I was reading about a Patek Phillipe pocket watch that had the complication of the equation of time. What is the equation of time on a watch?

Formally defined as the difference between clock time and apparent solar time.
The equation of time has two causes:
1. the plane of the Earth's equator is inclined to the plane of the Earth's orbit around the Sun
2. the orbit of the Earth around the Sun is an ellipse and not a circle

The total of these two effects gives the equation of time. It is named "equation" because the deviation of time can be described mathematically by the combination of equations describing deviations of time for each effect.

The effect can be observed as clock noon time differing from Sun noon time (sideral time) by as much as 16 minutes. The following graph gives this deviation along the year.
(information from te site of the National Maritime Museum, UK)

Speaking of Pateks, the one on the antiques road show last week was billed as a grand complication. What exactly does that mean? The number of functions? And if so, how many functions constitutes a "grand"? I recall a Patek grand complication built in 1931 that had 28(?) functions; it went at auction for $11+ million(or more?) a few years ago. The one on the ARS had 5 or 6 functions I think....it was a wonderful beauty in mint condition with box and papers and was the presenter's great grandfathers watch. It was valued by the appraiser at $250,000, which I think is a very conservative figure. So, what makes a watch a "grand complication"? The only disapointment in seeing the piece was that there were no shots of the movement....I would pay money to see that!

Hi All,

The Sotheby catalog for December 2, 1999 has pages of great pics of the $11+ million watch which Sam mentions. I purchased a copy of the catalog on ebay.

I think that I bought my copy from the seller who has this auction running;

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=...item=6939523846&rd=1

May be worth asking if he still has any left ?

I could copy and email pics if anyone wants them, but there are lots of them.

My catalog says, in part;
"In 1925, Patek Philippe was commissioned by Henry Graves, a prominent New York banker, to produce the most complicated watch in the world. The product of three years of research and five years’ effort by the most skilled technicians, this extraordinary timepiece features 24 complications including a perpetual calendar, moon phases, sidereal time, power reserve, and indications for time of sunset and sunrise and the night sky of New York City. The watch sold for $11,002,500 to an anonymous bidder over the telephone."
The watch certificate shows No.198,385 serial number

As the Patek Philippe web site shows this numered watch, in their museum section as, "The Supercomplication" The Henry GRAVES Jr. PATEK PHILIPPE & Co, Geneva, N° 198’385 Double open-faced keyless-winding pocket watch with 24 complications:"
It is probable that Patek Philippe was the actual buyer of this piece.

Re equation of time, the catalog says the same as Carlos;
"The equation of time indicator on the Graves watch is calibrated to show the difference between apparent solar time (the time as indicated by a sundial) and mean time (the average of solar time).

Since the Earth is in an elliptical orbit, the difference between mean and solar time ranges from plus 14 minutes 59 seconds to minus 16 minutes 15 seconds.

Solar time agrees with Mean Time on or about April 15, June 15, August 31 and December 24th.
The Graves watch indicates the equation of time on a sector shaped scale with calibrations for plus/minus 17 minutes.

The equation of time mechanism is driven by an arbor that protrudes through the movement from the calendar mechanism."

I have yet to work out why on earth anyone would need a watch showing this particular indication ?

Regards, Barry Parker

Way over my head, but here is a website that might help some. My understanding of it from the story on John Harrison from the TV movie Longitude, if you know the Equation of Time, you can tell where you are located by using the stars and other measurements. When they were out at sea for a long period of time, they would need to know exact directions in order to reach the correct area, or be lost at sea.

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980116c.html

And this link on Longitude:

http://rubens.anu.edu.au/student.projects97/naval/home.htm


Andy

very interesting thread.As for Barry's last question, the only possible answer is "because we can."

The classic definition of Grand Complication is a watch with Split seconds with register plus perpetual calendar showing moon phase and leap year plus minute repeater.

There were quite a few of these made. I think Louis Audemars fitted the complications to English watches and the rest were straight Swiss. They used to show up a couple of times each year at Sotheby's and Christie's auctions.

The equation of time is useful if you want to know where the sun is at any particular time of day (or night). It is much more useful in a clock where the clock and sun dial are near one another. In that case you can use it to set the clock as accurately as your sun dial.

Here is a great little article on Equation of Time, from TimeZone. You can see how watchmakers design the parts to compute and display EOT.

http://www.timezone.com/library/rdnotebook/200503287777

Pete