Full moon

Hello everyone,

I am new to the forum but not new to IWC. I bought my first IWC - a Venezia (2552) in the 90s - and recently added a hand-wound Portofino (5448). I was hoping this purchase would reduce my incentives to engage in watch-related internet "research". Unfortunately, the opposite is the case. That's how I discovered this informative and entertaining forum.

By now you might have an idea where my alias (8000) comes from. Remember, in some parts of the world 8 is a lucky number. I plan to show some pictures of my two IWC beauties in near future. I hope you don't mind.

Today is full moon. I took the opportunity to align the moon phase indication of my 5448 with the actual moon phase for the first time. I noticed that I cannot exactly center the moon disc on my dial. The disc either touches the left or the right "mountain" of the moon phase display. It will never sit exactly between these two mountains.

I wonder if this is normal. Any comments would be highly appreciated.

Best regards from down under (Melbourne),

Jim

Ok, I think I found the answer myself. Given the following two conditions

1) full moon occurs every 29.53 days
2) the moon phase indication is not continuous but advances in discrete steps at midnight

it must be pure coincidence if the moon disc is fully centered on the display at full moon.

In my opinion, this also means that the published 122 years accuracy for the 5448 only holds if the watch has been more or less continuously running since IWC calibrated the moon phase during production. It is more a hypothetical accuracy because almost everyone will have periods in which the watch is not running (if not you then maybe the dealer from which you bought the watch).

For example, when I align the moon phase of my watch today, I don't know if this is the, e.g., 22nd full moon after IWC calibrated the watch or the 27th full moon. Thus, I will make an error which reduces the 122 years accuracy. Even if I would know that the watch was not running for a period of, say, 5 full moons, I am unlikely to move the moon forward by 5 months (way too much winding).

The situation is better for a perpetual calendar. Because a perpetual calendar also display the correct date, it is guaranteed that the moon phase indication always corresponds to the current date. In this case, the published accuracy of the moon phase indication should be achievable in reality. The problem of too much winding after a lengthy period of not using the watch remains (I know there are winders for automatic watches).

Sorry, for my lengthy notes. I hope I did not bore you. Personally, I find these observations quite interesting. Please let me know if you agree or disagree.

Finally, let me say that these observations do not affect at all my enthusiasm about the 5448. It is a gorgeous watch and at the end I must confess that I like the moon phase display mostly for aesthetical reasons.

Best regards,

Jim

Sounds like you fully understand the issue with the "resolution" of the moon phase.

With regard to the 122 year moon phase accuracy - I do not believe that this holds true for your Portofino Moonphase - since there are no other calendar functions that need to be synched to it -

If you set the watch to the full moon today - and keep in wound, and running for the next 122 years - it will be one day off on 17 FEB, 2133. So the 122 years will start for you TODAY. If you let the watch stop, and you reset the moonphase in a couple weeks - the 122 years will start over again...

In the case of a perpetual calendar watch - the moon phase is set, and synched, statically, to the day, date, month, year etc - so perpetual calendar owners cannot set the moon phase independently of the date. We will need to send it to IWC Service for that - when the time comes - in 577 years for the Portuguese Perpetual Calendar.

"If you set the watch to the full moon today - and keep in wound, and running for the next 122 years - it will be one day off on 17 FEB, 2133. So the 122 years will start for you TODAY."

Thank you, Ardoise, I agree with you. The only small problem is that the starting position of the moon disc is probably not exactly right today while it probably was exactly correct when it was calibrated by IWC. But these are really just academic differences. Conditional on the starting position, the 122-year accuracy will indeed hold. I am glad, I understood this with your help.

Best, Jim

[QUOTE="8000" The only small problem is that the starting position of the moon disc is probably not exactly right today while it probably was exactly correct when it was calibrated by IWC.[/QUOTE]

Jim - I forgot to respond to this concern of yours originally. Your moon phase disc is set correctly, or at least, consistently with my 4 IWC Perpetuals with moon phase displays. This is really done for more convenience and accuracy of the display.

You must realize that although yesterday was indicated as a "full moon" - the actual moon is not full for a complete 24 hours - it is 100% full for only a brief moment. A fraction of a second. We simply indicate the date that this 100% occurs on our calendars. To the naked eye, the moon may appear full the day before, or day after - so, (this is my opinion) IWC applied the best case scenario.