
that spot can be determined from an almanac's data, the time, and a 
measurement of the object's elevation angle above the horizon, or 
equivalently half its elevation from its reflection in water or mercury. The 
angle from the object to straight above you gives your distance from that 
spot, at 69.17 land miles per degree, or 60.0 nautical miles.
https://aa.usno.navy.mil/data/Nav_Star_Chart

Learning the pattern permits identifying stars visible in cloud gaps.

For practical reasons navigation is usually done differently, by longitude 
and latitude which matches chart grid markings.
https://en.wikipedia.org/wiki/Sextant

The telescope on the sextant is powerful enough to show the sun moving, 
especially when it changes from rising to falling which is your local noon. 
The time difference between your observed noon and noon at longitude 0, the 
observatory at Greenwich UK, gives your longitude at the rate of 15 degrees 
per hour.

https://www.rmg.co.uk/stories/time/harrisons-clocks-longitude-problem
Only a century earlier the most accurate time keepers were still the 
dripping water clocks of the ancient Greeks.

One of many lingering mysteries of the Titanic is why its distress call 
position report was so far off in longitude, first 20 and then "corrected" 
to 13 miles to the west, while its latitude was accurate within a mile. 
Ships responding to the call were directed to a place over the horizon, on 
the far side of the iceberg field. No one realized this until Ballard found 
the wreck and a tightly clustered debris field of heavy compact boilers that 
fell out and sank straight down when the hull broke in half at the surface.

Luckily for the freezing survivors a nearby ship was to the southeast and 
approached the ice field on their side. That ship had been headed for 
Gibraltar, which shows how far south the ice had drifted.