Watch by Arnold & Son
Because adding a moonphase complication to a mechanical significantly increases the complexity of the wheel train inside the watch vs the standard.
The reasons they are called complications is that the complicate the standard setup of the wheels inside the movement of a watch.
Just to let you know, this is a very basic movement, disassembled, coming from a Timex watch:
A movement disassembled by Timex
If you put it back on, these pieces will give you a fully working watch showing hours, minutes and seconds.
Now, let’s see what happens inside a watch that has a moonphase complication:
Moonphase disc by Patek Philippe (image from thenakedwatchmaker.com)
This is the assembly of wheels and levers needed to drive the moonphase disc ONLY.
Because, to be accurate, such a watch has to reliably track the Moon cycle, and the length of the cycle can vary slightly, but on average, it is 29.53059 days (not a really easy multiplier, for something that is based on precise rapports of wheels). Obviously, the more precise the watch is, the more wheels it will have to feature to correct the anomalies that the cycle has during the year.
For example, take a look at this:
Month corrector wheel by Patek Philippe (image from thenakedwatchmaker.com)
These wheels correct the month in a full calendar watch (in this case, a Patek Philippe).
Complications - full calendar and moonphase - are expensive
If you add up complications inside a watch, like full calendar and moonphase, which is somewhat common, the price to create such a complicated piece of micro-engineering soars, reaching absurd levels of insanity. The ARNOLD & SON HM DOUBLE HEMISPHERE PERPETUAL MOON 1GLAR.U03A.C122A that you see on top has a list price of around $35,000. But you can readily understand why they ask such a price, given how difficult it is to make such a watch.
And if you like this kind of complication, no worries: some of them are equally beautiful and cost much less, like this Frederique Constant FC705X4S4
It is available for $2,200, more or less. Not cheap, but not costing an arm and a leg either.
if you are interested in the different complications of watches, I explain them in layman’s terms in The Watch Manual (buy it here). You can also download a free 42-page sample to check if this is something that you would enjoy reading.
The Watchonomicon is an independent blog, written and managed by The Watch Manual. The Watch Manual is NOT affiliated in any way with any brand mentioned in articles.