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0
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1answer
56 views

How accurately can you tell the time using a photo of the stars?

If I were to go out on a clear night, in an area with low light pollution, and take a photo of the stars, could an expert analyze the photo and figure out what date the photo is from? We can assume a ...
4
votes
1answer
47 views

How Soon Could a Waxing Crescent Moon Be Seen?

Question: Apart from a Solar Eclipse, How much time is needed until a Waxing Crescent Moon be seen following a New Moon? Would the time of year be significant? The Vernal Equinox + 1 Month. ...
6
votes
1answer
56 views

Is there a variation of ISO 8601 for julian calendar dates?

If I want to write a date in the Gregorian calendar, I can write it in the ISO 8601 format; today would be 2016-02-20. The advantage is that there are many parsers available to let computers read in ...
1
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0answers
26 views

About bias in sidereal time (used by astronomers)

I came up on this stanza in various websites when looking up on experimenter bias. It says "If the signal being measured is actually smaller than the rounding error and the data are over-averaged, a ...
4
votes
2answers
144 views

How does the appearance of the analemma vary with latitude

How does the appearance of an analemma vary with latitude? This what I take to be a definition of an analemma: If the position of the sun is plotted or photographed at noon clock time (say UTC) every ...
4
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2answers
71 views

September 26 twelve hours sunrise to sunset?

I noticed in today's newspaper (Boston Globe, September 26) that sunrise and sunset were both at 6:25. That's the twelve hour day I'd have expected at the equinox. (Please retag if there's a better ...
10
votes
4answers
2k views

How can we avoid needing a leap year/second?

Given the Earth's current speed around the sun and current rate & axis of rotation, what is the best way to keep time to avoid a leap year? How many hours should we have in the day and days in a ...
4
votes
1answer
109 views

Determining North-South Line Via Watch Method: Theory & Reason

I recently read that if you're in the northern hemisphere and have an analog watch, then you can point the hour hand at the sun and know that a south line lies between (bisection) the hour hand and ...
1
vote
1answer
38 views

How could eclipse happen on the same day in a different calendar? (45 AD)

According to the eclipse calculator I use (Alcyone), a partial eclipse 0.314 magnitude occurred August 1, 45 A.D. in Rome starting at 8:35am local time. This would seem to correspond to an eclipse ...
1
vote
1answer
59 views

What's the difference between the Julian and the Julian Ephemeris Day?

I'm making a code where I calculate the sun position in a given time. But I also want to learn astronomy with it. I'm following a .pdf to make the program, and in this .pdf it says The Julian Day ...
0
votes
1answer
57 views

what is the time mentioned after date (1962-07-03+02:00) the +02:00? [closed]

i was retrieving a some personalities birthday date through computer programming when i retrieve a person's birthday the result was ...
5
votes
0answers
116 views

How to calculate geocentric conjunction time and moon altitude at a given time

Umm al-Qura calendar of Saudi Arabia determine the new moon if these criteria meet at 29th day: The geocentric conjunction occurs before sunset. The moon sets after the sun. I've got the formula ...
2
votes
1answer
132 views

Day Length on Double Planets

Assume two similarly sized bodies tide-locked to one another orbiting a barycenter between the two. That barycenter orbits a star. Since the two are tide-locked, their sidereal rotational period and ...
1
vote
3answers
217 views

Years, Months, Day, and Weeks?

Sorry if this is a basic question. 1 year = earth revolution around the sun 1 month = moon revolution around the earth 1 week = 7 days = ??? 1 day = earth rotation about its axis Why do we ...
1
vote
2answers
343 views

Find constellation over Earth coordinates on a specific date-time

I would like some help in finding the exact constellations, or some sort of visualization of the stars over an specific location an time. The idea is to find out the closest star or group of stars on ...
1
vote
1answer
174 views

When will a day on Earth & Mars be the same length?

I read on Wikipedia that: As on Earth, the period of rotation of Mars (the length of its day) is slowing down. However, this effect is three orders of magnitude smaller than on Earth because the ...
0
votes
1answer
185 views

Calculate the time when Arcturus passed through the meridian

If the observer observes Arcturus passed through the meridian about 23:00:00 of 28 April. Find the time that Arcturus passed the meridian in 29 April. And what day does the Arcturus will pass the ...
1
vote
1answer
167 views

Why do we need to add a second to 30 June and risk upsetting Internet?

We linked a physical constant (the time of one second) to a physical non constant (the rotation of the earth) so there will have to be adjustments - or not? Is it important that the UTC in one line on ...
1
vote
2answers
53 views

How often and over what period is Earth’s rotation averaged to compute UT1?

I understand that UT1 (and for that matter UT0, UT2, etc.) are based on averages of actual earth rotation, and serve as a form of mean solar time. However it’s not clear to me when these averages are ...
2
votes
1answer
142 views

During what time of the year can Centaurus be seen from Tokyo?

During exactly what dates of the year can the Centaurus constellation be seen from Tokyo, Japan? And what is the ideal date for viewing it from Tokyo? I found on a website that it can been seen ...
6
votes
2answers
421 views

Is it possible for a person to not see the new moon at different places on earth?

It is known that theoretically we see the same moon phase everywhere on the earth, but practically I see that people are unable to observe the 0.8% waxing crescent at different places on earth. This ...
2
votes
3answers
101 views

Date and time system on moons

Supposedly, if humans were to establish a colony on one of the moons of a planet (such as gas giants in our own solar system), how could we possibly design date and time system? On Earth, we define ...
4
votes
3answers
170 views

Is sundial time entirely dependent on solar azimuth?

I've visited several "how sundials work" sites and can't seem to get a clear answer to this: is "sundial time" just a linear function of solar azimuth? More specifically: When the sun is due ...