Is the USNO almana/ephemeris still published in hard copy every year? That had moon timing, etc.
-John =============== -John ================ > >> But how do you untangle longitude and time? How do you know that you are >> looking exactly south (or north)? > > If I understand what you are asking, it's the same problem as navigating a > ship without a clock. > > Classic navigation with a sextant needs a clock and sightings on 3 objects > in > the sky. Each sighting gives you a circle on the globe, or a line if you > know roughly where you are. The lines form a triangle. The size of the > triangle is an indication of the accuracy. You pick the objects so the > triangle is roughly equilateral. > http://en.wikipedia.org/wiki/Celestial_navigation > You can get time from the moon, so in theory at least, that's an answer to > your question. > http://en.wikipedia.org/wiki/Lunar_distance_%28navigation%29 > > Years ago, when a friend was learning navigation, he was reading one of > the > old classic texts. There was a good story about the guy off the coast of > England/Ireland who didn't trust his clock, so he did the calculations > again > assuming his clock was a bit fast and again with it slow. That gave him 3 > parallel lines for each sighting. Anybody recognize that story? > > > Longitude by Dava Sobel is a good read, especially for time-nuts. There > is > also a version with lots of good photographs. > > One of the techniques they actually considered before Harrison built good > enough clocks was to derive time from Jupiter's moons. They knew enough > to > correct for the time shift due to speed of light delays as the > Earth-Jupiter > distance changed. (I don't know if they knew if was due to speed of > light.) > > You can synchronize two clocks if both sites can see the same event in the > sky, Occultations are often used for this. > > With modern technology, radio telescopes are very very good at this. In > order to do VLBI, you need to know where the telescopes are located. With > a > big collection of data you can do least-squared fit type calculations to > refine the location and clock calibration. > > -- > These are my opinions, not necessarily my employer's. I hate spam. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
