Hi Been there done that. Rest of the family was more impressed by the view than by the chronometers ...
Bob On Nov 4, 2010, at 8:19 PM, Bob Marinelli wrote: > Hi Bill, > > The astronomers were busy doing their noon transit sighting at noon. They > ball on Flamsteed House drops at 1:00. The navigators on ships in the harbor > were also likely doing a sight at noon, they set their clock at 1:00 by > looking up at the observatory on the hill. BTW, the view from Greenwich > observatory over London is quite spectacular. The above my recollection from > a tour guide at the observatory. Here is the official story (including an > animation of the ball dropping): > > http://www.nmm.ac.uk/places/royal-observatory/time-ball/ > > I guess this is the time to propose that, if possible, every Time Nut needs > to visit Greenwich Observatory at least once :) > > -Bob > > On Nov 4, 2010, at 5:11 PM, WB6BNQ wrote: > >> OK Bob, >> >> I'LL bite ! Why is it 1:00 pm for the ball ? >> >> Bill....WB6BNQ >> >> >> Bob Marinelli wrote: >> >>> Hi Murray, >>> >>> Actually, the ball at Greenwich drops at 1:00 pm every day. For >>> everyone who can get to London, the observatory is well worth at least >>> a half day visit, they have several working Harrison clocks and yes >>> you can set your wristwatch at 1:00 when the ball drops :) there is >>> also a wonderful transit. >>> >>> Cheers, >>> >>> Bob >>> >>> On Nov 4, 2010, at 4:30 PM, Murray Greenman wrote: >>> >>>> Navigators used chronometers to determine their longitude. If they >>>> were >>>> stopped in one place long enough, they could work out longitude by a >>>> complicated process of star and lunar observations; however, when they >>>> left an established port, they usually took with them a time standard >>>> based on local measurements of the sun and the known location of the >>>> port. >>>> >>>> These measurements used a device called a 'Transit', which was a >>>> simple >>>> telescope mounted so that it pivoted in elevation, but was fixed N-S >>>> in >>>> azimuth. Midday was marked by the time at which the sun transited the >>>> telescope. It thus had higher resolution than a sundial. Getting N-S >>>> axis correct involved determining by iteration and surveying the axis >>>> that gave maximum elevation at time of transit. >>>> >>>> Once the transit was observed, a large ball on top of the building was >>>> dropped, indicating midday, and in some locations a cannon was also >>>> fired. Ships in port could observe the ball drop and hear the >>>> cannon. To >>>> this day the ball drops at midday at Greenwich. >>>> >>>> >>>> 73, >>>> Murray ZL1BPU >>>> >>>> >>>> _______________________________________________ >>>> 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. >> >> >> _______________________________________________ >> 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. _______________________________________________ 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.
