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I know plate solving is common method in astrophotography for determining where the telescope/camera is pointing at. My question is, can this data (series of plate-solved observations) be used to determine the ground position and date/time of the observation?

I'm thinking hypothetical situation where you are dropped in a random place on Earth with basic amateur telescope with no knowledge of current time or date, can you somehow figure out your location and time? What different approaches are available, and what equipment is needed? I'm primarily interested in stuff that does not rely on having accurate Greenwich time as reference and instead are based solely on observation data.

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    $\begingroup$ In absolute terms, you need precise date and time to determine location. Or precise location to determine date/time. An almanac showing the positions of the stars/planets at a given time is also necessary. The only descent time keeping method, other than a clock, was the "lunar distance" method, and wasn't that precise in practice. $\endgroup$ Commented Jan 17 at 17:17
  • $\begingroup$ I understand that historically the lunar distance inaccuracies stemmed from the difficulties in measurement and the limitations of almanac tables. But with modern astrophotography we can just plate solve the entire field of view, and have access to precision ephemerides. $\endgroup$ Commented Jan 17 at 19:23
  • $\begingroup$ Wikipedia also mentions using galilean moons as reference, which seems interesting. Overall I have a feeling that for modern stationary ground based observations there are lot more possibilities than what was available historically in naval navigation $\endgroup$ Commented Jan 17 at 19:27

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Answer: Yes. both Lunar Distance and Moons of Jupiter can function as a celestial clock. Once time is determined, position can be determined by any of several celestial navigation methods.

For celestial navigation (determining the observer's location on Earth from celestial observations) you need a clock. The clock can be a chronometer or a celestial object which moves in a predictable manner, along with those predictions (the ephemeris). The two celestial clocks traditionally used are the "Moons of Jupiter" and "Lunar Distance".

The "Lunar Distance" refers to the sextant angle between the moon and an index star, not the distance from the observer to the moon. It is a bit tricky since the moon is close enough to the Earth to induce a parallax effect. With practice, it can give time to within a few seconds.

"Moons of Jupiter" refers to the relative positions of the Galilean moons of Jupiter. Paralllax correction is not needed.

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https://medium.com/@domchang/jupiters-moons-and-the-speed-of-light-e86ee8b96d

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You can make a sundial, that will give the local solar time.

You can make an almanac: watch the maximum elevation of the sun over some time and you'll be able to find the days of the solstice, and equinox.

What you can't do is work out the exact clock time, nor the exact calendar date from such measurements. For example, it's impossible to know what timezone you are in, or if that time-zone uses daylight saving time in summer.

Given sufficient time, you could recreate all of human technology from scratch!

It's practically impossible to know exactly what the day of the week is (They are arbitrary), nor the year, and as the date of the equinox changes from year to year (with the leap years) it's not possible to say "It's 9 am on Sunday 19th January 2025".

It might be possible to get some more information by careful observation of the moons of Jupiter, combined with a detailed almanac. A sufficiently long series of observations of the time of eclipses could allow you to work out the exact time and date, but this is not the sort of thing that a time traveller could do with only basic equipment.

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